stlink: remove reset pulse when entering in JTAG
[fw/openocd] / src / jtag / drivers / stlink_usb.c
index 708b24b41c8fc00056453dc42dc5e6209b1e1847..f05ffadf9e1896257426df3252ba2c7a318286d5 100644 (file)
@@ -1,7 +1,14 @@
 /***************************************************************************
+ *   SWIM contributions by Ake Rehnman                                     *
+ *   Copyright (C) 2017  Ake Rehnman                                       *
+ *   ake.rehnman(at)gmail.com                                              *
+ *                                                                         *
  *   Copyright (C) 2011-2012 by Mathias Kuester                            *
  *   Mathias Kuester <kesmtp@freenet.de>                                   *
  *                                                                         *
+ *   Copyright (C) 2012 by Spencer Oliver                                  *
+ *   spen@spen-soft.co.uk                                                  *
+ *                                                                         *
  *   This code is based on https://github.com/texane/stlink                *
  *                                                                         *
  *   This program is free software; you can redistribute it and/or modify  *
@@ -15,9 +22,7 @@
  *   GNU General Public License for more details.                          *
  *                                                                         *
  *   You should have received a copy of the GNU General Public License     *
- *   along with this program; if not, write to the                         *
- *   Free Software Foundation, Inc.,                                       *
- *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
+ *   along with this program.  If not, see <http://www.gnu.org/licenses/>. *
  ***************************************************************************/
 
 #ifdef HAVE_CONFIG_H
 /* project specific includes */
 #include <helper/binarybuffer.h>
 #include <jtag/interface.h>
-#include <jtag/stlink/stlink_layout.h>
-#include <jtag/stlink/stlink_transport.h>
-#include <jtag/stlink/stlink_interface.h>
+#include <jtag/hla/hla_layout.h>
+#include <jtag/hla/hla_transport.h>
+#include <jtag/hla/hla_interface.h>
 #include <target/target.h>
 
 #include <target/cortex_m.h>
 
 #include "libusb_common.h"
 
-#define ENDPOINT_IN    0x80
-#define ENDPOINT_OUT   0x00
+#define ENDPOINT_IN  0x80
+#define ENDPOINT_OUT 0x00
+
+#define STLINK_WRITE_TIMEOUT 1000
+#define STLINK_READ_TIMEOUT 1000
+
+#define STLINK_NULL_EP        0
+#define STLINK_RX_EP          (1|ENDPOINT_IN)
+#define STLINK_TX_EP          (2|ENDPOINT_OUT)
+#define STLINK_TRACE_EP       (3|ENDPOINT_IN)
+
+#define STLINK_V2_1_TX_EP     (1|ENDPOINT_OUT)
+#define STLINK_V2_1_TRACE_EP  (2|ENDPOINT_IN)
+
+#define STLINK_SG_SIZE        (31)
+#define STLINK_DATA_SIZE      (4096)
+#define STLINK_CMD_SIZE_V2    (16)
+#define STLINK_CMD_SIZE_V1    (10)
+
+#define STLINK_V1_PID         (0x3744)
+#define STLINK_V2_PID         (0x3748)
+#define STLINK_V2_1_PID       (0x374B)
+#define STLINK_V2_1_NO_MSD_PID  (0x3752)
+
+/* the current implementation of the stlink limits
+ * 8bit read/writes to max 64 bytes. */
+#define STLINK_MAX_RW8         (64)
 
-#define STLINK_NULL_EP         0
-#define STLINK_RX_EP           (1|ENDPOINT_IN)
-#define STLINK_TX_EP           (2|ENDPOINT_OUT)
-#define STLINK_SG_SIZE         (31)
-#define STLINK_DATA_SIZE       (4*128)
-#define STLINK_CMD_SIZE_V2     (16)
-#define STLINK_CMD_SIZE_V1     (10)
+/* "WAIT" responses will be retried (with exponential backoff) at
+ * most this many times before failing to caller.
+ */
+#define MAX_WAIT_RETRIES 8
 
 enum stlink_jtag_api_version {
        STLINK_JTAG_API_V1 = 1,
@@ -60,8 +87,10 @@ struct stlink_usb_version {
        int jtag;
        /** */
        int swim;
-       /** highest supported jtag api version */
-       enum stlink_jtag_api_version jtag_api_max;
+       /** jtag api version supported */
+       enum stlink_jtag_api_version jtag_api;
+       /** one bit for each feature supported. See macros STLINK_F_* */
+       uint32_t flags;
 };
 
 /** */
@@ -71,6 +100,12 @@ struct stlink_usb_handle_s {
        /** */
        struct libusb_transfer *trans;
        /** */
+       uint8_t rx_ep;
+       /** */
+       uint8_t tx_ep;
+       /** */
+       uint8_t trace_ep;
+       /** */
        uint8_t cmdbuf[STLINK_SG_SIZE];
        /** */
        uint8_t cmdidx;
@@ -79,81 +114,149 @@ struct stlink_usb_handle_s {
        /** */
        uint8_t databuf[STLINK_DATA_SIZE];
        /** */
-       enum stlink_transports transport;
+       uint32_t max_mem_packet;
+       /** */
+       enum hl_transports transport;
        /** */
        struct stlink_usb_version version;
        /** */
        uint16_t vid;
        /** */
        uint16_t pid;
-       /** this is the currently used jtag api */
-       enum stlink_jtag_api_version jtag_api;
+       /** */
+       struct {
+               /** whether SWO tracing is enabled or not */
+               bool enabled;
+               /** trace module source clock */
+               uint32_t source_hz;
+       } trace;
+       /** reconnect is needed next time we try to query the
+        * status */
+       bool reconnect_pending;
 };
 
-#define STLINK_DEBUG_ERR_OK                    0x80
-#define STLINK_DEBUG_ERR_FAULT                 0x81
-#define STLINK_CORE_RUNNING                    0x80
-#define STLINK_CORE_HALTED                     0x81
-#define STLINK_CORE_STAT_UNKNOWN               -1
-
-#define STLINK_GET_VERSION                     0xF1
-#define STLINK_DEBUG_COMMAND                   0xF2
-#define STLINK_DFU_COMMAND                     0xF3
-#define STLINK_SWIM_COMMAND                    0xF4
-#define STLINK_GET_CURRENT_MODE                        0xF5
-
-#define STLINK_DEV_DFU_MODE                    0x00
-#define STLINK_DEV_MASS_MODE                   0x01
-#define STLINK_DEV_DEBUG_MODE                  0x02
-#define STLINK_DEV_SWIM_MODE                   0x03
-#define STLINK_DEV_BOOTLOADER_MODE             0x04
-#define STLINK_DEV_UNKNOWN_MODE                        -1
-
-#define STLINK_DFU_EXIT                                0x07
-
-#define STLINK_SWIM_ENTER                      0x00
-#define STLINK_SWIM_EXIT                       0x01
-
-#define STLINK_DEBUG_ENTER_JTAG                        0x00
-#define STLINK_DEBUG_GETSTATUS                 0x01
-#define STLINK_DEBUG_FORCEDEBUG                        0x02
-#define STLINK_DEBUG_APIV1_RESETSYS            0x03
-#define STLINK_DEBUG_APIV1_READALLREGS         0x04
-#define STLINK_DEBUG_APIV1_READREG             0x05
-#define STLINK_DEBUG_APIV1_WRITEREG            0x06
-#define STLINK_DEBUG_READMEM_32BIT             0x07
-#define STLINK_DEBUG_WRITEMEM_32BIT            0x08
-#define STLINK_DEBUG_RUNCORE                   0x09
-#define STLINK_DEBUG_STEPCORE                  0x0a
-#define STLINK_DEBUG_APIV1_SETFP               0x0b
-#define STLINK_DEBUG_READMEM_8BIT              0x0c
-#define STLINK_DEBUG_WRITEMEM_8BIT             0x0d
-#define STLINK_DEBUG_APIV1_CLEARFP             0x0e
-#define STLINK_DEBUG_APIV1_WRITEDEBUGREG       0x0f
-#define STLINK_DEBUG_APIV1_SETWATCHPOINT       0x10
-
-#define STLINK_DEBUG_ENTER_JTAG                        0x00
-#define STLINK_DEBUG_ENTER_SWD                 0xa3
-
-#define STLINK_DEBUG_APIV1_ENTER               0x20
-#define STLINK_DEBUG_EXIT                      0x21
-#define STLINK_DEBUG_READCOREID                        0x22
-
-#define STLINK_DEBUG_APIV2_ENTER               0x30
-#define STLINK_DEBUG_APIV2_READ_IDCODES                0x31
-#define STLINK_DEBUG_APIV2_RESETSYS            0x32
-#define STLINK_DEBUG_APIV2_READREG             0x33
-#define STLINK_DEBUG_APIV2_WRITEREG            0x34
-#define STLINK_DEBUG_APIV2_WRITEDEBUGREG       0x35
-#define STLINK_DEBUG_APIV2_READDEBUGREG        0x36
-
-#define STLINK_DEBUG_APIV2_READALLREGS         0x3A
-#define STLINK_DEBUG_APIV2_GETLASTRWSTATUS     0x3B
-#define STLINK_DEBUG_APIV2_DRIVE_NRST          0x3C
-
-#define STLINK_DEBUG_APIV2_DRIVE_NRST_LOW      0x00
-#define STLINK_DEBUG_APIV2_DRIVE_NRST_HIGH     0x01
-#define STLINK_DEBUG_APIV2_DRIVE_NRST_PULSE    0x02
+#define STLINK_SWIM_ERR_OK             0x00
+#define STLINK_SWIM_BUSY               0x01
+#define STLINK_DEBUG_ERR_OK            0x80
+#define STLINK_DEBUG_ERR_FAULT         0x81
+#define STLINK_SWD_AP_WAIT             0x10
+#define STLINK_SWD_AP_FAULT            0x11
+#define STLINK_SWD_AP_ERROR            0x12
+#define STLINK_SWD_AP_PARITY_ERROR     0x13
+#define STLINK_JTAG_WRITE_ERROR        0x0c
+#define STLINK_JTAG_WRITE_VERIF_ERROR  0x0d
+#define STLINK_SWD_DP_WAIT             0x14
+#define STLINK_SWD_DP_FAULT            0x15
+#define STLINK_SWD_DP_ERROR            0x16
+#define STLINK_SWD_DP_PARITY_ERROR     0x17
+
+#define STLINK_SWD_AP_WDATA_ERROR      0x18
+#define STLINK_SWD_AP_STICKY_ERROR     0x19
+#define STLINK_SWD_AP_STICKYORUN_ERROR 0x1a
+
+#define STLINK_CORE_RUNNING            0x80
+#define STLINK_CORE_HALTED             0x81
+#define STLINK_CORE_STAT_UNKNOWN       -1
+
+#define STLINK_GET_VERSION             0xF1
+#define STLINK_DEBUG_COMMAND           0xF2
+#define STLINK_DFU_COMMAND             0xF3
+#define STLINK_SWIM_COMMAND            0xF4
+#define STLINK_GET_CURRENT_MODE        0xF5
+#define STLINK_GET_TARGET_VOLTAGE      0xF7
+
+#define STLINK_DEV_DFU_MODE            0x00
+#define STLINK_DEV_MASS_MODE           0x01
+#define STLINK_DEV_DEBUG_MODE          0x02
+#define STLINK_DEV_SWIM_MODE           0x03
+#define STLINK_DEV_BOOTLOADER_MODE     0x04
+#define STLINK_DEV_UNKNOWN_MODE        -1
+
+#define STLINK_DFU_EXIT                0x07
+
+/*
+       STLINK_SWIM_ENTER_SEQ
+       1.3ms low then 750Hz then 1.5kHz
+
+       STLINK_SWIM_GEN_RST
+       STM8 DM pulls reset pin low 50us
+
+       STLINK_SWIM_SPEED
+       uint8_t (0=low|1=high)
+
+       STLINK_SWIM_WRITEMEM
+       uint16_t length
+       uint32_t address
+
+       STLINK_SWIM_RESET
+       send syncronization seq (16us low, response 64 clocks low)
+*/
+#define STLINK_SWIM_ENTER                  0x00
+#define STLINK_SWIM_EXIT                   0x01
+#define STLINK_SWIM_READ_CAP               0x02
+#define STLINK_SWIM_SPEED                  0x03
+#define STLINK_SWIM_ENTER_SEQ              0x04
+#define STLINK_SWIM_GEN_RST                0x05
+#define STLINK_SWIM_RESET                  0x06
+#define STLINK_SWIM_ASSERT_RESET           0x07
+#define STLINK_SWIM_DEASSERT_RESET         0x08
+#define STLINK_SWIM_READSTATUS             0x09
+#define STLINK_SWIM_WRITEMEM               0x0a
+#define STLINK_SWIM_READMEM                0x0b
+#define STLINK_SWIM_READBUF                0x0c
+
+#define STLINK_DEBUG_GETSTATUS             0x01
+#define STLINK_DEBUG_FORCEDEBUG            0x02
+#define STLINK_DEBUG_APIV1_RESETSYS        0x03
+#define STLINK_DEBUG_APIV1_READALLREGS     0x04
+#define STLINK_DEBUG_APIV1_READREG         0x05
+#define STLINK_DEBUG_APIV1_WRITEREG        0x06
+#define STLINK_DEBUG_READMEM_32BIT         0x07
+#define STLINK_DEBUG_WRITEMEM_32BIT        0x08
+#define STLINK_DEBUG_RUNCORE               0x09
+#define STLINK_DEBUG_STEPCORE              0x0a
+#define STLINK_DEBUG_APIV1_SETFP           0x0b
+#define STLINK_DEBUG_READMEM_8BIT          0x0c
+#define STLINK_DEBUG_WRITEMEM_8BIT         0x0d
+#define STLINK_DEBUG_APIV1_CLEARFP         0x0e
+#define STLINK_DEBUG_APIV1_WRITEDEBUGREG   0x0f
+#define STLINK_DEBUG_APIV1_SETWATCHPOINT   0x10
+
+#define STLINK_DEBUG_ENTER_JTAG_RESET      0x00
+#define STLINK_DEBUG_ENTER_SWD_NO_RESET    0xa3
+#define STLINK_DEBUG_ENTER_JTAG_NO_RESET   0xa4
+
+#define STLINK_DEBUG_APIV1_ENTER           0x20
+#define STLINK_DEBUG_EXIT                  0x21
+#define STLINK_DEBUG_READCOREID            0x22
+
+#define STLINK_DEBUG_APIV2_ENTER           0x30
+#define STLINK_DEBUG_APIV2_READ_IDCODES    0x31
+#define STLINK_DEBUG_APIV2_RESETSYS        0x32
+#define STLINK_DEBUG_APIV2_READREG         0x33
+#define STLINK_DEBUG_APIV2_WRITEREG        0x34
+#define STLINK_DEBUG_APIV2_WRITEDEBUGREG   0x35
+#define STLINK_DEBUG_APIV2_READDEBUGREG    0x36
+
+#define STLINK_DEBUG_APIV2_READALLREGS     0x3A
+#define STLINK_DEBUG_APIV2_GETLASTRWSTATUS 0x3B
+#define STLINK_DEBUG_APIV2_DRIVE_NRST      0x3C
+
+#define STLINK_DEBUG_APIV2_START_TRACE_RX  0x40
+#define STLINK_DEBUG_APIV2_STOP_TRACE_RX   0x41
+#define STLINK_DEBUG_APIV2_GET_TRACE_NB    0x42
+#define STLINK_DEBUG_APIV2_SWD_SET_FREQ    0x43
+#define STLINK_DEBUG_APIV2_JTAG_SET_FREQ   0x44
+
+#define STLINK_DEBUG_APIV2_READMEM_16BIT   0x47
+#define STLINK_DEBUG_APIV2_WRITEMEM_16BIT  0x48
+
+#define STLINK_DEBUG_APIV2_DRIVE_NRST_LOW   0x00
+#define STLINK_DEBUG_APIV2_DRIVE_NRST_HIGH  0x01
+#define STLINK_DEBUG_APIV2_DRIVE_NRST_PULSE 0x02
+
+#define STLINK_TRACE_SIZE               4096
+#define STLINK_TRACE_MAX_HZ             2000000
 
 /** */
 enum stlink_mode {
@@ -165,25 +268,69 @@ enum stlink_mode {
        STLINK_MODE_DEBUG_SWIM
 };
 
-#define REQUEST_SENSE          0x03
-#define REQUEST_SENSE_LENGTH   18
+#define REQUEST_SENSE        0x03
+#define REQUEST_SENSE_LENGTH 18
+
+/*
+ * Map the relevant features, quirks and workaround for specific firmware
+ * version of stlink
+ */
+#define STLINK_F_HAS_TRACE              (1UL << 0)
+#define STLINK_F_HAS_SWD_SET_FREQ       (1UL << 1)
+#define STLINK_F_HAS_JTAG_SET_FREQ      (1UL << 2)
+#define STLINK_F_HAS_MEM_16BIT          (1UL << 3)
+
+/* aliases */
+#define STLINK_F_HAS_TARGET_VOLT        STLINK_F_HAS_TRACE
+
+struct speed_map {
+       int speed;
+       int speed_divisor;
+};
+
+/* SWD clock speed */
+static const struct speed_map stlink_khz_to_speed_map_swd[] = {
+       {4000, 0},
+       {1800, 1}, /* default */
+       {1200, 2},
+       {950,  3},
+       {480,  7},
+       {240, 15},
+       {125, 31},
+       {100, 40},
+       {50,  79},
+       {25, 158},
+       {15, 265},
+       {5,  798}
+};
+
+/* JTAG clock speed */
+static const struct speed_map stlink_khz_to_speed_map_jtag[] = {
+       {18000, 2},
+       {9000,  4},
+       {4500,  8},
+       {2250, 16},
+       {1125, 32}, /* default */
+       {562,  64},
+       {281, 128},
+       {140, 256}
+};
 
 static void stlink_usb_init_buffer(void *handle, uint8_t direction, uint32_t size);
+static int stlink_swim_status(void *handle);
 
 /** */
 static int stlink_usb_xfer_v1_get_status(void *handle)
 {
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
-
        /* read status */
        memset(h->cmdbuf, 0, STLINK_SG_SIZE);
 
-       if (jtag_libusb_bulk_read(h->fd, STLINK_RX_EP, (char *)h->cmdbuf,
-                               13, 1000) != 13)
+       if (jtag_libusb_bulk_read(h->fd, h->rx_ep, (char *)h->cmdbuf,
+                       13, STLINK_READ_TIMEOUT) != 13)
                return ERROR_FAIL;
 
        uint32_t t1;
@@ -208,26 +355,24 @@ static int stlink_usb_xfer_v1_get_status(void *handle)
 /** */
 static int stlink_usb_xfer_rw(void *handle, int cmdsize, const uint8_t *buf, int size)
 {
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
-
-       if (jtag_libusb_bulk_write(h->fd, STLINK_TX_EP, (char *)h->cmdbuf, cmdsize,
-                                  1000) != cmdsize) {
+       if (jtag_libusb_bulk_write(h->fd, h->tx_ep, (char *)h->cmdbuf, cmdsize,
+                       STLINK_WRITE_TIMEOUT) != cmdsize) {
                return ERROR_FAIL;
        }
 
-       if (h->direction == STLINK_TX_EP && size) {
-               if (jtag_libusb_bulk_write(h->fd, STLINK_TX_EP, (char *)buf,
-                                         size, 1000) != size) {
+       if (h->direction == h->tx_ep && size) {
+               if (jtag_libusb_bulk_write(h->fd, h->tx_ep, (char *)buf,
+                               size, STLINK_WRITE_TIMEOUT) != size) {
                        LOG_DEBUG("bulk write failed");
                        return ERROR_FAIL;
                }
-       } else if (h->direction == STLINK_RX_EP && size) {
-               if (jtag_libusb_bulk_read(h->fd, STLINK_RX_EP, (char *)buf,
-                                         size, 1000) != size) {
+       } else if (h->direction == h->rx_ep && size) {
+               if (jtag_libusb_bulk_read(h->fd, h->rx_ep, (char *)buf,
+                               size, STLINK_READ_TIMEOUT) != size) {
                        LOG_DEBUG("bulk read failed");
                        return ERROR_FAIL;
                }
@@ -240,13 +385,11 @@ static int stlink_usb_xfer_rw(void *handle, int cmdsize, const uint8_t *buf, int
 static int stlink_usb_xfer_v1_get_sense(void *handle)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
-
-       stlink_usb_init_buffer(handle, STLINK_RX_EP, 16);
+       stlink_usb_init_buffer(handle, h->rx_ep, 16);
 
        h->cmdbuf[h->cmdidx++] = REQUEST_SENSE;
        h->cmdbuf[h->cmdidx++] = 0;
@@ -265,18 +408,23 @@ static int stlink_usb_xfer_v1_get_sense(void *handle)
        return ERROR_OK;
 }
 
-/** */
+/*
+       transfers block in cmdbuf
+       <size> indicates number of bytes in the following
+       data phase.
+*/
 static int stlink_usb_xfer(void *handle, const uint8_t *buf, int size)
 {
        int err, cmdsize = STLINK_CMD_SIZE_V2;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
-
-       if (h->version.stlink == 1)
+       if (h->version.stlink == 1) {
                cmdsize = STLINK_SG_SIZE;
+               /* put length in bCBWCBLength */
+               h->cmdbuf[14] = h->cmdidx-15;
+       }
 
        err = stlink_usb_xfer_rw(handle, cmdsize, buf, size);
 
@@ -298,31 +446,177 @@ static int stlink_usb_xfer(void *handle, const uint8_t *buf, int size)
        return ERROR_OK;
 }
 
+/**
+    Converts an STLINK status code held in the first byte of a response
+    to an openocd error, logs any error/wait status as debug output.
+*/
+static int stlink_usb_error_check(void *handle)
+{
+       struct stlink_usb_handle_s *h = handle;
+
+       assert(handle != NULL);
+
+       if (h->transport == HL_TRANSPORT_SWIM) {
+               switch (h->databuf[0]) {
+                       case STLINK_SWIM_ERR_OK:
+                               return ERROR_OK;
+                       case STLINK_SWIM_BUSY:
+                               return ERROR_WAIT;
+                       default:
+                               LOG_DEBUG("unknown/unexpected STLINK status code 0x%x", h->databuf[0]);
+                               return ERROR_FAIL;
+               }
+       }
+
+       /* TODO: no error checking yet on api V1 */
+       if (h->version.jtag_api == STLINK_JTAG_API_V1)
+               h->databuf[0] = STLINK_DEBUG_ERR_OK;
+
+       switch (h->databuf[0]) {
+               case STLINK_DEBUG_ERR_OK:
+                       return ERROR_OK;
+               case STLINK_DEBUG_ERR_FAULT:
+                       LOG_DEBUG("SWD fault response (0x%x)", STLINK_DEBUG_ERR_FAULT);
+                       return ERROR_FAIL;
+               case STLINK_SWD_AP_WAIT:
+                       LOG_DEBUG("wait status SWD_AP_WAIT (0x%x)", STLINK_SWD_AP_WAIT);
+                       return ERROR_WAIT;
+               case STLINK_SWD_DP_WAIT:
+                       LOG_DEBUG("wait status SWD_DP_WAIT (0x%x)", STLINK_SWD_DP_WAIT);
+                       return ERROR_WAIT;
+               case STLINK_JTAG_WRITE_ERROR:
+                       LOG_DEBUG("Write error");
+                       return ERROR_FAIL;
+               case STLINK_JTAG_WRITE_VERIF_ERROR:
+                       LOG_DEBUG("Write verify error, ignoring");
+                       return ERROR_OK;
+               case STLINK_SWD_AP_FAULT:
+                       /* git://git.ac6.fr/openocd commit 657e3e885b9ee10
+                        * returns ERROR_OK with the comment:
+                        * Change in error status when reading outside RAM.
+                        * This fix allows CDT plugin to visualize memory.
+                        */
+                       LOG_DEBUG("STLINK_SWD_AP_FAULT");
+                       return ERROR_FAIL;
+               case STLINK_SWD_AP_ERROR:
+                       LOG_DEBUG("STLINK_SWD_AP_ERROR");
+                       return ERROR_FAIL;
+               case STLINK_SWD_AP_PARITY_ERROR:
+                       LOG_DEBUG("STLINK_SWD_AP_PARITY_ERROR");
+                       return ERROR_FAIL;
+               case STLINK_SWD_DP_FAULT:
+                       LOG_DEBUG("STLINK_SWD_DP_FAULT");
+                       return ERROR_FAIL;
+               case STLINK_SWD_DP_ERROR:
+                       LOG_DEBUG("STLINK_SWD_DP_ERROR");
+                       return ERROR_FAIL;
+               case STLINK_SWD_DP_PARITY_ERROR:
+                       LOG_DEBUG("STLINK_SWD_DP_PARITY_ERROR");
+                       return ERROR_FAIL;
+               case STLINK_SWD_AP_WDATA_ERROR:
+                       LOG_DEBUG("STLINK_SWD_AP_WDATA_ERROR");
+                       return ERROR_FAIL;
+               case STLINK_SWD_AP_STICKY_ERROR:
+                       LOG_DEBUG("STLINK_SWD_AP_STICKY_ERROR");
+                       return ERROR_FAIL;
+               case STLINK_SWD_AP_STICKYORUN_ERROR:
+                       LOG_DEBUG("STLINK_SWD_AP_STICKYORUN_ERROR");
+                       return ERROR_FAIL;
+               default:
+                       LOG_DEBUG("unknown/unexpected STLINK status code 0x%x", h->databuf[0]);
+                       return ERROR_FAIL;
+       }
+}
+
+
+/** Issue an STLINK command via USB transfer, with retries on any wait status responses.
+
+    Works for commands where the STLINK_DEBUG status is returned in the first
+    byte of the response packet. For SWIM a SWIM_READSTATUS is requested instead.
+
+    Returns an openocd result code.
+*/
+static int stlink_cmd_allow_retry(void *handle, const uint8_t *buf, int size)
+{
+       int retries = 0;
+       int res;
+       struct stlink_usb_handle_s *h = handle;
+
+       while (1) {
+               if ((h->transport != HL_TRANSPORT_SWIM) || !retries) {
+                       res = stlink_usb_xfer(handle, buf, size);
+                       if (res != ERROR_OK)
+                               return res;
+               }
+
+               if (h->transport == HL_TRANSPORT_SWIM) {
+                       res = stlink_swim_status(handle);
+                       if (res != ERROR_OK)
+                               return res;
+               }
+
+               res = stlink_usb_error_check(handle);
+               if (res == ERROR_WAIT && retries < MAX_WAIT_RETRIES) {
+                       usleep((1<<retries++) * 1000);
+                       continue;
+               }
+               return res;
+       }
+}
+
 /** */
-static void stlink_usb_xfer_v1_create_cmd(void *handle, uint8_t direction, uint32_t size)
+static int stlink_usb_read_trace(void *handle, const uint8_t *buf, int size)
 {
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
+
+       assert(handle != NULL);
+
+       assert(h->version.flags & STLINK_F_HAS_TRACE);
+
+       if (jtag_libusb_bulk_read(h->fd, h->trace_ep, (char *)buf,
+                       size, STLINK_READ_TIMEOUT) != size) {
+               LOG_ERROR("bulk trace read failed");
+               return ERROR_FAIL;
+       }
 
-       h = (struct stlink_usb_handle_s *)handle;
+       return ERROR_OK;
+}
+
+/*
+       this function writes transfer length in
+       the right place in the cb
+*/
+static void stlink_usb_set_cbw_transfer_datalength(void *handle, uint32_t size)
+{
+       struct stlink_usb_handle_s *h = handle;
+
+       buf_set_u32(h->cmdbuf+8, 0, 32, size);
+}
+
+static void stlink_usb_xfer_v1_create_cmd(void *handle, uint8_t direction, uint32_t size)
+{
+       struct stlink_usb_handle_s *h = handle;
 
        /* fill the send buffer */
        strcpy((char *)h->cmdbuf, "USBC");
        h->cmdidx += 4;
        /* csw tag not used */
+       buf_set_u32(h->cmdbuf+h->cmdidx, 0, 32, 0);
        h->cmdidx += 4;
+       /* cbw data transfer length (in the following data phase in or out) */
        buf_set_u32(h->cmdbuf+h->cmdidx, 0, 32, size);
        h->cmdidx += 4;
-       h->cmdbuf[h->cmdidx++] = (direction == STLINK_RX_EP ? ENDPOINT_IN : ENDPOINT_OUT);
+       /* cbw flags */
+       h->cmdbuf[h->cmdidx++] = (direction == h->rx_ep ? ENDPOINT_IN : ENDPOINT_OUT);
        h->cmdbuf[h->cmdidx++] = 0; /* lun */
-       h->cmdbuf[h->cmdidx++] = STLINK_CMD_SIZE_V1;
+       /* cdb clength (is filled in at xfer) */
+       h->cmdbuf[h->cmdidx++] = 0;
 }
 
 /** */
 static void stlink_usb_init_buffer(void *handle, uint8_t direction, uint32_t size)
 {
-       struct stlink_usb_handle_s *h;
-
-       h = (struct stlink_usb_handle_s *)handle;
+       struct stlink_usb_handle_s *h = handle;
 
        h->direction = direction;
 
@@ -335,54 +629,17 @@ static void stlink_usb_init_buffer(void *handle, uint8_t direction, uint32_t siz
                stlink_usb_xfer_v1_create_cmd(handle, direction, size);
 }
 
-static const char * const stlink_usb_error_msg[] = {
-       "unknown"
-};
-
-/** */
-static int stlink_usb_error_check(void *handle)
-{
-       int res;
-       const char *err_msg = 0;
-       struct stlink_usb_handle_s *h;
-
-       assert(handle != NULL);
-
-       h = (struct stlink_usb_handle_s *)handle;
-
-       /* TODO: no error checking yet on api V1 */
-       if (h->jtag_api == STLINK_JTAG_API_V1)
-               h->databuf[0] = STLINK_DEBUG_ERR_OK;
-
-       switch (h->databuf[0]) {
-               case STLINK_DEBUG_ERR_OK:
-                       res = ERROR_OK;
-                       break;
-               case STLINK_DEBUG_ERR_FAULT:
-               default:
-                       err_msg = stlink_usb_error_msg[0];
-                       res = ERROR_FAIL;
-                       break;
-       }
-
-       if (res != ERROR_OK)
-               LOG_DEBUG("status error: %d ('%s')", h->databuf[0], err_msg);
-
-       return res;
-}
-
 /** */
 static int stlink_usb_version(void *handle)
 {
        int res;
+       uint32_t flags;
        uint16_t v;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
-
-       stlink_usb_init_buffer(handle, STLINK_RX_EP, 6);
+       stlink_usb_init_buffer(handle, h->rx_ep, 6);
 
        h->cmdbuf[h->cmdidx++] = STLINK_GET_VERSION;
 
@@ -399,18 +656,47 @@ static int stlink_usb_version(void *handle)
        h->vid = buf_get_u32(h->databuf, 16, 16);
        h->pid = buf_get_u32(h->databuf, 32, 16);
 
-       /* set the supported jtag api version
-        * API V2 is supported since JTAG V11
-        */
-       if (h->version.jtag >= 11)
-               h->version.jtag_api_max = STLINK_JTAG_API_V2;
-       else
-               h->version.jtag_api_max = STLINK_JTAG_API_V1;
+       flags = 0;
+       switch (h->version.stlink) {
+       case 1:
+               /* ST-LINK/V1 from J11 switch to api-v2 (and support SWD) */
+               if (h->version.jtag >= 11)
+                       h->version.jtag_api = STLINK_JTAG_API_V2;
+               else
+                       h->version.jtag_api = STLINK_JTAG_API_V1;
+
+               break;
+       case 2:
+               /* all ST-LINK/V2 and ST-Link/V2.1 use api-v2 */
+               h->version.jtag_api = STLINK_JTAG_API_V2;
+
+               /* API for trace from J13 */
+               /* API for target voltage from J13 */
+               if (h->version.jtag >= 13)
+                       flags |= STLINK_F_HAS_TRACE;
+
+               /* API to set SWD frequency from J22 */
+               if (h->version.jtag >= 22)
+                       flags |= STLINK_F_HAS_SWD_SET_FREQ;
+
+               /* API to set JTAG frequency from J24 */
+               if (h->version.jtag >= 24)
+                       flags |= STLINK_F_HAS_JTAG_SET_FREQ;
+
+               /* API to read/write memory at 16 bit from J26 */
+               if (h->version.jtag >= 26)
+                       flags |= STLINK_F_HAS_MEM_16BIT;
+
+               break;
+       default:
+               break;
+       }
+       h->version.flags = flags;
 
-       LOG_DEBUG("STLINK v%d JTAG v%d API v%d SWIM v%d VID 0x%04X PID 0x%04X",
+       LOG_INFO("STLINK v%d JTAG v%d API v%d SWIM v%d VID 0x%04X PID 0x%04X",
                h->version.stlink,
                h->version.jtag,
-               (h->version.jtag_api_max == STLINK_JTAG_API_V1) ? 1 : 2,
+               (h->version.jtag_api == STLINK_JTAG_API_V1) ? 1 : 2,
                h->version.swim,
                h->vid,
                h->pid);
@@ -418,17 +704,95 @@ static int stlink_usb_version(void *handle)
        return ERROR_OK;
 }
 
+static int stlink_usb_check_voltage(void *handle, float *target_voltage)
+{
+       struct stlink_usb_handle_s *h = handle;
+       uint32_t adc_results[2];
+
+       /* no error message, simply quit with error */
+       if (!(h->version.flags & STLINK_F_HAS_TARGET_VOLT))
+               return ERROR_COMMAND_NOTFOUND;
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 8);
+
+       h->cmdbuf[h->cmdidx++] = STLINK_GET_TARGET_VOLTAGE;
+
+       int result = stlink_usb_xfer(handle, h->databuf, 8);
+
+       if (result != ERROR_OK)
+               return result;
+
+       /* convert result */
+       adc_results[0] = le_to_h_u32(h->databuf);
+       adc_results[1] = le_to_h_u32(h->databuf + 4);
+
+       *target_voltage = 0;
+
+       if (adc_results[0])
+               *target_voltage = 2 * ((float)adc_results[1]) * (float)(1.2 / adc_results[0]);
+
+       LOG_INFO("Target voltage: %f", (double)*target_voltage);
+
+       return ERROR_OK;
+}
+
+static int stlink_usb_set_swdclk(void *handle, uint16_t clk_divisor)
+{
+       struct stlink_usb_handle_s *h = handle;
+
+       assert(handle != NULL);
+
+       if (!(h->version.flags & STLINK_F_HAS_SWD_SET_FREQ))
+               return ERROR_COMMAND_NOTFOUND;
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
+
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_SWD_SET_FREQ;
+       h_u16_to_le(h->cmdbuf+h->cmdidx, clk_divisor);
+       h->cmdidx += 2;
+
+       int result = stlink_cmd_allow_retry(handle, h->databuf, 2);
+
+       if (result != ERROR_OK)
+               return result;
+
+       return ERROR_OK;
+}
+
+static int stlink_usb_set_jtagclk(void *handle, uint16_t clk_divisor)
+{
+       struct stlink_usb_handle_s *h = handle;
+
+       assert(handle != NULL);
+
+       if (!(h->version.flags & STLINK_F_HAS_JTAG_SET_FREQ))
+               return ERROR_COMMAND_NOTFOUND;
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
+
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_JTAG_SET_FREQ;
+       h_u16_to_le(h->cmdbuf+h->cmdidx, clk_divisor);
+       h->cmdidx += 2;
+
+       int result = stlink_cmd_allow_retry(handle, h->databuf, 2);
+
+       if (result != ERROR_OK)
+               return result;
+
+       return ERROR_OK;
+}
+
 /** */
 static int stlink_usb_current_mode(void *handle, uint8_t *mode)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
-
-       stlink_usb_init_buffer(handle, STLINK_RX_EP, 2);
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
 
        h->cmdbuf[h->cmdidx++] = STLINK_GET_CURRENT_MODE;
 
@@ -445,43 +809,42 @@ static int stlink_usb_current_mode(void *handle, uint8_t *mode)
 /** */
 static int stlink_usb_mode_enter(void *handle, enum stlink_mode type)
 {
-       int res;
        int rx_size = 0;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
-
        /* on api V2 we are able the read the latest command
         * status
         * TODO: we need the test on api V1 too
         */
-       if (h->jtag_api == STLINK_JTAG_API_V2)
+       if (h->version.jtag_api == STLINK_JTAG_API_V2)
                rx_size = 2;
 
-       stlink_usb_init_buffer(handle, STLINK_RX_EP, rx_size);
+       stlink_usb_init_buffer(handle, h->rx_ep, rx_size);
 
        switch (type) {
                case STLINK_MODE_DEBUG_JTAG:
                        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
-                       if (h->jtag_api == STLINK_JTAG_API_V1)
+                       if (h->version.jtag_api == STLINK_JTAG_API_V1)
                                h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV1_ENTER;
                        else
                                h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_ENTER;
-                       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_ENTER_JTAG;
+                       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_ENTER_JTAG_NO_RESET;
                        break;
                case STLINK_MODE_DEBUG_SWD:
                        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
-                       if (h->jtag_api == STLINK_JTAG_API_V1)
+                       if (h->version.jtag_api == STLINK_JTAG_API_V1)
                                h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV1_ENTER;
                        else
                                h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_ENTER;
-                       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_ENTER_SWD;
+                       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_ENTER_SWD_NO_RESET;
                        break;
                case STLINK_MODE_DEBUG_SWIM:
                        h->cmdbuf[h->cmdidx++] = STLINK_SWIM_COMMAND;
                        h->cmdbuf[h->cmdidx++] = STLINK_SWIM_ENTER;
+                       /* no answer for this function... */
+                       rx_size = 0;
                        break;
                case STLINK_MODE_DFU:
                case STLINK_MODE_MASS:
@@ -489,26 +852,17 @@ static int stlink_usb_mode_enter(void *handle, enum stlink_mode type)
                        return ERROR_FAIL;
        }
 
-       res = stlink_usb_xfer(handle, h->databuf, rx_size);
-
-       if (res != ERROR_OK)
-               return res;
-
-       res = stlink_usb_error_check(h);
-
-       return res;
+       return stlink_cmd_allow_retry(handle, h->databuf, rx_size);
 }
 
 /** */
 static int stlink_usb_mode_leave(void *handle, enum stlink_mode type)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
-
        stlink_usb_init_buffer(handle, STLINK_NULL_EP, 0);
 
        switch (type) {
@@ -538,18 +892,32 @@ static int stlink_usb_mode_leave(void *handle, enum stlink_mode type)
        return ERROR_OK;
 }
 
+static int stlink_usb_assert_srst(void *handle, int srst);
+
+static enum stlink_mode stlink_get_mode(enum hl_transports t)
+{
+       switch (t) {
+       case HL_TRANSPORT_SWD:
+               return STLINK_MODE_DEBUG_SWD;
+       case HL_TRANSPORT_JTAG:
+               return STLINK_MODE_DEBUG_JTAG;
+       case HL_TRANSPORT_SWIM:
+               return STLINK_MODE_DEBUG_SWIM;
+       default:
+               return STLINK_MODE_UNKNOWN;
+       }
+}
+
 /** */
-static int stlink_usb_init_mode(void *handle)
+static int stlink_usb_init_mode(void *handle, bool connect_under_reset)
 {
        int res;
        uint8_t mode;
        enum stlink_mode emode;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
-
        res = stlink_usb_current_mode(handle, &mode);
 
        if (res != ERROR_OK)
@@ -587,34 +955,62 @@ static int stlink_usb_init_mode(void *handle)
        if (res != ERROR_OK)
                return res;
 
+       /* we check the target voltage here as an aid to debugging connection problems.
+        * the stlink requires the target Vdd to be connected for reliable debugging.
+        * this cmd is supported in all modes except DFU
+        */
+       if (mode != STLINK_DEV_DFU_MODE) {
+
+               float target_voltage;
+
+               /* check target voltage (if supported) */
+               res = stlink_usb_check_voltage(h, &target_voltage);
+
+               if (res != ERROR_OK) {
+                       if (res != ERROR_COMMAND_NOTFOUND)
+                               LOG_ERROR("voltage check failed");
+                       /* attempt to continue as it is not a catastrophic failure */
+               } else {
+                       /* check for a sensible target voltage, operating range is 1.65-5.5v
+                        * according to datasheet */
+                       if (target_voltage < 1.5)
+                               LOG_ERROR("target voltage may be too low for reliable debugging");
+               }
+       }
+
        LOG_DEBUG("MODE: 0x%02X", mode);
 
        /* set selected mode */
-       switch (h->transport) {
-               case STLINK_TRANSPORT_SWD:
-                       emode = STLINK_MODE_DEBUG_SWD;
-                       break;
-               case STLINK_TRANSPORT_JTAG:
-                       emode = STLINK_MODE_DEBUG_JTAG;
-                       break;
-               case STLINK_TRANSPORT_SWIM:
-                       emode = STLINK_MODE_DEBUG_SWIM;
-                       break;
-               default:
-                       emode = STLINK_MODE_UNKNOWN;
-                       break;
-       }
+       emode = stlink_get_mode(h->transport);
 
        if (emode == STLINK_MODE_UNKNOWN) {
                LOG_ERROR("selected mode (transport) not supported");
                return ERROR_FAIL;
        }
 
-       res = stlink_usb_mode_enter(handle, emode);
+       /* preliminary SRST assert:
+        * We want SRST is asserted before activating debug signals (mode_enter).
+        * As the required mode has not been set, the adapter may not know what pin to use.
+        * Tested firmware STLINK v2 JTAG v29 API v2 SWIM v0 uses T_NRST pin by default
+        * Tested firmware STLINK v2 JTAG v27 API v2 SWIM v6 uses T_NRST pin by default
+        * after power on, SWIM_RST stays unchanged */
+       if (connect_under_reset && emode != STLINK_MODE_DEBUG_SWIM)
+               stlink_usb_assert_srst(handle, 0);
+               /* do not check the return status here, we will
+                  proceed and enter the desired mode below
+                  and try asserting srst again. */
 
+       res = stlink_usb_mode_enter(handle, emode);
        if (res != ERROR_OK)
                return res;
 
+       /* assert SRST again: a little bit late but now the adapter knows for sure what pin to use */
+       if (connect_under_reset) {
+               res = stlink_usb_assert_srst(handle, 0);
+               if (res != ERROR_OK)
+                       return res;
+       }
+
        res = stlink_usb_current_mode(handle, &mode);
 
        if (res != ERROR_OK)
@@ -625,72 +1021,262 @@ static int stlink_usb_init_mode(void *handle)
        return ERROR_OK;
 }
 
-/** */
-static int stlink_usb_idcode(void *handle, uint32_t *idcode)
+/* request status from last swim request */
+static int stlink_swim_status(void *handle)
 {
+       struct stlink_usb_handle_s *h = handle;
        int res;
-       struct stlink_usb_handle_s *h;
-
-       assert(handle != NULL);
-
-       h = (struct stlink_usb_handle_s *)handle;
-
-       stlink_usb_init_buffer(handle, STLINK_RX_EP, 4);
-
-       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
-       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_READCOREID;
 
+       stlink_usb_init_buffer(handle, h->rx_ep, 4);
+       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_READSTATUS;
        res = stlink_usb_xfer(handle, h->databuf, 4);
-
        if (res != ERROR_OK)
                return res;
-
-       *idcode = le_to_h_u32(h->databuf);
-
-       LOG_DEBUG("IDCODE: 0x%08X", *idcode);
-
        return ERROR_OK;
 }
-
-static int stlink_usb_v2_read_debug_reg(void *handle, uint32_t addr, uint32_t *val)
+/*
+       the purpose of this function is unknown...
+       capabilites? anyway for swim v6 it returns
+       0001020600000000
+*/
+__attribute__((unused))
+static int stlink_swim_cap(void *handle, uint8_t *cap)
 {
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
        int res;
 
-       assert(handle != NULL);
-
-       h = (struct stlink_usb_handle_s *)handle;
-
-       stlink_usb_init_buffer(handle, STLINK_RX_EP, 8);
-
-       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
-       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_READDEBUGREG;
-       h_u32_to_le(h->cmdbuf+h->cmdidx, addr);
-       h->cmdidx += 4;
-
+       stlink_usb_init_buffer(handle, h->rx_ep, 8);
+       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_READ_CAP;
+       h->cmdbuf[h->cmdidx++] = 0x01;
        res = stlink_usb_xfer(handle, h->databuf, 8);
-
        if (res != ERROR_OK)
                return res;
+       memcpy(cap, h->databuf, 8);
+       return ERROR_OK;
+}
 
-       *val = le_to_h_u32(h->databuf + 4);
+/*     debug dongle assert/deassert sreset line */
+static int stlink_swim_assert_reset(void *handle, int reset)
+{
+       struct stlink_usb_handle_s *h = handle;
+       int res;
 
-       return h->databuf[0] == STLINK_DEBUG_ERR_OK ? ERROR_OK : ERROR_FAIL;
+       stlink_usb_init_buffer(handle, h->rx_ep, 0);
+       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_COMMAND;
+       if (!reset)
+               h->cmdbuf[h->cmdidx++] = STLINK_SWIM_ASSERT_RESET;
+       else
+               h->cmdbuf[h->cmdidx++] = STLINK_SWIM_DEASSERT_RESET;
+       res = stlink_cmd_allow_retry(handle, h->databuf, 0);
+       if (res != ERROR_OK)
+               return res;
+       return ERROR_OK;
 }
 
-static int stlink_usb_write_debug_reg(void *handle, uint32_t addr, uint32_t val)
+/*
+       send swim enter seq
+       1.3ms low then 750Hz then 1.5kHz
+*/
+static int stlink_swim_enter(void *handle)
 {
+       struct stlink_usb_handle_s *h = handle;
+       int res;
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 0);
+       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_ENTER_SEQ;
+       res = stlink_cmd_allow_retry(handle, h->databuf, 0);
+       if (res != ERROR_OK)
+               return res;
+       return ERROR_OK;
+}
+
+/*     switch high/low speed swim */
+static int stlink_swim_speed(void *handle, int speed)
+{
+       struct stlink_usb_handle_s *h = handle;
+       int res;
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 0);
+       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_SPEED;
+       if (speed)
+               h->cmdbuf[h->cmdidx++] = 1;
+       else
+               h->cmdbuf[h->cmdidx++] = 0;
+       res = stlink_cmd_allow_retry(handle, h->databuf, 0);
+       if (res != ERROR_OK)
+               return res;
+       return ERROR_OK;
+}
+
+/*
+       initiate srst from swim.
+       nrst is pulled low for 50us.
+*/
+static int stlink_swim_generate_rst(void *handle)
+{
+       struct stlink_usb_handle_s *h = handle;
+       int res;
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 0);
+       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_GEN_RST;
+       res = stlink_cmd_allow_retry(handle, h->databuf, 0);
+       if (res != ERROR_OK)
+               return res;
+       return ERROR_OK;
+}
+
+/*
+       send resyncronize sequence
+       swim is pulled low for 16us
+       reply is 64 clks low
+*/
+static int stlink_swim_resync(void *handle)
+{
+       struct stlink_usb_handle_s *h = handle;
+       int res;
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 0);
+       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_RESET;
+       res = stlink_cmd_allow_retry(handle, h->databuf, 0);
+       if (res != ERROR_OK)
+               return res;
+       return ERROR_OK;
+}
+
+static int stlink_swim_writebytes(void *handle, uint32_t addr, uint32_t len, const uint8_t *data)
+{
+       struct stlink_usb_handle_s *h = handle;
+       int res;
+       unsigned int i;
+       unsigned int datalen = 0;
+       int cmdsize = STLINK_CMD_SIZE_V2;
+
+       if (len > STLINK_DATA_SIZE)
+               return ERROR_FAIL;
+
+       if (h->version.stlink == 1)
+               cmdsize = STLINK_SG_SIZE;
+
+       stlink_usb_init_buffer(handle, h->tx_ep, 0);
+       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_WRITEMEM;
+       h_u16_to_be(h->cmdbuf+h->cmdidx, len);
+       h->cmdidx += 2;
+       h_u32_to_be(h->cmdbuf+h->cmdidx, addr);
+       h->cmdidx += 4;
+       for (i = 0; i < len; i++) {
+               if (h->cmdidx == cmdsize)
+                       h->databuf[datalen++] = *(data++);
+               else
+                       h->cmdbuf[h->cmdidx++] = *(data++);
+       }
+       if (h->version.stlink == 1)
+               stlink_usb_set_cbw_transfer_datalength(handle, datalen);
+
+       res = stlink_cmd_allow_retry(handle, h->databuf, datalen);
+       if (res != ERROR_OK)
+               return res;
+       return ERROR_OK;
+}
+
+static int stlink_swim_readbytes(void *handle, uint32_t addr, uint32_t len, uint8_t *data)
+{
+       struct stlink_usb_handle_s *h = handle;
+       int res;
+
+       if (len > STLINK_DATA_SIZE)
+               return ERROR_FAIL;
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 0);
+       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_READMEM;
+       h_u16_to_be(h->cmdbuf+h->cmdidx, len);
+       h->cmdidx += 2;
+       h_u32_to_be(h->cmdbuf+h->cmdidx, addr);
+       h->cmdidx += 4;
+       res = stlink_cmd_allow_retry(handle, h->databuf, 0);
+       if (res != ERROR_OK)
+               return res;
+
+       stlink_usb_init_buffer(handle, h->rx_ep, len);
+       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_SWIM_READBUF;
+       res = stlink_usb_xfer(handle, data, len);
+       if (res != ERROR_OK)
+               return res;
+
+       return ERROR_OK;
+}
+
+/** */
+static int stlink_usb_idcode(void *handle, uint32_t *idcode)
+{
+       int res;
+       struct stlink_usb_handle_s *h = handle;
+
+       assert(handle != NULL);
+
+       /* there is no swim read core id cmd */
+       if (h->transport == HL_TRANSPORT_SWIM) {
+               *idcode = 0;
+               return ERROR_OK;
+       }
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 4);
+
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_READCOREID;
+
+       res = stlink_usb_xfer(handle, h->databuf, 4);
+
+       if (res != ERROR_OK)
+               return res;
+
+       *idcode = le_to_h_u32(h->databuf);
+
+       LOG_DEBUG("IDCODE: 0x%08" PRIX32, *idcode);
+
+       return ERROR_OK;
+}
+
+static int stlink_usb_v2_read_debug_reg(void *handle, uint32_t addr, uint32_t *val)
+{
+       struct stlink_usb_handle_s *h = handle;
        int res;
-       struct stlink_usb_handle_s *h;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       stlink_usb_init_buffer(handle, h->rx_ep, 8);
 
-       stlink_usb_init_buffer(handle, STLINK_RX_EP, 2);
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_READDEBUGREG;
+       h_u32_to_le(h->cmdbuf+h->cmdidx, addr);
+       h->cmdidx += 4;
+
+       res = stlink_cmd_allow_retry(handle, h->databuf, 8);
+       if (res != ERROR_OK)
+               return res;
+
+       *val = le_to_h_u32(h->databuf + 4);
+       return ERROR_OK;
+}
+
+static int stlink_usb_write_debug_reg(void *handle, uint32_t addr, uint32_t val)
+{
+       struct stlink_usb_handle_s *h = handle;
+
+       assert(handle != NULL);
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
 
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
-       if (h->jtag_api == STLINK_JTAG_API_V1)
+       if (h->version.jtag_api == STLINK_JTAG_API_V1)
                h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV1_WRITEDEBUGREG;
        else
                h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_WRITEDEBUGREG;
@@ -699,12 +1285,40 @@ static int stlink_usb_write_debug_reg(void *handle, uint32_t addr, uint32_t val)
        h_u32_to_le(h->cmdbuf+h->cmdidx, val);
        h->cmdidx += 4;
 
-       res = stlink_usb_xfer(handle, h->databuf, 2);
+       return stlink_cmd_allow_retry(handle, h->databuf, 2);
+}
 
-       if (res != ERROR_OK)
-               return res;
+/** */
+static int stlink_usb_trace_read(void *handle, uint8_t *buf, size_t *size)
+{
+       struct stlink_usb_handle_s *h = handle;
 
-       return h->databuf[0] == STLINK_DEBUG_ERR_OK ? ERROR_OK : ERROR_FAIL;
+       assert(handle != NULL);
+
+       if (h->trace.enabled && (h->version.flags & STLINK_F_HAS_TRACE)) {
+               int res;
+
+               stlink_usb_init_buffer(handle, h->rx_ep, 10);
+
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_GET_TRACE_NB;
+
+               res = stlink_usb_xfer(handle, h->databuf, 2);
+               if (res != ERROR_OK)
+                       return res;
+
+               size_t bytes_avail = le_to_h_u16(h->databuf);
+               *size = bytes_avail < *size ? bytes_avail : *size - 1;
+
+               if (*size > 0) {
+                       res = stlink_usb_read_trace(handle, buf, *size);
+                       if (res != ERROR_OK)
+                               return res;
+                       return ERROR_OK;
+               }
+       }
+       *size = 0;
+       return ERROR_OK;
 }
 
 static enum target_state stlink_usb_v2_get_status(void *handle)
@@ -728,16 +1342,40 @@ static enum target_state stlink_usb_v2_get_status(void *handle)
 static enum target_state stlink_usb_state(void *handle)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       if (h->transport == HL_TRANSPORT_SWIM) {
+               res = stlink_usb_mode_enter(handle, stlink_get_mode(h->transport));
+               if (res != ERROR_OK)
+                       return TARGET_UNKNOWN;
 
-       if (h->jtag_api == STLINK_JTAG_API_V2)
-               return stlink_usb_v2_get_status(handle);
+               res = stlink_swim_resync(handle);
+               if (res != ERROR_OK)
+                       return TARGET_UNKNOWN;
 
-       stlink_usb_init_buffer(handle, STLINK_RX_EP, 2);
+               return ERROR_OK;
+       }
+
+       if (h->reconnect_pending) {
+               LOG_INFO("Previous state query failed, trying to reconnect");
+               res = stlink_usb_mode_enter(handle, stlink_get_mode(h->transport));
+
+               if (res != ERROR_OK)
+                       return TARGET_UNKNOWN;
+
+               h->reconnect_pending = false;
+       }
+
+       if (h->version.jtag_api == STLINK_JTAG_API_V2) {
+               res = stlink_usb_v2_get_status(handle);
+               if (res == TARGET_UNKNOWN)
+                       h->reconnect_pending = true;
+               return res;
+       }
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
 
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_GETSTATUS;
@@ -752,161 +1390,197 @@ static enum target_state stlink_usb_state(void *handle)
        if (h->databuf[0] == STLINK_CORE_HALTED)
                return TARGET_HALTED;
 
+       h->reconnect_pending = true;
+
        return TARGET_UNKNOWN;
 }
 
-/** */
-static int stlink_usb_reset(void *handle)
+static int stlink_usb_assert_srst(void *handle, int srst)
 {
-       int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       if (h->transport == HL_TRANSPORT_SWIM)
+               return stlink_swim_assert_reset(handle, srst);
+
+       if (h->version.stlink == 1)
+               return ERROR_COMMAND_NOTFOUND;
 
-       stlink_usb_init_buffer(handle, STLINK_RX_EP, 2);
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
 
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_DRIVE_NRST;
+       h->cmdbuf[h->cmdidx++] = srst;
 
-       if (h->jtag_api == STLINK_JTAG_API_V1)
-               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV1_RESETSYS;
-       else
-               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_RESETSYS;
+       return stlink_cmd_allow_retry(handle, h->databuf, 2);
+}
 
-       res = stlink_usb_xfer(handle, h->databuf, 2);
+/** */
+static void stlink_usb_trace_disable(void *handle)
+{
+       int res = ERROR_OK;
+       struct stlink_usb_handle_s *h = handle;
 
-       if (res != ERROR_OK)
-               return res;
+       assert(handle != NULL);
+
+       assert(h->version.flags & STLINK_F_HAS_TRACE);
 
-       LOG_DEBUG("RESET: 0x%08X", h->databuf[0]);
+       LOG_DEBUG("Tracing: disable");
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_STOP_TRACE_RX;
+       res = stlink_usb_xfer(handle, h->databuf, 2);
 
-       return h->databuf[0] == STLINK_DEBUG_ERR_OK ? ERROR_OK : ERROR_FAIL;
+       if (res == ERROR_OK)
+               h->trace.enabled = false;
 }
 
-static int stlink_usb_assert_srst(void *handle, int srst)
+
+/** */
+static int stlink_usb_trace_enable(void *handle)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       if (h->version.flags & STLINK_F_HAS_TRACE) {
+               stlink_usb_init_buffer(handle, h->rx_ep, 10);
 
-       if (h->jtag_api == STLINK_JTAG_API_V1)
-               return ERROR_COMMAND_NOTFOUND;
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_START_TRACE_RX;
+               h_u16_to_le(h->cmdbuf+h->cmdidx, (uint16_t)STLINK_TRACE_SIZE);
+               h->cmdidx += 2;
+               h_u32_to_le(h->cmdbuf+h->cmdidx, h->trace.source_hz);
+               h->cmdidx += 4;
+
+               res = stlink_usb_xfer(handle, h->databuf, 2);
+
+               if (res == ERROR_OK)  {
+                       h->trace.enabled = true;
+                       LOG_DEBUG("Tracing: recording at %" PRIu32 "Hz", h->trace.source_hz);
+               }
+       } else {
+               LOG_ERROR("Tracing is not supported by this version.");
+               res = ERROR_FAIL;
+       }
+
+       return res;
+}
 
-       stlink_usb_init_buffer(handle, STLINK_RX_EP, 2);
+/** */
+static int stlink_usb_reset(void *handle)
+{
+       struct stlink_usb_handle_s *h = handle;
+       int retval;
+
+       assert(handle != NULL);
+
+       if (h->transport == HL_TRANSPORT_SWIM)
+               return stlink_swim_generate_rst(handle);
+
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
 
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
-       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_DRIVE_NRST;
-       h->cmdbuf[h->cmdidx++] = srst;
 
-       res = stlink_usb_xfer(handle, h->databuf, 2);
+       if (h->version.jtag_api == STLINK_JTAG_API_V1)
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV1_RESETSYS;
+       else
+               h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_RESETSYS;
 
-       if (res != ERROR_OK)
-               return res;
+       retval = stlink_cmd_allow_retry(handle, h->databuf, 2);
+       if (retval != ERROR_OK)
+               return retval;
+
+       if (h->trace.enabled) {
+               stlink_usb_trace_disable(h);
+               return stlink_usb_trace_enable(h);
+       }
 
-       return h->databuf[0] == STLINK_DEBUG_ERR_OK ? ERROR_OK : ERROR_FAIL;
+       return ERROR_OK;
 }
 
 /** */
 static int stlink_usb_run(void *handle)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       if (h->version.jtag_api == STLINK_JTAG_API_V2) {
+               res = stlink_usb_write_debug_reg(handle, DCB_DHCSR, DBGKEY|C_DEBUGEN);
 
-       if (h->jtag_api == STLINK_JTAG_API_V2)
-               return stlink_usb_write_debug_reg(handle, DCB_DHCSR, DBGKEY|C_DEBUGEN);
+               return res;
+       }
 
-       stlink_usb_init_buffer(handle, STLINK_RX_EP, 2);
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
 
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_RUNCORE;
 
-       res = stlink_usb_xfer(handle, h->databuf, 2);
-
-       if (res != ERROR_OK)
-               return res;
-
-       return h->databuf[0] == STLINK_DEBUG_ERR_OK ? ERROR_OK : ERROR_FAIL;
+       return stlink_cmd_allow_retry(handle, h->databuf, 2);
 }
 
 /** */
 static int stlink_usb_halt(void *handle)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       if (h->version.jtag_api == STLINK_JTAG_API_V2) {
+               res = stlink_usb_write_debug_reg(handle, DCB_DHCSR, DBGKEY|C_HALT|C_DEBUGEN);
 
-       if (h->jtag_api == STLINK_JTAG_API_V2)
-               return stlink_usb_write_debug_reg(handle, DCB_DHCSR, DBGKEY|C_HALT|C_DEBUGEN);
+               return res;
+       }
 
-       stlink_usb_init_buffer(handle, STLINK_RX_EP, 2);
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
 
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_FORCEDEBUG;
 
-       res = stlink_usb_xfer(handle, h->databuf, 2);
-
-       if (res != ERROR_OK)
-               return res;
-
-       return h->databuf[0] == STLINK_DEBUG_ERR_OK ? ERROR_OK : ERROR_FAIL;
+       return stlink_cmd_allow_retry(handle, h->databuf, 2);
 }
 
 /** */
 static int stlink_usb_step(void *handle)
 {
-       int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
-
-       if (h->jtag_api == STLINK_JTAG_API_V2) {
+       if (h->version.jtag_api == STLINK_JTAG_API_V2) {
                /* TODO: this emulates the v1 api, it should really use a similar auto mask isr
-                * that the cortex-m3 currently does. */
+                * that the Cortex-M3 currently does. */
                stlink_usb_write_debug_reg(handle, DCB_DHCSR, DBGKEY|C_HALT|C_MASKINTS|C_DEBUGEN);
                stlink_usb_write_debug_reg(handle, DCB_DHCSR, DBGKEY|C_STEP|C_MASKINTS|C_DEBUGEN);
                return stlink_usb_write_debug_reg(handle, DCB_DHCSR, DBGKEY|C_HALT|C_DEBUGEN);
        }
 
-       stlink_usb_init_buffer(handle, STLINK_RX_EP, 2);
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
 
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_STEPCORE;
 
-       res = stlink_usb_xfer(handle, h->databuf, 2);
-
-       if (res != ERROR_OK)
-               return res;
-
-       return h->databuf[0] == STLINK_DEBUG_ERR_OK ? ERROR_OK : ERROR_FAIL;
+       return stlink_cmd_allow_retry(handle, h->databuf, 2);
 }
 
 /** */
 static int stlink_usb_read_regs(void *handle)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
-
-       stlink_usb_init_buffer(handle, STLINK_RX_EP, 84);
+       stlink_usb_init_buffer(handle, h->rx_ep, 84);
 
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
-       if (h->jtag_api == STLINK_JTAG_API_V1)
+       if (h->version.jtag_api == STLINK_JTAG_API_V1)
                h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV1_READALLREGS;
        else
                h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_READALLREGS;
@@ -923,50 +1597,45 @@ static int stlink_usb_read_regs(void *handle)
 static int stlink_usb_read_reg(void *handle, int num, uint32_t *val)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
-
-       stlink_usb_init_buffer(handle, STLINK_RX_EP, h->jtag_api == STLINK_JTAG_API_V1 ? 4 : 8);
+       stlink_usb_init_buffer(handle, h->rx_ep, h->version.jtag_api == STLINK_JTAG_API_V1 ? 4 : 8);
 
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
-       if (h->jtag_api == STLINK_JTAG_API_V1)
+       if (h->version.jtag_api == STLINK_JTAG_API_V1)
                h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV1_READREG;
        else
                h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_READREG;
        h->cmdbuf[h->cmdidx++] = num;
 
-       res = stlink_usb_xfer(handle, h->databuf, h->jtag_api == STLINK_JTAG_API_V1 ? 4 : 8);
-
-       if (res != ERROR_OK)
-               return res;
-
-       if (h->jtag_api == STLINK_JTAG_API_V1)
+       if (h->version.jtag_api == STLINK_JTAG_API_V1) {
+               res = stlink_usb_xfer(handle, h->databuf, 4);
+               if (res != ERROR_OK)
+                       return res;
                *val = le_to_h_u32(h->databuf);
-       else {
+               return ERROR_OK;
+       } else {
+               res = stlink_cmd_allow_retry(handle, h->databuf, 8);
+               if (res != ERROR_OK)
+                       return res;
                *val = le_to_h_u32(h->databuf + 4);
-               return h->databuf[0] == STLINK_DEBUG_ERR_OK ? ERROR_OK : ERROR_FAIL;
+               return ERROR_OK;
        }
-
-       return ERROR_OK;
 }
 
 /** */
 static int stlink_usb_write_reg(void *handle, int num, uint32_t val)
 {
-       int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
-
-       stlink_usb_init_buffer(handle, STLINK_RX_EP, 2);
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
 
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
-       if (h->jtag_api == STLINK_JTAG_API_V1)
+       if (h->version.jtag_api == STLINK_JTAG_API_V1)
                h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV1_WRITEREG;
        else
                h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_WRITEREG;
@@ -974,27 +1643,20 @@ static int stlink_usb_write_reg(void *handle, int num, uint32_t val)
        h_u32_to_le(h->cmdbuf+h->cmdidx, val);
        h->cmdidx += 4;
 
-       res = stlink_usb_xfer(handle, h->databuf, 2);
-
-       if (res != ERROR_OK)
-               return res;
-
-       return h->databuf[0] == STLINK_DEBUG_ERR_OK ? ERROR_OK : ERROR_FAIL;
+       return stlink_cmd_allow_retry(handle, h->databuf, 2);
 }
 
 static int stlink_usb_get_rw_status(void *handle)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
-
-       if (h->jtag_api == STLINK_JTAG_API_V1)
+       if (h->version.jtag_api == STLINK_JTAG_API_V1)
                return ERROR_OK;
 
-       stlink_usb_init_buffer(handle, STLINK_RX_EP, 2);
+       stlink_usb_init_buffer(handle, h->rx_ep, 2);
 
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_GETLASTRWSTATUS;
@@ -1004,7 +1666,7 @@ static int stlink_usb_get_rw_status(void *handle)
        if (res != ERROR_OK)
                return res;
 
-       return h->databuf[0] == STLINK_DEBUG_ERR_OK ? ERROR_OK : res;
+       return stlink_usb_error_check(h);
 }
 
 /** */
@@ -1013,13 +1675,17 @@ static int stlink_usb_read_mem8(void *handle, uint32_t addr, uint16_t len,
 {
        int res;
        uint16_t read_len = len;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       /* max 8bit read/write is 64bytes */
+       if (len > STLINK_MAX_RW8) {
+               LOG_DEBUG("max buffer length exceeded");
+               return ERROR_FAIL;
+       }
 
-       stlink_usb_init_buffer(handle, STLINK_RX_EP, read_len);
+       stlink_usb_init_buffer(handle, h->rx_ep, read_len);
 
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_READMEM_8BIT;
@@ -1047,13 +1713,17 @@ static int stlink_usb_write_mem8(void *handle, uint32_t addr, uint16_t len,
                           const uint8_t *buffer)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       /* max 8bit read/write is 64bytes */
+       if (len > STLINK_MAX_RW8) {
+               LOG_DEBUG("max buffer length exceeded");
+               return ERROR_FAIL;
+       }
 
-       stlink_usb_init_buffer(handle, STLINK_TX_EP, len);
+       stlink_usb_init_buffer(handle, h->tx_ep, len);
 
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_WRITEMEM_8BIT;
@@ -1071,19 +1741,93 @@ static int stlink_usb_write_mem8(void *handle, uint32_t addr, uint16_t len,
 }
 
 /** */
-static int stlink_usb_read_mem32(void *handle, uint32_t addr, uint16_t len,
+static int stlink_usb_read_mem16(void *handle, uint32_t addr, uint16_t len,
                          uint8_t *buffer)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
+
+       assert(handle != NULL);
+
+       if (!(h->version.flags & STLINK_F_HAS_MEM_16BIT))
+               return ERROR_COMMAND_NOTFOUND;
+
+       /* data must be a multiple of 2 and half-word aligned */
+       if (len % 2 || addr % 2) {
+               LOG_DEBUG("Invalid data alignment");
+               return ERROR_TARGET_UNALIGNED_ACCESS;
+       }
+
+       stlink_usb_init_buffer(handle, h->rx_ep, len);
+
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_READMEM_16BIT;
+       h_u32_to_le(h->cmdbuf+h->cmdidx, addr);
+       h->cmdidx += 4;
+       h_u16_to_le(h->cmdbuf+h->cmdidx, len);
+       h->cmdidx += 2;
+
+       res = stlink_usb_xfer(handle, h->databuf, len);
+
+       if (res != ERROR_OK)
+               return res;
+
+       memcpy(buffer, h->databuf, len);
+
+       return stlink_usb_get_rw_status(handle);
+}
+
+/** */
+static int stlink_usb_write_mem16(void *handle, uint32_t addr, uint16_t len,
+                          const uint8_t *buffer)
+{
+       int res;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
+       if (!(h->version.flags & STLINK_F_HAS_MEM_16BIT))
+               return ERROR_COMMAND_NOTFOUND;
+
+       /* data must be a multiple of 2 and half-word aligned */
+       if (len % 2 || addr % 2) {
+               LOG_DEBUG("Invalid data alignment");
+               return ERROR_TARGET_UNALIGNED_ACCESS;
+       }
+
+       stlink_usb_init_buffer(handle, h->tx_ep, len);
+
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
+       h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_WRITEMEM_16BIT;
+       h_u32_to_le(h->cmdbuf+h->cmdidx, addr);
+       h->cmdidx += 4;
+       h_u16_to_le(h->cmdbuf+h->cmdidx, len);
+       h->cmdidx += 2;
+
+       res = stlink_usb_xfer(handle, buffer, len);
 
-       len *= 4;
+       if (res != ERROR_OK)
+               return res;
 
-       stlink_usb_init_buffer(handle, STLINK_RX_EP, len);
+       return stlink_usb_get_rw_status(handle);
+}
+
+/** */
+static int stlink_usb_read_mem32(void *handle, uint32_t addr, uint16_t len,
+                         uint8_t *buffer)
+{
+       int res;
+       struct stlink_usb_handle_s *h = handle;
+
+       assert(handle != NULL);
+
+       /* data must be a multiple of 4 and word aligned */
+       if (len % 4 || addr % 4) {
+               LOG_DEBUG("Invalid data alignment");
+               return ERROR_TARGET_UNALIGNED_ACCESS;
+       }
+
+       stlink_usb_init_buffer(handle, h->rx_ep, len);
 
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_READMEM_32BIT;
@@ -1107,15 +1851,17 @@ static int stlink_usb_write_mem32(void *handle, uint32_t addr, uint16_t len,
                           const uint8_t *buffer)
 {
        int res;
-       struct stlink_usb_handle_s *h;
+       struct stlink_usb_handle_s *h = handle;
 
        assert(handle != NULL);
 
-       h = (struct stlink_usb_handle_s *)handle;
-
-       len *= 4;
+       /* data must be a multiple of 4 and word aligned */
+       if (len % 4 || addr % 4) {
+               LOG_DEBUG("Invalid data alignment");
+               return ERROR_TARGET_UNALIGNED_ACCESS;
+       }
 
-       stlink_usb_init_buffer(handle, STLINK_TX_EP, len);
+       stlink_usb_init_buffer(handle, h->tx_ep, len);
 
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_COMMAND;
        h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_WRITEMEM_32BIT;
@@ -1132,16 +1878,372 @@ static int stlink_usb_write_mem32(void *handle, uint32_t addr, uint16_t len,
        return stlink_usb_get_rw_status(handle);
 }
 
+static uint32_t stlink_max_block_size(uint32_t tar_autoincr_block, uint32_t address)
+{
+       uint32_t max_tar_block = (tar_autoincr_block - ((tar_autoincr_block - 1) & address));
+       if (max_tar_block == 0)
+               max_tar_block = 4;
+       return max_tar_block;
+}
+
+static int stlink_usb_read_mem(void *handle, uint32_t addr, uint32_t size,
+               uint32_t count, uint8_t *buffer)
+{
+       int retval = ERROR_OK;
+       uint32_t bytes_remaining;
+       int retries = 0;
+       struct stlink_usb_handle_s *h = handle;
+
+       /* calculate byte count */
+       count *= size;
+
+       /* switch to 8 bit if stlink does not support 16 bit memory read */
+       if (size == 2 && !(h->version.flags & STLINK_F_HAS_MEM_16BIT))
+               size = 1;
+
+       while (count) {
+
+               bytes_remaining = (size != 1) ? \
+                               stlink_max_block_size(h->max_mem_packet, addr) : STLINK_MAX_RW8;
+
+               if (count < bytes_remaining)
+                       bytes_remaining = count;
+
+               if (h->transport == HL_TRANSPORT_SWIM) {
+                       retval = stlink_swim_readbytes(handle, addr, bytes_remaining, buffer);
+                       if (retval != ERROR_OK)
+                               return retval;
+               } else
+               /*
+                * all stlink support 8/32bit memory read/writes and only from
+                * stlink V2J26 there is support for 16 bit memory read/write.
+                * Honour 32 bit and, if possible, 16 bit too. Otherwise, handle
+                * as 8bit access.
+                */
+               if (size != 1) {
+
+                       /* When in jtag mode the stlink uses the auto-increment functionality.
+                        * However it expects us to pass the data correctly, this includes
+                        * alignment and any page boundaries. We already do this as part of the
+                        * adi_v5 implementation, but the stlink is a hla adapter and so this
+                        * needs implementing manually.
+                        * currently this only affects jtag mode, according to ST they do single
+                        * access in SWD mode - but this may change and so we do it for both modes */
+
+                       /* we first need to check for any unaligned bytes */
+                       if (addr & (size - 1)) {
+
+                               uint32_t head_bytes = size - (addr & (size - 1));
+                               retval = stlink_usb_read_mem8(handle, addr, head_bytes, buffer);
+                               if (retval == ERROR_WAIT && retries < MAX_WAIT_RETRIES) {
+                                       usleep((1<<retries++) * 1000);
+                                       continue;
+                               }
+                               if (retval != ERROR_OK)
+                                       return retval;
+                               buffer += head_bytes;
+                               addr += head_bytes;
+                               count -= head_bytes;
+                               bytes_remaining -= head_bytes;
+                       }
+
+                       if (bytes_remaining & (size - 1))
+                               retval = stlink_usb_read_mem(handle, addr, 1, bytes_remaining, buffer);
+                       else if (size == 2)
+                               retval = stlink_usb_read_mem16(handle, addr, bytes_remaining, buffer);
+                       else
+                               retval = stlink_usb_read_mem32(handle, addr, bytes_remaining, buffer);
+               } else
+                       retval = stlink_usb_read_mem8(handle, addr, bytes_remaining, buffer);
+
+               if (retval == ERROR_WAIT && retries < MAX_WAIT_RETRIES) {
+                       usleep((1<<retries++) * 1000);
+                       continue;
+               }
+               if (retval != ERROR_OK)
+                       return retval;
+
+               buffer += bytes_remaining;
+               addr += bytes_remaining;
+               count -= bytes_remaining;
+       }
+
+       return retval;
+}
+
+static int stlink_usb_write_mem(void *handle, uint32_t addr, uint32_t size,
+               uint32_t count, const uint8_t *buffer)
+{
+       int retval = ERROR_OK;
+       uint32_t bytes_remaining;
+       int retries = 0;
+       struct stlink_usb_handle_s *h = handle;
+
+       /* calculate byte count */
+       count *= size;
+
+       /* switch to 8 bit if stlink does not support 16 bit memory read */
+       if (size == 2 && !(h->version.flags & STLINK_F_HAS_MEM_16BIT))
+               size = 1;
+
+       while (count) {
+
+               bytes_remaining = (size != 1) ? \
+                               stlink_max_block_size(h->max_mem_packet, addr) : STLINK_MAX_RW8;
+
+               if (count < bytes_remaining)
+                       bytes_remaining = count;
+
+               if (h->transport == HL_TRANSPORT_SWIM) {
+                       retval = stlink_swim_writebytes(handle, addr, bytes_remaining, buffer);
+                       if (retval != ERROR_OK)
+                               return retval;
+               } else
+               /*
+                * all stlink support 8/32bit memory read/writes and only from
+                * stlink V2J26 there is support for 16 bit memory read/write.
+                * Honour 32 bit and, if possible, 16 bit too. Otherwise, handle
+                * as 8bit access.
+                */
+               if (size != 1) {
+
+                       /* When in jtag mode the stlink uses the auto-increment functionality.
+                        * However it expects us to pass the data correctly, this includes
+                        * alignment and any page boundaries. We already do this as part of the
+                        * adi_v5 implementation, but the stlink is a hla adapter and so this
+                        * needs implementing manually.
+                        * currently this only affects jtag mode, according to ST they do single
+                        * access in SWD mode - but this may change and so we do it for both modes */
+
+                       /* we first need to check for any unaligned bytes */
+                       if (addr & (size - 1)) {
+
+                               uint32_t head_bytes = size - (addr & (size - 1));
+                               retval = stlink_usb_write_mem8(handle, addr, head_bytes, buffer);
+                               if (retval == ERROR_WAIT && retries < MAX_WAIT_RETRIES) {
+                                       usleep((1<<retries++) * 1000);
+                                       continue;
+                               }
+                               if (retval != ERROR_OK)
+                                       return retval;
+                               buffer += head_bytes;
+                               addr += head_bytes;
+                               count -= head_bytes;
+                               bytes_remaining -= head_bytes;
+                       }
+
+                       if (bytes_remaining & (size - 1))
+                               retval = stlink_usb_write_mem(handle, addr, 1, bytes_remaining, buffer);
+                       else if (size == 2)
+                               retval = stlink_usb_write_mem16(handle, addr, bytes_remaining, buffer);
+                       else
+                               retval = stlink_usb_write_mem32(handle, addr, bytes_remaining, buffer);
+
+               } else
+                       retval = stlink_usb_write_mem8(handle, addr, bytes_remaining, buffer);
+               if (retval == ERROR_WAIT && retries < MAX_WAIT_RETRIES) {
+                       usleep((1<<retries++) * 1000);
+                       continue;
+               }
+               if (retval != ERROR_OK)
+                       return retval;
+
+               buffer += bytes_remaining;
+               addr += bytes_remaining;
+               count -= bytes_remaining;
+       }
+
+       return retval;
+}
+
+/** */
+static int stlink_usb_override_target(const char *targetname)
+{
+       return !strcmp(targetname, "cortex_m");
+}
+
+static int stlink_speed_swim(void *handle, int khz, bool query)
+{
+       /*
+                       we dont care what the khz rate is
+                       we only have low and high speed...
+                       before changing speed the SWIM_CSR HS bit
+                       must be updated
+        */
+       if (khz == 0)
+               stlink_swim_speed(handle, 0);
+       else
+               stlink_swim_speed(handle, 1);
+       return khz;
+}
+
+static int stlink_match_speed_map(const struct speed_map *map, unsigned int map_size, int khz, bool query)
+{
+       unsigned int i;
+       int speed_index = -1;
+       int speed_diff = INT_MAX;
+       bool match = true;
+
+       for (i = 0; i < map_size; i++) {
+               if (khz == map[i].speed) {
+                       speed_index = i;
+                       break;
+               } else {
+                       int current_diff = khz - map[i].speed;
+                       /* get abs value for comparison */
+                       current_diff = (current_diff > 0) ? current_diff : -current_diff;
+                       if ((current_diff < speed_diff) && khz >= map[i].speed) {
+                               speed_diff = current_diff;
+                               speed_index = i;
+                       }
+               }
+       }
+
+       if (speed_index == -1) {
+               /* this will only be here if we cannot match the slow speed.
+                * use the slowest speed we support.*/
+               speed_index = map_size - 1;
+               match = false;
+       } else if (i == map_size)
+               match = false;
+
+       if (!match && query) {
+               LOG_INFO("Unable to match requested speed %d kHz, using %d kHz", \
+                               khz, map[speed_index].speed);
+       }
+
+       return speed_index;
+}
+
+static int stlink_speed_swd(void *handle, int khz, bool query)
+{
+       int speed_index;
+       struct stlink_usb_handle_s *h = handle;
+
+       /* old firmware cannot change it */
+       if (!(h->version.flags & STLINK_F_HAS_SWD_SET_FREQ))
+               return khz;
+
+       speed_index = stlink_match_speed_map(stlink_khz_to_speed_map_swd,
+               ARRAY_SIZE(stlink_khz_to_speed_map_swd), khz, query);
+
+       if (!query) {
+               int result = stlink_usb_set_swdclk(h, stlink_khz_to_speed_map_swd[speed_index].speed_divisor);
+               if (result != ERROR_OK) {
+                       LOG_ERROR("Unable to set adapter speed");
+                       return khz;
+               }
+       }
+
+       return stlink_khz_to_speed_map_swd[speed_index].speed;
+}
+
+static int stlink_speed_jtag(void *handle, int khz, bool query)
+{
+       int speed_index;
+       struct stlink_usb_handle_s *h = handle;
+
+       /* old firmware cannot change it */
+       if (!(h->version.flags & STLINK_F_HAS_JTAG_SET_FREQ))
+               return khz;
+
+       speed_index = stlink_match_speed_map(stlink_khz_to_speed_map_jtag,
+               ARRAY_SIZE(stlink_khz_to_speed_map_jtag), khz, query);
+
+       if (!query) {
+               int result = stlink_usb_set_jtagclk(h, stlink_khz_to_speed_map_jtag[speed_index].speed_divisor);
+               if (result != ERROR_OK) {
+                       LOG_ERROR("Unable to set adapter speed");
+                       return khz;
+               }
+       }
+
+       return stlink_khz_to_speed_map_jtag[speed_index].speed;
+}
+
+void stlink_dump_speed_map(const struct speed_map *map, unsigned int map_size)
+{
+       unsigned int i;
+
+       LOG_DEBUG("Supported clock speeds are:");
+       for (i = 0; i < map_size; i++)
+               LOG_DEBUG("%d kHz", map[i].speed);
+}
+
+static int stlink_speed(void *handle, int khz, bool query)
+{
+       struct stlink_usb_handle_s *h = handle;
+
+       if (!handle)
+               return khz;
+
+       if (h->transport == HL_TRANSPORT_SWIM)
+               return stlink_speed_swim(handle, khz, query);
+       else if (h->transport == HL_TRANSPORT_SWD)
+               return stlink_speed_swd(handle, khz, query);
+       else if (h->transport == HL_TRANSPORT_JTAG)
+               return stlink_speed_jtag(handle, khz, query);
+
+       return khz;
+}
+
 /** */
-static int stlink_usb_open(struct stlink_interface_param_s *param, void **fd)
+static int stlink_usb_close(void *handle)
 {
-       int err;
+       int res;
+       uint8_t mode;
+       enum stlink_mode emode;
+       struct stlink_usb_handle_s *h = handle;
+
+       if (h && h->fd)
+               res = stlink_usb_current_mode(handle, &mode);
+       else
+               res = ERROR_FAIL;
+       /* do not exit if return code != ERROR_OK,
+          it prevents us from closing jtag_libusb */
+
+       if (res == ERROR_OK) {
+               /* try to exit current mode */
+               switch (mode) {
+                       case STLINK_DEV_DFU_MODE:
+                               emode = STLINK_MODE_DFU;
+                               break;
+                       case STLINK_DEV_DEBUG_MODE:
+                               emode = STLINK_MODE_DEBUG_SWD;
+                               break;
+                       case STLINK_DEV_SWIM_MODE:
+                               emode = STLINK_MODE_DEBUG_SWIM;
+                               break;
+                       case STLINK_DEV_BOOTLOADER_MODE:
+                       case STLINK_DEV_MASS_MODE:
+                       default:
+                               emode = STLINK_MODE_UNKNOWN;
+                               break;
+               }
+
+               if (emode != STLINK_MODE_UNKNOWN)
+                       stlink_usb_mode_leave(handle, emode);
+                       /* do not check return code, it prevent
+                       us from closing jtag_libusb */
+       }
+
+       if (h && h->fd)
+               jtag_libusb_close(h->fd);
+
+       free(h);
+
+       return ERROR_OK;
+}
+
+/** */
+static int stlink_usb_open(struct hl_interface_param_s *param, void **fd)
+{
+       int err, retry_count = 1;
        struct stlink_usb_handle_s *h;
-       enum stlink_jtag_api_version api;
 
        LOG_DEBUG("stlink_usb_open");
 
-       h = malloc(sizeof(struct stlink_usb_handle_s));
+       h = calloc(1, sizeof(struct stlink_usb_handle_s));
 
        if (h == 0) {
                LOG_DEBUG("malloc failed");
@@ -1150,60 +2252,109 @@ static int stlink_usb_open(struct stlink_interface_param_s *param, void **fd)
 
        h->transport = param->transport;
 
-       const uint16_t vids[] = { param->vid, 0 };
-       const uint16_t pids[] = { param->pid, 0 };
+       for (unsigned i = 0; param->vid[i]; i++) {
+               LOG_DEBUG("transport: %d vid: 0x%04x pid: 0x%04x serial: %s",
+                         param->transport, param->vid[i], param->pid[i],
+                         param->serial ? param->serial : "");
+       }
+
+       /*
+         On certain host USB configurations(e.g. MacBook Air)
+         STLINKv2 dongle seems to have its FW in a funky state if,
+         after plugging it in, you try to use openocd with it more
+         then once (by launching and closing openocd). In cases like
+         that initial attempt to read the FW info via
+         stlink_usb_version will fail and the device has to be reset
+         in order to become operational.
+        */
+       do {
+               if (jtag_libusb_open(param->vid, param->pid, param->serial, &h->fd) != ERROR_OK) {
+                       LOG_ERROR("open failed");
+                       goto error_open;
+               }
 
-       LOG_DEBUG("transport: %d vid: 0x%04x pid: 0x%04x", param->transport,
-               param->vid, param->pid);
+               jtag_libusb_set_configuration(h->fd, 0);
 
-       if (jtag_libusb_open(vids, pids, &h->fd) != ERROR_OK) {
-               LOG_ERROR("open failed");
-               return ERROR_FAIL;
-       }
+               if (jtag_libusb_claim_interface(h->fd, 0) != ERROR_OK) {
+                       LOG_DEBUG("claim interface failed");
+                       goto error_open;
+               }
 
-       jtag_libusb_set_configuration(h->fd, 0);
+               /* RX EP is common for all versions */
+               h->rx_ep = STLINK_RX_EP;
 
-       if (jtag_libusb_claim_interface(h->fd, 0) != ERROR_OK) {
-               LOG_DEBUG("claim interface failed");
-               return ERROR_FAIL;
-       }
+               uint16_t pid;
+               if (jtag_libusb_get_pid(jtag_libusb_get_device(h->fd), &pid) != ERROR_OK) {
+                       LOG_DEBUG("libusb_get_pid failed");
+                       goto error_open;
+               }
 
-       /* wrap version for first read */
-       switch (param->pid) {
-               case 0x3744:
-                       h->version.stlink = 1;
-                       break;
-               default:
-                       h->version.stlink = 2;
-                       break;
-       }
+               /* wrap version for first read */
+               switch (pid) {
+                       case STLINK_V1_PID:
+                               h->version.stlink = 1;
+                               h->tx_ep = STLINK_TX_EP;
+                               break;
+                       case STLINK_V2_1_PID:
+                       case STLINK_V2_1_NO_MSD_PID:
+                               h->version.stlink = 2;
+                               h->tx_ep = STLINK_V2_1_TX_EP;
+                               h->trace_ep = STLINK_V2_1_TRACE_EP;
+                               break;
+                       default:
+                       /* fall through - we assume V2 to be the default version*/
+                       case STLINK_V2_PID:
+                               h->version.stlink = 2;
+                               h->tx_ep = STLINK_TX_EP;
+                               h->trace_ep = STLINK_TRACE_EP;
+                               break;
+               }
 
-       /* get the device version */
-       err = stlink_usb_version(h);
+               /* get the device version */
+               err = stlink_usb_version(h);
 
-       if (err != ERROR_OK) {
-               LOG_ERROR("read version failed");
-               jtag_libusb_close(h->fd);
-               free(h);
-               return err;
-       }
+               if (err == ERROR_OK) {
+                       break;
+               } else if (h->version.stlink == 1 ||
+                          retry_count == 0) {
+                       LOG_ERROR("read version failed");
+                       goto error_open;
+               } else {
+                       err = jtag_libusb_release_interface(h->fd, 0);
+                       if (err != ERROR_OK) {
+                               LOG_ERROR("release interface failed");
+                               goto error_open;
+                       }
+
+                       err = jtag_libusb_reset_device(h->fd);
+                       if (err != ERROR_OK) {
+                               LOG_ERROR("reset device failed");
+                               goto error_open;
+                       }
 
-       /* compare usb vid/pid */
-       if ((param->vid != h->vid) || (param->pid != h->pid))
-               LOG_INFO("vid/pid are not identical: 0x%04X/0x%04X 0x%04X/0x%04X",
-                       param->vid, param->pid,
-                       h->vid, h->pid);
+                       jtag_libusb_close(h->fd);
+                       /*
+                         Give the device one second to settle down and
+                         reenumerate.
+                        */
+                       usleep(1 * 1000 * 1000);
+                       retry_count--;
+               }
+       } while (1);
 
        /* check if mode is supported */
        err = ERROR_OK;
 
        switch (h->transport) {
-               case STLINK_TRANSPORT_SWD:
-               case STLINK_TRANSPORT_JTAG:
+               case HL_TRANSPORT_SWD:
+                       if (h->version.jtag_api == STLINK_JTAG_API_V1)
+                               err = ERROR_FAIL;
+                       /* fall-through */
+               case HL_TRANSPORT_JTAG:
                        if (h->version.jtag == 0)
                                err = ERROR_FAIL;
                        break;
-               case STLINK_TRANSPORT_SWIM:
+               case HL_TRANSPORT_SWIM:
                        if (h->version.swim == 0)
                                err = ERROR_FAIL;
                        break;
@@ -1214,46 +2365,100 @@ static int stlink_usb_open(struct stlink_interface_param_s *param, void **fd)
 
        if (err != ERROR_OK) {
                LOG_ERROR("mode (transport) not supported by device");
-               jtag_libusb_close(h->fd);
-               free(h);
-               return err;
+               goto error_open;
        }
 
-       api = h->version.jtag_api_max;
+       /* initialize the debug hardware */
+       err = stlink_usb_init_mode(h, param->connect_under_reset);
 
-       /* check that user has not requested certain api version
-        * and if they have check it is supported */
-       if ((param->api != 0) && (param->api <= h->version.jtag_api_max)) {
-               api = param->api;
-               LOG_INFO("using stlink api v%d", api);
+       if (err != ERROR_OK) {
+               LOG_ERROR("init mode failed (unable to connect to the target)");
+               goto error_open;
        }
 
-       /* set the used jtag api, this will default to the newest supported version */
-       h->jtag_api = api;
+       if (h->transport == HL_TRANSPORT_SWIM) {
+               err = stlink_swim_enter(h);
+               if (err != ERROR_OK) {
+                       LOG_ERROR("stlink_swim_enter_failed (unable to connect to the target)");
+                       goto error_open;
+               }
+               *fd = h;
+               h->max_mem_packet = STLINK_DATA_SIZE;
+               return ERROR_OK;
+       }
 
-       /* initialize the debug hardware */
-       err = stlink_usb_init_mode(h);
+       if (h->transport == HL_TRANSPORT_JTAG) {
+               if (h->version.flags & STLINK_F_HAS_JTAG_SET_FREQ) {
+                       stlink_dump_speed_map(stlink_khz_to_speed_map_jtag, ARRAY_SIZE(stlink_khz_to_speed_map_jtag));
+                       stlink_speed(h, param->initial_interface_speed, false);
+               }
+       } else if (h->transport == HL_TRANSPORT_SWD) {
+               if (h->version.flags & STLINK_F_HAS_SWD_SET_FREQ) {
+                       stlink_dump_speed_map(stlink_khz_to_speed_map_swd, ARRAY_SIZE(stlink_khz_to_speed_map_swd));
+                       stlink_speed(h, param->initial_interface_speed, false);
+               }
+       }
 
-       if (err != ERROR_OK) {
-               LOG_ERROR("init mode failed");
-               jtag_libusb_close(h->fd);
-               free(h);
-               return err;
+       /* get cpuid, so we can determine the max page size
+        * start with a safe default */
+       h->max_mem_packet = (1 << 10);
+
+       uint8_t buffer[4];
+       err = stlink_usb_read_mem32(h, CPUID, 4, buffer);
+       if (err == ERROR_OK) {
+               uint32_t cpuid = le_to_h_u32(buffer);
+               int i = (cpuid >> 4) & 0xf;
+               if (i == 4 || i == 3) {
+                       /* Cortex-M3/M4 has 4096 bytes autoincrement range */
+                       h->max_mem_packet = (1 << 12);
+               }
        }
 
+       LOG_DEBUG("Using TAR autoincrement: %" PRIu32, h->max_mem_packet);
+
        *fd = h;
 
        return ERROR_OK;
+
+error_open:
+       stlink_usb_close(h);
+
+       return ERROR_FAIL;
 }
 
-/** */
-static int stlink_usb_close(void *fd)
+int stlink_config_trace(void *handle, bool enabled, enum tpiu_pin_protocol pin_protocol,
+                       uint32_t port_size, unsigned int *trace_freq)
 {
-       return ERROR_OK;
+       struct stlink_usb_handle_s *h = handle;
+
+       if (enabled && (!(h->version.flags & STLINK_F_HAS_TRACE) ||
+                       pin_protocol != TPIU_PIN_PROTOCOL_ASYNC_UART)) {
+               LOG_ERROR("The attached ST-LINK version doesn't support this trace mode");
+               return ERROR_FAIL;
+       }
+
+       if (!enabled) {
+               stlink_usb_trace_disable(h);
+               return ERROR_OK;
+       }
+
+       if (*trace_freq > STLINK_TRACE_MAX_HZ) {
+               LOG_ERROR("ST-LINK doesn't support SWO frequency higher than %u",
+                         STLINK_TRACE_MAX_HZ);
+               return ERROR_FAIL;
+       }
+
+       stlink_usb_trace_disable(h);
+
+       if (!*trace_freq)
+               *trace_freq = STLINK_TRACE_MAX_HZ;
+       h->trace.source_hz = *trace_freq;
+
+       return stlink_usb_trace_enable(h);
 }
 
 /** */
-struct stlink_layout_api_s stlink_usb_layout_api = {
+struct hl_layout_api_s stlink_usb_layout_api = {
        /** */
        .open = stlink_usb_open,
        /** */
@@ -1279,13 +2484,17 @@ struct stlink_layout_api_s stlink_usb_layout_api = {
        /** */
        .write_reg = stlink_usb_write_reg,
        /** */
-       .read_mem8 = stlink_usb_read_mem8,
+       .read_mem = stlink_usb_read_mem,
+       /** */
+       .write_mem = stlink_usb_write_mem,
+       /** */
+       .write_debug_reg = stlink_usb_write_debug_reg,
        /** */
-       .write_mem8 = stlink_usb_write_mem8,
+       .override_target = stlink_usb_override_target,
        /** */
-       .read_mem32 = stlink_usb_read_mem32,
+       .speed = stlink_speed,
        /** */
-       .write_mem32 = stlink_usb_write_mem32,
+       .config_trace = stlink_config_trace,
        /** */
-       .write_debug_reg = stlink_usb_write_debug_reg
+       .poll_trace = stlink_usb_trace_read,
 };