flash/nor/at91samd: Use 32-bit register writes for ST-Link compat
[fw/openocd] / src / flash / nor / at91samd.c
index 7c877c0ff87d0b99a62ed5bf1fa7c267d341eb67..3b8893252a32d56ffd2467596424aa67abed1915 100644 (file)
@@ -1,21 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
 /***************************************************************************
  *   Copyright (C) 2013 by Andrey Yurovsky                                 *
  *   Andrey Yurovsky <yurovsky@gmail.com>                                  *
- *                                                                         *
- *   This program is free software; you can redistribute it and/or modify  *
- *   it under the terms of the GNU General Public License as published by  *
- *   the Free Software Foundation; either version 2 of the License, or     *
- *   (at your option) any later version.                                   *
- *                                                                         *
- *   This program is distributed in the hope that it will be useful,       *
- *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
- *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
- *   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.,                                       *
- *   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.           *
  ***************************************************************************/
 
 #ifdef HAVE_CONFIG_H
 #include "imp.h"
 #include "helper/binarybuffer.h"
 
-#define SAMD_NUM_SECTORS       16
+#include <jtag/jtag.h>
+#include <target/cortex_m.h>
+
+#define SAMD_NUM_PROT_BLOCKS   16
 #define SAMD_PAGE_SIZE_MAX     1024
 
 #define SAMD_FLASH                     ((uint32_t)0x00000000)  /* physical Flash memory */
 #define SAMD_DSU                       0x41002000      /* Device Service Unit */
 #define SAMD_NVMCTRL           0x41004000      /* Non-volatile memory controller */
 
+#define SAMD_DSU_STATUSA        1               /* DSU status register */
 #define SAMD_DSU_DID           0x18            /* Device ID register */
+#define SAMD_DSU_CTRL_EXT      0x100           /* CTRL register, external access */
 
 #define SAMD_NVMCTRL_CTRLA             0x00    /* NVM control A register */
 #define SAMD_NVMCTRL_CTRLB             0x04    /* NVM control B register */
 #define SAMD_NVMCTRL_PARAM             0x08    /* NVM parameters register */
-#define SAMD_NVMCTRL_INTFLAG   0x18    /* NVM Interupt Flag Status & Clear */
+#define SAMD_NVMCTRL_INTFLAG   0x18    /* NVM Interrupt Flag Status & Clear */
 #define SAMD_NVMCTRL_STATUS            0x18    /* NVM status register */
 #define SAMD_NVMCTRL_ADDR              0x1C    /* NVM address register */
 #define SAMD_NVMCTRL_LOCK              0x20    /* NVM Lock section register */
@@ -50,8 +42,8 @@
 /* NVMCTRL commands.  See Table 20-4 in 42129F–SAM–10/2013 */
 #define SAMD_NVM_CMD_ER                0x02            /* Erase Row */
 #define SAMD_NVM_CMD_WP                0x04            /* Write Page */
-#define SAMD_NVM_CMD_EAR       0x05            /* Erase Auxilary Row */
-#define SAMD_NVM_CMD_WAP       0x06            /* Write Auxilary Page */
+#define SAMD_NVM_CMD_EAR       0x05            /* Erase Auxiliary Row */
+#define SAMD_NVM_CMD_WAP       0x06            /* Write Auxiliary Page */
 #define SAMD_NVM_CMD_LR                0x40            /* Lock Region */
 #define SAMD_NVM_CMD_UR                0x41            /* Unlock Region */
 #define SAMD_NVM_CMD_SPRM      0x42            /* Set Power Reduction Mode */
 #define SAMD_NVM_CMD_SSB       0x45            /* Set Security Bit */
 #define SAMD_NVM_CMD_INVALL    0x46            /* Invalidate all caches */
 
+/* NVMCTRL bits */
+#define SAMD_NVM_CTRLB_MANW 0x80
+
 /* Known identifiers */
 #define SAMD_PROCESSOR_M0      0x01
 #define SAMD_FAMILY_D          0x00
+#define SAMD_FAMILY_L          0x01
+#define SAMD_FAMILY_C          0x02
 #define SAMD_SERIES_20         0x00
 #define SAMD_SERIES_21         0x01
+#define SAMD_SERIES_22         0x02
 #define SAMD_SERIES_10         0x02
 #define SAMD_SERIES_11         0x03
+#define SAMD_SERIES_09         0x04
+
+/* Device ID macros */
+#define SAMD_GET_PROCESSOR(id) (id >> 28)
+#define SAMD_GET_FAMILY(id) (((id >> 23) & 0x1F))
+#define SAMD_GET_SERIES(id) (((id >> 16) & 0x3F))
+#define SAMD_GET_DEVSEL(id) (id & 0xFF)
+
+/* Bits to mask out lockbits in user row */
+#define NVMUSERROW_LOCKBIT_MASK ((uint64_t)0x0000FFFFFFFFFFFF)
 
 struct samd_part {
        uint8_t id;
@@ -75,6 +83,13 @@ struct samd_part {
        uint32_t ram_kb;
 };
 
+/* Known SAMD09 parts. DID reset values missing in RM, see
+ * https://github.com/avrxml/asf/blob/master/sam0/utils/cmsis/samd09/include/ */
+static const struct samd_part samd09_parts[] = {
+       { 0x0, "SAMD09D14A", 16, 4 },
+       { 0x7, "SAMD09C13A", 8, 4 },
+};
+
 /* Known SAMD10 parts */
 static const struct samd_part samd10_parts[] = {
        { 0x0, "SAMD10D14AMU", 16, 4 },
@@ -90,15 +105,16 @@ static const struct samd_part samd10_parts[] = {
 
 /* Known SAMD11 parts */
 static const struct samd_part samd11_parts[] = {
-       { 0x0, "SAMD11D14AMU", 16, 4 },
+       { 0x0, "SAMD11D14AM", 16, 4 },
        { 0x1, "SAMD11D13AMU", 8, 4 },
        { 0x2, "SAMD11D12AMU", 4, 4 },
-       { 0x3, "SAMD11D14ASU", 16, 4 },
+       { 0x3, "SAMD11D14ASS", 16, 4 },
        { 0x4, "SAMD11D13ASU", 8, 4 },
        { 0x5, "SAMD11D12ASU", 4, 4 },
        { 0x6, "SAMD11C14A", 16, 4 },
        { 0x7, "SAMD11C13A", 8, 4 },
        { 0x8, "SAMD11C12A", 4, 4 },
+       { 0x9, "SAMD11D14AU", 16, 4 },
 };
 
 /* Known SAMD20 parts. See Table 12-8 in 42129F–SAM–10/2013 */
@@ -137,18 +153,144 @@ static const struct samd_part samd21_parts[] = {
        { 0xC, "SAMD21E16A", 64, 8 },
        { 0xD, "SAMD21E15A", 32, 4 },
        { 0xE, "SAMD21E14A", 16, 2 },
-};
 
-/* Known SAMR21 parts. */
-static const struct samd_part samr21_parts[] = {
+    /* SAMR21 parts have integrated SAMD21 with a radio */
+       { 0x18, "SAMR21G19A", 256, 32 }, /* with 512k of serial flash */
        { 0x19, "SAMR21G18A", 256, 32 },
        { 0x1A, "SAMR21G17A", 128, 32 },
-       { 0x1B, "SAMR21G16A",  64, 32 },
+       { 0x1B, "SAMR21G16A",  64, 16 },
        { 0x1C, "SAMR21E18A", 256, 32 },
        { 0x1D, "SAMR21E17A", 128, 32 },
-       { 0x1E, "SAMR21E16A",  64, 32 },
+       { 0x1E, "SAMR21E16A",  64, 16 },
+
+    /* SAMD21 B Variants (Table 3-7 from rev I of datasheet) */
+       { 0x20, "SAMD21J16B", 64, 8 },
+       { 0x21, "SAMD21J15B", 32, 4 },
+       { 0x23, "SAMD21G16B", 64, 8 },
+       { 0x24, "SAMD21G15B", 32, 4 },
+       { 0x26, "SAMD21E16B", 64, 8 },
+       { 0x27, "SAMD21E15B", 32, 4 },
+
+       /* SAMD21 D and L Variants (from Errata)
+          http://ww1.microchip.com/downloads/en/DeviceDoc/
+          SAM-D21-Family-Silicon-Errata-and-DataSheet-Clarification-DS80000760D.pdf */
+       { 0x55, "SAMD21E16BU", 64, 8 },
+       { 0x56, "SAMD21E15BU", 32, 4 },
+       { 0x57, "SAMD21G16L", 64, 8 },
+       { 0x3E, "SAMD21E16L", 64, 8 },
+       { 0x3F, "SAMD21E15L", 32, 4 },
+       { 0x62, "SAMD21E16CU", 64, 8 },
+       { 0x63, "SAMD21E15CU", 32, 4 },
+       { 0x92, "SAMD21J17D", 128, 16 },
+       { 0x93, "SAMD21G17D", 128, 16 },
+       { 0x94, "SAMD21E17D", 128, 16 },
+       { 0x95, "SAMD21E17DU", 128, 16 },
+       { 0x96, "SAMD21G17L", 128, 16 },
+       { 0x97, "SAMD21E17L", 128, 16 },
+
+       /* Known SAMDA1 parts.
+          SAMD-A1 series uses the same series identifier like the SAMD21
+          taken from http://ww1.microchip.com/downloads/en/DeviceDoc/40001895A.pdf (pages 14-17) */
+       { 0x29, "SAMDA1J16A", 64, 8 },
+       { 0x2A, "SAMDA1J15A", 32, 4 },
+       { 0x2B, "SAMDA1J14A", 16, 4 },
+       { 0x2C, "SAMDA1G16A", 64, 8 },
+       { 0x2D, "SAMDA1G15A", 32, 4 },
+       { 0x2E, "SAMDA1G14A", 16, 4 },
+       { 0x2F, "SAMDA1E16A", 64, 8 },
+       { 0x30, "SAMDA1E15A", 32, 4 },
+       { 0x31, "SAMDA1E14A", 16, 4 },
+       { 0x64, "SAMDA1J16B", 64, 8 },
+       { 0x65, "SAMDA1J15B", 32, 4 },
+       { 0x66, "SAMDA1J14B", 16, 4 },
+       { 0x67, "SAMDA1G16B", 64, 8 },
+       { 0x68, "SAMDA1G15B", 32, 4 },
+       { 0x69, "SAMDA1G14B", 16, 4 },
+       { 0x6A, "SAMDA1E16B", 64, 8 },
+       { 0x6B, "SAMDA1E15B", 32, 4 },
+       { 0x6C, "SAMDA1E14B", 16, 4 },
 };
 
+/* Known SAML21 parts. */
+static const struct samd_part saml21_parts[] = {
+       { 0x00, "SAML21J18A", 256, 32 },
+       { 0x01, "SAML21J17A", 128, 16 },
+       { 0x02, "SAML21J16A", 64, 8 },
+       { 0x05, "SAML21G18A", 256, 32 },
+       { 0x06, "SAML21G17A", 128, 16 },
+       { 0x07, "SAML21G16A", 64, 8 },
+       { 0x0A, "SAML21E18A", 256, 32 },
+       { 0x0B, "SAML21E17A", 128, 16 },
+       { 0x0C, "SAML21E16A", 64, 8 },
+       { 0x0D, "SAML21E15A", 32, 4 },
+       { 0x0F, "SAML21J18B", 256, 32 },
+       { 0x10, "SAML21J17B", 128, 16 },
+       { 0x11, "SAML21J16B", 64, 8 },
+       { 0x14, "SAML21G18B", 256, 32 },
+       { 0x15, "SAML21G17B", 128, 16 },
+       { 0x16, "SAML21G16B", 64, 8 },
+       { 0x19, "SAML21E18B", 256, 32 },
+       { 0x1A, "SAML21E17B", 128, 16 },
+       { 0x1B, "SAML21E16B", 64, 8 },
+       { 0x1C, "SAML21E15B", 32, 4 },
+
+    /* SAMR30 parts have integrated SAML21 with a radio */
+       { 0x1E, "SAMR30G18A", 256, 32 },
+       { 0x1F, "SAMR30E18A", 256, 32 },
+
+    /* SAMR34/R35 parts have integrated SAML21 with a lora radio */
+       { 0x28, "SAMR34J18", 256, 32 },
+       { 0x2B, "SAMR35J18", 256, 32 },
+};
+
+/* Known SAML22 parts. */
+static const struct samd_part saml22_parts[] = {
+       { 0x00, "SAML22N18A", 256, 32 },
+       { 0x01, "SAML22N17A", 128, 16 },
+       { 0x02, "SAML22N16A", 64, 8 },
+       { 0x05, "SAML22J18A", 256, 32 },
+       { 0x06, "SAML22J17A", 128, 16 },
+       { 0x07, "SAML22J16A", 64, 8 },
+       { 0x0A, "SAML22G18A", 256, 32 },
+       { 0x0B, "SAML22G17A", 128, 16 },
+       { 0x0C, "SAML22G16A", 64, 8 },
+};
+
+/* Known SAMC20 parts. */
+static const struct samd_part samc20_parts[] = {
+       { 0x00, "SAMC20J18A", 256, 32 },
+       { 0x01, "SAMC20J17A", 128, 16 },
+       { 0x02, "SAMC20J16A", 64, 8 },
+       { 0x03, "SAMC20J15A", 32, 4 },
+       { 0x05, "SAMC20G18A", 256, 32 },
+       { 0x06, "SAMC20G17A", 128, 16 },
+       { 0x07, "SAMC20G16A", 64, 8 },
+       { 0x08, "SAMC20G15A", 32, 4 },
+       { 0x0A, "SAMC20E18A", 256, 32 },
+       { 0x0B, "SAMC20E17A", 128, 16 },
+       { 0x0C, "SAMC20E16A", 64, 8 },
+       { 0x0D, "SAMC20E15A", 32, 4 },
+       { 0x20, "SAMC20N18A", 256, 32 },
+       { 0x21, "SAMC20N17A", 128, 16 },
+};
+
+/* Known SAMC21 parts. */
+static const struct samd_part samc21_parts[] = {
+       { 0x00, "SAMC21J18A", 256, 32 },
+       { 0x01, "SAMC21J17A", 128, 16 },
+       { 0x02, "SAMC21J16A", 64, 8 },
+       { 0x03, "SAMC21J15A", 32, 4 },
+       { 0x05, "SAMC21G18A", 256, 32 },
+       { 0x06, "SAMC21G17A", 128, 16 },
+       { 0x07, "SAMC21G16A", 64, 8 },
+       { 0x08, "SAMC21G15A", 32, 4 },
+       { 0x0A, "SAMC21E18A", 256, 32 },
+       { 0x0B, "SAMC21E17A", 128, 16 },
+       { 0x0C, "SAMC21E16A", 64, 8 },
+       { 0x0D, "SAMC21E15A", 32, 4 },
+       { 0x20, "SAMC21N18A", 256, 32 },
+       { 0x21, "SAMC21N17A", 128, 16 },
+};
 
 /* Each family of parts contains a parts table in the DEVSEL field of DID.  The
  * processor ID, family ID, and series ID are used to determine which exact
@@ -159,50 +301,87 @@ struct samd_family {
        uint8_t series;
        const struct samd_part *parts;
        size_t num_parts;
+       uint64_t nvm_userrow_res_mask; /* protect bits which are reserved, 0 -> protect */
 };
 
 /* Known SAMD families */
 static const struct samd_family samd_families[] = {
        { SAMD_PROCESSOR_M0, SAMD_FAMILY_D, SAMD_SERIES_20,
-               samd20_parts, ARRAY_SIZE(samd20_parts) },
+               samd20_parts, ARRAY_SIZE(samd20_parts),
+               (uint64_t)0xFFFF01FFFE01FF77 },
        { SAMD_PROCESSOR_M0, SAMD_FAMILY_D, SAMD_SERIES_21,
-               samd21_parts, ARRAY_SIZE(samd21_parts) },
-       { SAMD_PROCESSOR_M0, SAMD_FAMILY_D, SAMD_SERIES_21,
-               samr21_parts, ARRAY_SIZE(samr21_parts) },
+               samd21_parts, ARRAY_SIZE(samd21_parts),
+               (uint64_t)0xFFFF01FFFE01FF77 },
+       { SAMD_PROCESSOR_M0, SAMD_FAMILY_D, SAMD_SERIES_09,
+               samd09_parts, ARRAY_SIZE(samd09_parts),
+               (uint64_t)0xFFFF01FFFE01FF77 },
        { SAMD_PROCESSOR_M0, SAMD_FAMILY_D, SAMD_SERIES_10,
-               samd10_parts, ARRAY_SIZE(samd10_parts) },
+               samd10_parts, ARRAY_SIZE(samd10_parts),
+               (uint64_t)0xFFFF01FFFE01FF77 },
        { SAMD_PROCESSOR_M0, SAMD_FAMILY_D, SAMD_SERIES_11,
-               samd11_parts, ARRAY_SIZE(samd11_parts) },
+               samd11_parts, ARRAY_SIZE(samd11_parts),
+               (uint64_t)0xFFFF01FFFE01FF77 },
+       { SAMD_PROCESSOR_M0, SAMD_FAMILY_L, SAMD_SERIES_21,
+               saml21_parts, ARRAY_SIZE(saml21_parts),
+               (uint64_t)0xFFFF03FFFC01FF77 },
+       { SAMD_PROCESSOR_M0, SAMD_FAMILY_L, SAMD_SERIES_22,
+               saml22_parts, ARRAY_SIZE(saml22_parts),
+               (uint64_t)0xFFFF03FFFC01FF77 },
+       { SAMD_PROCESSOR_M0, SAMD_FAMILY_C, SAMD_SERIES_20,
+               samc20_parts, ARRAY_SIZE(samc20_parts),
+               (uint64_t)0xFFFF03FFFC01FF77 },
+       { SAMD_PROCESSOR_M0, SAMD_FAMILY_C, SAMD_SERIES_21,
+               samc21_parts, ARRAY_SIZE(samc21_parts),
+               (uint64_t)0xFFFF03FFFC01FF77 },
 };
 
 struct samd_info {
        uint32_t page_size;
        int num_pages;
        int sector_size;
+       int prot_block_size;
 
        bool probed;
        struct target *target;
-       struct samd_info *next;
 };
 
-static struct samd_info *samd_chips;
 
-static const struct samd_part *samd_find_part(uint32_t id)
+/**
+ * Gives the family structure to specific device id.
+ * @param id The id of the device.
+ * @return On failure NULL, otherwise a pointer to the structure.
+ */
+static const struct samd_family *samd_find_family(uint32_t id)
 {
-       uint8_t processor = (id >> 28);
-       uint8_t family = (id >> 24) & 0x0F;
-       uint8_t series = (id >> 16) & 0xFF;
-       uint8_t devsel = id & 0xFF;
+       uint8_t processor = SAMD_GET_PROCESSOR(id);
+       uint8_t family = SAMD_GET_FAMILY(id);
+       uint8_t series = SAMD_GET_SERIES(id);
 
        for (unsigned i = 0; i < ARRAY_SIZE(samd_families); i++) {
                if (samd_families[i].processor == processor &&
                        samd_families[i].series == series &&
-                       samd_families[i].family == family) {
-                       for (unsigned j = 0; j < samd_families[i].num_parts; j++) {
-                               if (samd_families[i].parts[j].id == devsel)
-                                       return &samd_families[i].parts[j];
-                       }
-               }
+                       samd_families[i].family == family)
+                       return &samd_families[i];
+       }
+
+       return NULL;
+}
+
+/**
+ * Gives the part structure to specific device id.
+ * @param id The id of the device.
+ * @return On failure NULL, otherwise a pointer to the structure.
+ */
+static const struct samd_part *samd_find_part(uint32_t id)
+{
+       uint8_t devsel = SAMD_GET_DEVSEL(id);
+       const struct samd_family *family = samd_find_family(id);
+       if (!family)
+               return NULL;
+
+       for (unsigned i = 0; i < family->num_parts; i++) {
+               if (family->parts[i].id == devsel)
+                       return &family->parts[i];
        }
 
        return NULL;
@@ -219,8 +398,8 @@ static int samd_protect_check(struct flash_bank *bank)
                return res;
 
        /* Lock bits are active-low */
-       for (int i = 0; i < bank->num_sectors; i++)
-               bank->sectors[i].is_protected = !(lock & (1<<i));
+       for (unsigned int prot_block = 0; prot_block < bank->num_prot_blocks; prot_block++)
+               bank->prot_blocks[prot_block].is_protected = !(lock & (1u<<prot_block));
 
        return ERROR_OK;
 }
@@ -264,15 +443,13 @@ static int samd_probe(struct flash_bank *bank)
        }
 
        part = samd_find_part(id);
-       if (part == NULL) {
-               LOG_ERROR("Couldn't find part correspoding to DID %08" PRIx32, id);
+       if (!part) {
+               LOG_ERROR("Couldn't find part corresponding to DID %08" PRIx32, id);
                return ERROR_FAIL;
        }
 
        bank->size = part->flash_kb * 1024;
 
-       chip->sector_size = bank->size / SAMD_NUM_SECTORS;
-
        res = samd_get_flash_page_info(bank->target, &chip->page_size,
                        &chip->num_pages);
        if (res != ERROR_OK) {
@@ -288,21 +465,23 @@ static int samd_probe(struct flash_bank *bank)
                                part->flash_kb, chip->num_pages, chip->page_size);
        }
 
+       /* Erase granularity = 1 row = 4 pages */
+       chip->sector_size = chip->page_size * 4;
+
        /* Allocate the sector table */
-       bank->num_sectors = SAMD_NUM_SECTORS;
-       bank->sectors = calloc(bank->num_sectors, sizeof((bank->sectors)[0]));
+       bank->num_sectors = chip->num_pages / 4;
+       bank->sectors = alloc_block_array(0, chip->sector_size, bank->num_sectors);
        if (!bank->sectors)
                return ERROR_FAIL;
 
-       /* Fill out the sector information: all SAMD sectors are the same size and
-        * there is always a fixed number of them. */
-       for (int i = 0; i < bank->num_sectors; i++) {
-               bank->sectors[i].size = chip->sector_size;
-               bank->sectors[i].offset = i * chip->sector_size;
-               /* mark as unknown */
-               bank->sectors[i].is_erased = -1;
-               bank->sectors[i].is_protected = -1;
-       }
+       /* 16 protection blocks per device */
+       chip->prot_block_size = bank->size / SAMD_NUM_PROT_BLOCKS;
+
+       /* Allocate the table of protection blocks */
+       bank->num_prot_blocks = SAMD_NUM_PROT_BLOCKS;
+       bank->prot_blocks = alloc_block_array(0, chip->prot_block_size, bank->num_prot_blocks);
+       if (!bank->prot_blocks)
+               return ERROR_FAIL;
 
        samd_protect_check(bank);
 
@@ -315,82 +494,70 @@ static int samd_probe(struct flash_bank *bank)
        return ERROR_OK;
 }
 
-static bool samd_check_error(struct target *target)
+static int samd_check_error(struct target *target)
 {
-       int ret;
-       bool error;
+       int ret, ret2;
        uint16_t status;
 
        ret = target_read_u16(target,
                        SAMD_NVMCTRL + SAMD_NVMCTRL_STATUS, &status);
        if (ret != ERROR_OK) {
                LOG_ERROR("Can't read NVM status");
-               return true;
+               return ret;
        }
 
-       if (status & 0x001C) {
-               if (status & (1 << 4)) /* NVME */
-                       LOG_ERROR("SAMD: NVM Error");
-               if (status & (1 << 3)) /* LOCKE */
-                       LOG_ERROR("SAMD: NVM lock error");
-               if (status & (1 << 2)) /* PROGE */
-                       LOG_ERROR("SAMD: NVM programming error");
+       if ((status & 0x001C) == 0)
+               return ERROR_OK;
 
-               error = true;
-       } else {
-               error = false;
+       if (status & (1 << 4)) { /* NVME */
+               LOG_ERROR("SAMD: NVM Error");
+               ret = ERROR_FLASH_OPERATION_FAILED;
+       }
+
+       if (status & (1 << 3)) { /* LOCKE */
+               LOG_ERROR("SAMD: NVM lock error");
+               ret = ERROR_FLASH_PROTECTED;
+       }
+
+       if (status & (1 << 2)) { /* PROGE */
+               LOG_ERROR("SAMD: NVM programming error");
+               ret = ERROR_FLASH_OPER_UNSUPPORTED;
        }
 
        /* Clear the error conditions by writing a one to them */
-       ret = target_write_u16(target,
+       ret2 = target_write_u16(target,
                        SAMD_NVMCTRL + SAMD_NVMCTRL_STATUS, status);
-       if (ret != ERROR_OK)
+       if (ret2 != ERROR_OK)
                LOG_ERROR("Can't clear NVM error conditions");
 
-       return error;
+       return ret;
 }
 
 static int samd_issue_nvmctrl_command(struct target *target, uint16_t cmd)
 {
+       int res;
+
        if (target->state != TARGET_HALTED) {
                LOG_ERROR("Target not halted");
                return ERROR_TARGET_NOT_HALTED;
        }
 
-       /* Read current configuration. */
-       uint16_t tmp = 0;
-       int res = target_read_u16(target, SAMD_NVMCTRL + SAMD_NVMCTRL_CTRLB,
-                       &tmp);
-       if (res != ERROR_OK)
-               return res;
-
-       /* Set cache disable. */
-       res = target_write_u16(target, SAMD_NVMCTRL + SAMD_NVMCTRL_CTRLB,
-                       tmp | (1<<18));
-       if (res != ERROR_OK)
-               return res;
-
        /* Issue the NVM command */
-       int res_cmd = target_write_u16(target,
+       res = target_write_u32(target,
                        SAMD_NVMCTRL + SAMD_NVMCTRL_CTRLA, SAMD_NVM_CMD(cmd));
-
-       /* Try to restore configuration, regardless of NVM command write
-        * status. */
-       res = target_write_u16(target, SAMD_NVMCTRL + SAMD_NVMCTRL_CTRLB, tmp);
-
-       if (res_cmd != ERROR_OK)
-               return res_cmd;
-
        if (res != ERROR_OK)
                return res;
 
        /* Check to see if the NVM command resulted in an error condition. */
-       if (samd_check_error(target))
-               return ERROR_FAIL;
-
-       return ERROR_OK;
+       return samd_check_error(target);
 }
 
+/**
+ * Erases a flash-row at the given address.
+ * @param target Pointer to the target structure.
+ * @param address The address of the row.
+ * @return On success ERROR_OK, on failure an errorcode.
+ */
 static int samd_erase_row(struct target *target, uint32_t address)
 {
        int res;
@@ -412,41 +579,61 @@ static int samd_erase_row(struct target *target, uint32_t address)
        return ERROR_OK;
 }
 
-static bool is_user_row_reserved_bit(uint8_t bit)
+/**
+ * Returns the bitmask of reserved bits in register.
+ * @param target Pointer to the target structure.
+ * @param mask Bitmask, 0 -> value stays untouched.
+ * @return On success ERROR_OK, on failure an errorcode.
+ */
+static int samd_get_reservedmask(struct target *target, uint64_t *mask)
 {
-       /* See Table 9-3 in the SAMD20 datasheet for more information. */
-       switch (bit) {
-               /* Reserved bits */
-               case 3:
-               case 7:
-               /* Voltage regulator internal configuration with default value of 0x70,
-                * may not be changed. */
-               case 17 ... 24:
-               /* 41 is voltage regulator internal configuration and must not be
-                * changed.  42 through 47 are reserved. */
-               case 41 ... 47:
-                       return true;
-               default:
-                       break;
+       int res;
+       /* Get the devicetype */
+       uint32_t id;
+       res = target_read_u32(target, SAMD_DSU + SAMD_DSU_DID, &id);
+       if (res != ERROR_OK) {
+               LOG_ERROR("Couldn't read Device ID register");
+               return res;
        }
-
-       return false;
+       const struct samd_family *family;
+       family = samd_find_family(id);
+       if (!family) {
+               LOG_ERROR("Couldn't determine device family");
+               return ERROR_FAIL;
+       }
+       *mask = family->nvm_userrow_res_mask;
+       return ERROR_OK;
 }
 
-/* Modify the contents of the User Row in Flash.  These are described in Table
- * 9-3 of the SAMD20 datasheet.  The User Row itself has a size of one page
- * and contains a combination of "fuses" and calibration data in bits 24:17.
- * We therefore try not to erase the row's contents unless we absolutely have
- * to and we don't permit modifying reserved bits. */
-static int samd_modify_user_row(struct target *target, uint32_t value,
-               uint8_t startb, uint8_t endb)
+static int read_userrow(struct target *target, uint64_t *userrow)
 {
        int res;
+       uint8_t buffer[8];
 
-       if (is_user_row_reserved_bit(startb) || is_user_row_reserved_bit(endb)) {
-               LOG_ERROR("Can't modify bits in the requested range");
-               return ERROR_FAIL;
-       }
+       res = target_read_memory(target, SAMD_USER_ROW, 4, 2, buffer);
+       if (res != ERROR_OK)
+               return res;
+
+       *userrow = target_buffer_get_u64(target, buffer);
+       return ERROR_OK;
+}
+
+/**
+ * Modify the contents of the User Row in Flash. The User Row itself
+ * has a size of one page and contains a combination of "fuses" and
+ * calibration data. Bits which have a value of zero in the mask will
+ * not be changed. Up to now devices only use the first 64 bits.
+ * @param target Pointer to the target structure.
+ * @param value_input The value to write.
+ * @param value_mask Bitmask, 0 -> value stays untouched.
+ * @return On success ERROR_OK, on failure an errorcode.
+ */
+static int samd_modify_user_row_masked(struct target *target,
+               uint64_t value_input, uint64_t value_mask)
+{
+       int res;
+       uint32_t nvm_ctrlb;
+       bool manual_wp = true;
 
        /* Retrieve the MCU's page size, in bytes. This is also the size of the
         * entire User Row. */
@@ -457,62 +644,82 @@ static int samd_modify_user_row(struct target *target, uint32_t value,
                return res;
        }
 
-       /* Make sure the size is sane before we allocate. */
-       assert(page_size > 0 && page_size <= SAMD_PAGE_SIZE_MAX);
-
-       /* Make sure we're within the single page that comprises the User Row. */
-       if (startb >= (page_size * 8) || endb >= (page_size * 8)) {
-               LOG_ERROR("Can't modify bits outside the User Row page range");
-               return ERROR_FAIL;
-       }
+       /* Make sure the size is sane. */
+       assert(page_size <= SAMD_PAGE_SIZE_MAX &&
+               page_size >= sizeof(value_input));
 
-       uint8_t *buf = malloc(page_size);
-       if (!buf)
-               return ERROR_FAIL;
+       uint8_t buf[SAMD_PAGE_SIZE_MAX];
+       /* Read the user row (comprising one page) by words. */
+       res = target_read_memory(target, SAMD_USER_ROW, 4, page_size / 4, buf);
+       if (res != ERROR_OK)
+               return res;
 
-       /* Read the user row (comprising one page) by half-words. */
-       res = target_read_memory(target, SAMD_USER_ROW, 2, page_size / 2, buf);
+       uint64_t value_device;
+       res = read_userrow(target, &value_device);
        if (res != ERROR_OK)
-               goto out_user_row;
+               return res;
+       uint64_t value_new = (value_input & value_mask) | (value_device & ~value_mask);
 
        /* We will need to erase before writing if the new value needs a '1' in any
         * position for which the current value had a '0'.  Otherwise we can avoid
         * erasing. */
-       uint32_t cur = buf_get_u32(buf, startb, endb - startb + 1);
-       if ((~cur) & value) {
+       if ((~value_device) & value_new) {
                res = samd_erase_row(target, SAMD_USER_ROW);
                if (res != ERROR_OK) {
                        LOG_ERROR("Couldn't erase user row");
-                       goto out_user_row;
+                       return res;
                }
        }
 
        /* Modify */
-       buf_set_u32(buf, startb, endb - startb + 1, value);
+       target_buffer_set_u64(target, buf, value_new);
 
-       /* Write the page buffer back out to the target.  A Flash write will be
-        * triggered automatically. */
+       /* Write the page buffer back out to the target. */
        res = target_write_memory(target, SAMD_USER_ROW, 4, page_size / 4, buf);
        if (res != ERROR_OK)
-               goto out_user_row;
+               return res;
 
-       if (samd_check_error(target)) {
-               res = ERROR_FAIL;
-               goto out_user_row;
+       /* Check if we need to do manual page write commands */
+       res = target_read_u32(target, SAMD_NVMCTRL + SAMD_NVMCTRL_CTRLB, &nvm_ctrlb);
+       if (res == ERROR_OK)
+               manual_wp = (nvm_ctrlb & SAMD_NVM_CTRLB_MANW) != 0;
+       else {
+               LOG_ERROR("Read of NVM register CTRKB failed.");
+               return ERROR_FAIL;
+       }
+       if (manual_wp) {
+               /* Trigger flash write */
+               res = samd_issue_nvmctrl_command(target, SAMD_NVM_CMD_WAP);
+       } else {
+               res = samd_check_error(target);
        }
 
-       /* Success */
-       res = ERROR_OK;
+       return res;
+}
 
-out_user_row:
-       free(buf);
+/**
+ * Modifies the user row register to the given value.
+ * @param target Pointer to the target structure.
+ * @param value The value to write.
+ * @param startb The bit-offset by which the given value is shifted.
+ * @param endb The bit-offset of the last bit in value to write.
+ * @return On success ERROR_OK, on failure an errorcode.
+ */
+static int samd_modify_user_row(struct target *target, uint64_t value,
+               uint8_t startb, uint8_t endb)
+{
+       uint64_t mask = 0;
+       int i;
+       for (i = startb ; i <= endb ; i++)
+               mask |= ((uint64_t)1) << i;
 
-       return res;
+       return samd_modify_user_row_masked(target, value << startb, mask);
 }
 
-static int samd_protect(struct flash_bank *bank, int set, int first, int last)
+static int samd_protect(struct flash_bank *bank, int set,
+               unsigned int first, unsigned int last)
 {
-       struct samd_info *chip = (struct samd_info *)bank->driver_priv;
+       int res = ERROR_OK;
 
        /* We can issue lock/unlock region commands with the target running but
         * the settings won't persist unless we're able to modify the LOCK regions
@@ -522,18 +729,16 @@ static int samd_protect(struct flash_bank *bank, int set, int first, int last)
                return ERROR_TARGET_NOT_HALTED;
        }
 
-       int res = ERROR_OK;
-
-       for (int s = first; s <= last; s++) {
-               if (set != bank->sectors[s].is_protected) {
-                       /* Load an address that is within this sector (we use offset 0) */
+       for (unsigned int prot_block = first; prot_block <= last; prot_block++) {
+               if (set != bank->prot_blocks[prot_block].is_protected) {
+                       /* Load an address that is within this protection block (we use offset 0) */
                        res = target_write_u32(bank->target,
                                                        SAMD_NVMCTRL + SAMD_NVMCTRL_ADDR,
-                                                       ((s * chip->sector_size) >> 1));
+                                                       bank->prot_blocks[prot_block].offset >> 1);
                        if (res != ERROR_OK)
                                goto exit;
 
-                       /* Tell the controller to lock that sector */
+                       /* Tell the controller to lock that block */
                        res = samd_issue_nvmctrl_command(bank->target,
                                        set ? SAMD_NVM_CMD_LR : SAMD_NVM_CMD_UR);
                        if (res != ERROR_OK)
@@ -543,11 +748,12 @@ static int samd_protect(struct flash_bank *bank, int set, int first, int last)
 
        /* We've now applied our changes, however they will be undone by the next
         * reset unless we also apply them to the LOCK bits in the User Page.  The
-        * LOCK bits start at bit 48, correspoding to Sector 0 and end with bit 63,
+        * LOCK bits start at bit 48, corresponding to Sector 0 and end with bit 63,
         * corresponding to Sector 15.  A '1' means unlocked and a '0' means
         * locked.  See Table 9-3 in the SAMD20 datasheet for more details. */
 
-       res = samd_modify_user_row(bank->target, set ? 0x0000 : 0xFFFF,
+       res = samd_modify_user_row(bank->target,
+                       set ? (uint64_t)0 : (uint64_t)UINT64_MAX,
                        48 + first, 48 + last);
        if (res != ERROR_OK)
                LOG_WARNING("SAMD: protect settings were not made persistent!");
@@ -560,10 +766,10 @@ exit:
        return res;
 }
 
-static int samd_erase(struct flash_bank *bank, int first, int last)
+static int samd_erase(struct flash_bank *bank, unsigned int first,
+               unsigned int last)
 {
        int res;
-       int rows_in_sector;
        struct samd_info *chip = (struct samd_info *)bank->driver_priv;
 
        if (bank->target->state != TARGET_HALTED) {
@@ -577,145 +783,34 @@ static int samd_erase(struct flash_bank *bank, int first, int last)
                        return ERROR_FLASH_BANK_NOT_PROBED;
        }
 
-       /* The SAMD NVM has row erase granularity.  There are four pages in a row
-        * and the number of rows in a sector depends on the sector size, which in
-        * turn depends on the Flash capacity as there is a fixed number of
-        * sectors. */
-       rows_in_sector = chip->sector_size / (chip->page_size * 4);
-
        /* For each sector to be erased */
-       for (int s = first; s <= last; s++) {
-               if (bank->sectors[s].is_protected) {
-                       LOG_ERROR("SAMD: failed to erase sector %d. That sector is write-protected", s);
-                       return ERROR_FLASH_OPERATION_FAILED;
-               }
-
-               if (!bank->sectors[s].is_erased) {
-                       /* For each row in that sector */
-                       for (int r = s * rows_in_sector; r < (s + 1) * rows_in_sector; r++) {
-                               res = samd_erase_row(bank->target, r * chip->page_size * 4);
-                               if (res != ERROR_OK) {
-                                       LOG_ERROR("SAMD: failed to erase sector %d", s);
-                                       return res;
-                               }
-                       }
-
-                       bank->sectors[s].is_erased = 1;
-               }
-       }
-
-       return ERROR_OK;
-}
-
-static struct flash_sector *samd_find_sector_by_address(struct flash_bank *bank, uint32_t address)
-{
-       struct samd_info *chip = (struct samd_info *)bank->driver_priv;
-
-       for (int i = 0; i < bank->num_sectors; i++) {
-               if (bank->sectors[i].offset <= address &&
-                   address < bank->sectors[i].offset + chip->sector_size)
-                       return &bank->sectors[i];
-       }
-       return NULL;
-}
-
-/* Write an entire row (four pages) from host buffer 'buf' to row-aligned
- * 'address' in the Flash. */
-static int samd_write_row(struct flash_bank *bank, uint32_t address,
-               const uint8_t *buf)
-{
-       int res;
-       struct samd_info *chip = (struct samd_info *)bank->driver_priv;
-
-       struct flash_sector *sector = samd_find_sector_by_address(bank, address);
-
-       if (!sector) {
-               LOG_ERROR("Can't find sector corresponding to address 0x%08" PRIx32, address);
-               return ERROR_FLASH_OPERATION_FAILED;
-       }
-
-       if (sector->is_protected) {
-               LOG_ERROR("Trying to write to a protected sector at 0x%08" PRIx32, address);
-               return ERROR_FLASH_OPERATION_FAILED;
-       }
-
-       /* Erase the row that we'll be writing to */
-       res = samd_erase_row(bank->target, address);
-       if (res != ERROR_OK)
-               return res;
-
-       /* Now write the pages in this row. */
-       for (unsigned int i = 0; i < 4; i++) {
-               bool error;
-
-               /* Write the page contents to the target's page buffer.  A page write
-                * is issued automatically once the last location is written in the
-                * page buffer (ie: a complete page has been written out). */
-               res = target_write_memory(bank->target, address, 4,
-                               chip->page_size / 4, buf);
+       for (unsigned int s = first; s <= last; s++) {
+               res = samd_erase_row(bank->target, bank->sectors[s].offset);
                if (res != ERROR_OK) {
-                       LOG_ERROR("%s: %d", __func__, __LINE__);
+                       LOG_ERROR("SAMD: failed to erase sector %d at 0x%08" PRIx32, s, bank->sectors[s].offset);
                        return res;
                }
-
-               error = samd_check_error(bank->target);
-               if (error)
-                       return ERROR_FAIL;
-
-               /* Next page */
-               address += chip->page_size;
-               buf += chip->page_size;
        }
 
-       sector->is_erased = 0;
-
-       return res;
+       return ERROR_OK;
 }
 
-/* Write partial contents into row-aligned 'address' on the Flash from host
- * buffer 'buf' by writing 'nb' of 'buf' at 'row_offset' into the Flash row. */
-static int samd_write_row_partial(struct flash_bank *bank, uint32_t address,
-               const uint8_t *buf, uint32_t row_offset, uint32_t nb)
-{
-       int res;
-       struct samd_info *chip = (struct samd_info *)bank->driver_priv;
-       uint32_t row_size = chip->page_size * 4;
-       uint8_t *rb = malloc(row_size);
-       if (!rb)
-               return ERROR_FAIL;
-
-       assert(row_offset + nb < row_size);
-       assert((address % row_size) == 0);
-
-       /* Retrieve the full row contents from Flash */
-       res = target_read_memory(bank->target, address, 4, row_size / 4, rb);
-       if (res != ERROR_OK) {
-               free(rb);
-               return res;
-       }
-
-       /* Insert our partial row over the data from Flash */
-       memcpy(rb + (row_offset % row_size), buf, nb);
-
-       /* Write the row back out */
-       res = samd_write_row(bank, address, rb);
-       free(rb);
-
-       return res;
-}
 
 static int samd_write(struct flash_bank *bank, const uint8_t *buffer,
                uint32_t offset, uint32_t count)
 {
        int res;
+       uint32_t nvm_ctrlb;
        uint32_t address;
-       uint32_t nb = 0;
+       uint32_t pg_offset;
+       uint32_t nb;
+       uint32_t nw;
        struct samd_info *chip = (struct samd_info *)bank->driver_priv;
-       uint32_t row_size = chip->page_size * 4;
+       uint8_t *pb = NULL;
+       bool manual_wp;
 
        if (bank->target->state != TARGET_HALTED) {
                LOG_ERROR("Target not halted");
-
                return ERROR_TARGET_NOT_HALTED;
        }
 
@@ -724,119 +819,142 @@ static int samd_write(struct flash_bank *bank, const uint8_t *buffer,
                        return ERROR_FLASH_BANK_NOT_PROBED;
        }
 
-       if (offset % row_size) {
-               /* We're starting at an unaligned offset so we'll write a partial row
-                * comprising that offset and up to the end of that row. */
-               nb = row_size - (offset % row_size);
-               if (nb > count)
-                       nb = count;
-       } else if (count < row_size) {
-               /* We're writing an aligned but partial row. */
-               nb = count;
-       }
+       /* Check if we need to do manual page write commands */
+       res = target_read_u32(bank->target, SAMD_NVMCTRL + SAMD_NVMCTRL_CTRLB, &nvm_ctrlb);
 
-       address = (offset / row_size) * row_size + bank->base;
+       if (res != ERROR_OK)
+               return res;
 
-       if (nb > 0) {
-               res = samd_write_row_partial(bank, address, buffer,
-                               offset % row_size, nb);
-               if (res != ERROR_OK)
-                       return res;
+       if (nvm_ctrlb & SAMD_NVM_CTRLB_MANW)
+               manual_wp = true;
+       else
+               manual_wp = false;
 
-               /* We're done with the row contents */
-               count -= nb;
-               offset += nb;
-               buffer += row_size;
+       res = samd_issue_nvmctrl_command(bank->target, SAMD_NVM_CMD_PBC);
+       if (res != ERROR_OK) {
+               LOG_ERROR("%s: %d", __func__, __LINE__);
+               return res;
        }
 
-       /* There's at least one aligned row to write out. */
-       if (count >= row_size) {
-               int nr = count / row_size + ((count % row_size) ? 1 : 0);
-               unsigned int r = 0;
-
-               for (unsigned int i = address / row_size;
-                               (i < (address / row_size) + nr) && count > 0; i++) {
-                       address = (i * row_size) + bank->base;
-
-                       if (count >= row_size) {
-                               res = samd_write_row(bank, address, buffer + (r * row_size));
-                               /* Advance one row */
-                               offset += row_size;
-                               count -= row_size;
-                       } else {
-                               res = samd_write_row_partial(bank, address,
-                                               buffer + (r * row_size), 0, count);
-                               /* We're done after this. */
-                               offset += count;
-                               count = 0;
+       while (count) {
+               nb = chip->page_size - offset % chip->page_size;
+               if (count < nb)
+                       nb = count;
+
+               address = bank->base + offset;
+               pg_offset = offset % chip->page_size;
+
+               if (offset % 4 || (offset + nb) % 4) {
+                       /* Either start or end of write is not word aligned */
+                       if (!pb) {
+                               pb = malloc(chip->page_size);
+                               if (!pb)
+                                       return ERROR_FAIL;
                        }
 
-                       r++;
+                       /* Set temporary page buffer to 0xff and overwrite the relevant part */
+                       memset(pb, 0xff, chip->page_size);
+                       memcpy(pb + pg_offset, buffer, nb);
 
-                       if (res != ERROR_OK)
-                               return res;
-               }
-       }
+                       /* Align start address to a word boundary */
+                       address -= offset % 4;
+                       pg_offset -= offset % 4;
+                       assert(pg_offset % 4 == 0);
 
-       return ERROR_OK;
-}
+                       /* Extend length to whole words */
+                       nw = (nb + offset % 4 + 3) / 4;
+                       assert(pg_offset + 4 * nw <= chip->page_size);
 
-FLASH_BANK_COMMAND_HANDLER(samd_flash_bank_command)
-{
-       struct samd_info *chip = samd_chips;
+                       /* Now we have original data extended by 0xff bytes
+                        * to the nearest word boundary on both start and end */
+                       res = target_write_memory(bank->target, address, 4, nw, pb + pg_offset);
+               } else {
+                       assert(nb % 4 == 0);
+                       nw = nb / 4;
+                       assert(pg_offset + 4 * nw <= chip->page_size);
 
-       while (chip) {
-               if (chip->target == bank->target)
-                       break;
-               chip = chip->next;
-       }
+                       /* Word aligned data, use direct write from buffer */
+                       res = target_write_memory(bank->target, address, 4, nw, buffer);
+               }
+               if (res != ERROR_OK) {
+                       LOG_ERROR("%s: %d", __func__, __LINE__);
+                       goto free_pb;
+               }
 
-       if (!chip) {
-               /* Create a new chip */
-               chip = calloc(1, sizeof(*chip));
-               if (!chip)
-                       return ERROR_FAIL;
+               /* Devices with errata 13134 have automatic page write enabled by default
+                * For other devices issue a write page CMD to the NVM
+                * If the page has not been written up to the last word
+                * then issue CMD_WP always */
+               if (manual_wp || pg_offset + 4 * nw < chip->page_size) {
+                       res = samd_issue_nvmctrl_command(bank->target, SAMD_NVM_CMD_WP);
+               } else {
+                       /* Access through AHB is stalled while flash is being programmed */
+                       usleep(200);
 
-               chip->target = bank->target;
-               chip->probed = false;
+                       res = samd_check_error(bank->target);
+               }
 
-               bank->driver_priv = chip;
+               if (res != ERROR_OK) {
+                       LOG_ERROR("%s: write failed at address 0x%08" PRIx32, __func__, address);
+                       goto free_pb;
+               }
 
-               /* Insert it into the chips list (at head) */
-               chip->next = samd_chips;
-               samd_chips = chip;
+               /* We're done with the page contents */
+               count -= nb;
+               offset += nb;
+               buffer += nb;
        }
 
+free_pb:
+       free(pb);
+       return res;
+}
+
+FLASH_BANK_COMMAND_HANDLER(samd_flash_bank_command)
+{
        if (bank->base != SAMD_FLASH) {
-               LOG_ERROR("Address 0x%08" PRIx32 " invalid bank address (try 0x%08" PRIx32
+               LOG_ERROR("Address " TARGET_ADDR_FMT
+                               " invalid bank address (try 0x%08" PRIx32
                                "[at91samd series] )",
                                bank->base, SAMD_FLASH);
                return ERROR_FAIL;
        }
 
-       return ERROR_OK;
-}
+       struct samd_info *chip;
+       chip = calloc(1, sizeof(*chip));
+       if (!chip) {
+               LOG_ERROR("No memory for flash bank chip info");
+               return ERROR_FAIL;
+       }
+
+       chip->target = bank->target;
+       chip->probed = false;
+
+       bank->driver_priv = chip;
 
-COMMAND_HANDLER(samd_handle_info_command)
-{
        return ERROR_OK;
 }
 
 COMMAND_HANDLER(samd_handle_chip_erase_command)
 {
        struct target *target = get_current_target(CMD_CTX);
+       int res = ERROR_FAIL;
 
        if (target) {
                /* Enable access to the DSU by disabling the write protect bit */
                target_write_u32(target, SAMD_PAC1, (1<<1));
+               /* intentionally without error checking - not accessible on secured chip */
+
                /* Tell the DSU to perform a full chip erase.  It takes about 240ms to
                 * perform the erase. */
-               target_write_u8(target, SAMD_DSU, (1<<4));
-
-               command_print(CMD_CTX, "chip erased");
+               res = target_write_u8(target, SAMD_DSU + SAMD_DSU_CTRL_EXT, (1<<4));
+               if (res == ERROR_OK)
+                       command_print(CMD, "chip erase started");
+               else
+                       command_print(CMD, "write to DSU CTRL failed");
        }
 
-       return ERROR_OK;
+       return res;
 }
 
 COMMAND_HANDLER(samd_handle_set_security_command)
@@ -845,7 +963,7 @@ COMMAND_HANDLER(samd_handle_set_security_command)
        struct target *target = get_current_target(CMD_CTX);
 
        if (CMD_ARGC < 1 || (CMD_ARGC >= 1 && (strcmp(CMD_ARGV[0], "enable")))) {
-               command_print(CMD_CTX, "supply the \"enable\" argument to proceed.");
+               command_print(CMD, "supply the \"enable\" argument to proceed.");
                return ERROR_COMMAND_SYNTAX_ERROR;
        }
 
@@ -859,9 +977,9 @@ COMMAND_HANDLER(samd_handle_set_security_command)
 
                /* Check (and clear) error conditions */
                if (res == ERROR_OK)
-                       command_print(CMD_CTX, "chip secured on next power-cycle");
+                       command_print(CMD, "chip secured on next power-cycle");
                else
-                       command_print(CMD_CTX, "failed to secure chip");
+                       command_print(CMD, "failed to secure chip");
        }
 
        return res;
@@ -892,7 +1010,7 @@ COMMAND_HANDLER(samd_handle_eeprom_command)
                                }
 
                                if (code > 6) {
-                                       command_print(CMD_CTX, "Invalid EEPROM size.  Please see "
+                                       command_print(CMD, "Invalid EEPROM size.  Please see "
                                                        "datasheet for a list valid sizes.");
                                        return ERROR_COMMAND_SYNTAX_ERROR;
                                }
@@ -906,10 +1024,10 @@ COMMAND_HANDLER(samd_handle_eeprom_command)
                                uint32_t size = ((val >> 4) & 0x7); /* grab size code */
 
                                if (size == 0x7)
-                                       command_print(CMD_CTX, "EEPROM is disabled");
+                                       command_print(CMD, "EEPROM is disabled");
                                else {
                                        /* Otherwise, 6 is 256B, 0 is 16KB */
-                                       command_print(CMD_CTX, "EEPROM size is %u bytes",
+                                       command_print(CMD, "EEPROM size is %u bytes",
                                                        (2 << (13 - size)));
                                }
                        }
@@ -919,6 +1037,56 @@ COMMAND_HANDLER(samd_handle_eeprom_command)
        return res;
 }
 
+COMMAND_HANDLER(samd_handle_nvmuserrow_command)
+{
+       int res = ERROR_OK;
+       struct target *target = get_current_target(CMD_CTX);
+
+       if (target) {
+               if (CMD_ARGC > 2) {
+                       command_print(CMD, "Too much Arguments given.");
+                       return ERROR_COMMAND_SYNTAX_ERROR;
+               }
+
+               if (CMD_ARGC > 0) {
+                       if (target->state != TARGET_HALTED) {
+                               LOG_ERROR("Target not halted.");
+                               return ERROR_TARGET_NOT_HALTED;
+                       }
+
+                       uint64_t mask;
+                       res = samd_get_reservedmask(target, &mask);
+                       if (res != ERROR_OK) {
+                               LOG_ERROR("Couldn't determine the mask for reserved bits.");
+                               return ERROR_FAIL;
+                       }
+                       mask &= NVMUSERROW_LOCKBIT_MASK;
+
+                       uint64_t value;
+                       COMMAND_PARSE_NUMBER(u64, CMD_ARGV[0], value);
+
+                       if (CMD_ARGC == 2) {
+                               uint64_t mask_temp;
+                               COMMAND_PARSE_NUMBER(u64, CMD_ARGV[1], mask_temp);
+
+                               mask &= mask_temp;
+                       }
+                       res = samd_modify_user_row_masked(target, value, mask);
+                       if (res != ERROR_OK)
+                               return res;
+               }
+
+               /* read register */
+               uint64_t value;
+               res = read_userrow(target, &value);
+               if (res == ERROR_OK)
+                       command_print(CMD, "NVMUSERROW: 0x%016"PRIX64, value);
+               else
+                       LOG_ERROR("NVMUSERROW could not be read.");
+       }
+       return res;
+}
+
 COMMAND_HANDLER(samd_handle_bootloader_command)
 {
        int res = ERROR_OK;
@@ -952,7 +1120,7 @@ COMMAND_HANDLER(samd_handle_bootloader_command)
                                }
 
                                if (code > 6) {
-                                       command_print(CMD_CTX, "Invalid bootloader size.  Please "
+                                       command_print(CMD, "Invalid bootloader size.  Please "
                                                        "see datasheet for a list valid sizes.");
                                        return ERROR_COMMAND_SYNTAX_ERROR;
                                }
@@ -973,8 +1141,8 @@ COMMAND_HANDLER(samd_handle_bootloader_command)
                                        nb = (2 << (8 - size)) * page_size;
 
                                /* There are 4 pages per row */
-                               command_print(CMD_CTX, "Bootloader size is %u bytes (%u rows)",
-                                          nb, nb / (page_size * 4));
+                               command_print(CMD, "Bootloader size is %" PRIu32 " bytes (%" PRIu32 " rows)",
+                                          nb, (uint32_t)(nb / (page_size * 4)));
                        }
                }
        }
@@ -982,38 +1150,77 @@ COMMAND_HANDLER(samd_handle_bootloader_command)
        return res;
 }
 
+
+
+COMMAND_HANDLER(samd_handle_reset_deassert)
+{
+       struct target *target = get_current_target(CMD_CTX);
+       int retval = ERROR_OK;
+       enum reset_types jtag_reset_config = jtag_get_reset_config();
+
+       /* If the target has been unresponsive before, try to re-establish
+        * communication now - CPU is held in reset by DSU, DAP is working */
+       if (!target_was_examined(target))
+               target_examine_one(target);
+       target_poll(target);
+
+       /* In case of sysresetreq, debug retains state set in cortex_m_assert_reset()
+        * so we just release reset held by DSU
+        *
+        * n_RESET (srst) clears the DP, so reenable debug and set vector catch here
+        *
+        * After vectreset DSU release is not needed however makes no harm
+        */
+       if (target->reset_halt && (jtag_reset_config & RESET_HAS_SRST)) {
+               retval = target_write_u32(target, DCB_DHCSR, DBGKEY | C_HALT | C_DEBUGEN);
+               if (retval == ERROR_OK)
+                       retval = target_write_u32(target, DCB_DEMCR,
+                               TRCENA | VC_HARDERR | VC_BUSERR | VC_CORERESET);
+               /* do not return on error here, releasing DSU reset is more important */
+       }
+
+       /* clear CPU Reset Phase Extension bit */
+       int retval2 = target_write_u8(target, SAMD_DSU + SAMD_DSU_STATUSA, (1<<1));
+       if (retval2 != ERROR_OK)
+               return retval2;
+
+       return retval;
+}
+
 static const struct command_registration at91samd_exec_command_handlers[] = {
        {
-               .name = "info",
-               .handler = samd_handle_info_command,
+               .name = "dsu_reset_deassert",
+               .handler = samd_handle_reset_deassert,
                .mode = COMMAND_EXEC,
-               .help = "Print information about the current at91samd chip"
-                       "and its flash configuration.",
+               .help = "Deassert internal reset held by DSU.",
+               .usage = "",
        },
        {
                .name = "chip-erase",
                .handler = samd_handle_chip_erase_command,
                .mode = COMMAND_EXEC,
-               .help = "Erase the entire Flash by using the Chip"
+               .help = "Erase the entire Flash by using the Chip-"
                        "Erase feature in the Device Service Unit (DSU).",
+               .usage = "",
        },
        {
                .name = "set-security",
                .handler = samd_handle_set_security_command,
                .mode = COMMAND_EXEC,
-               .help = "Secure the chip's Flash by setting the Security Bit."
-                       "This makes it impossible to read the Flash contents."
-                       "The only way to undo this is to issue the chip-erase"
+               .help = "Secure the chip's Flash by setting the Security Bit. "
+                       "This makes it impossible to read the Flash contents. "
+                       "The only way to undo this is to issue the chip-erase "
                        "command.",
+               .usage = "'enable'",
        },
        {
                .name = "eeprom",
                .usage = "[size_in_bytes]",
                .handler = samd_handle_eeprom_command,
                .mode = COMMAND_EXEC,
-               .help = "Show or set the EEPROM size setting, stored in the User Row."
-                       "Please see Table 20-3 of the SAMD20 datasheet for allowed values."
-                       "Changes are stored immediately but take affect after the MCU is"
+               .help = "Show or set the EEPROM size setting, stored in the User Row. "
+                       "Please see Table 20-3 of the SAMD20 datasheet for allowed values. "
+                       "Changes are stored immediately but take affect after the MCU is "
                        "reset.",
        },
        {
@@ -1021,11 +1228,22 @@ static const struct command_registration at91samd_exec_command_handlers[] = {
                .usage = "[size_in_bytes]",
                .handler = samd_handle_bootloader_command,
                .mode = COMMAND_EXEC,
-               .help = "Show or set the bootloader size, stored in the User Row."
-                       "Please see Table 20-2 of the SAMD20 datasheet for allowed values."
-                       "Changes are stored immediately but take affect after the MCU is"
+               .help = "Show or set the bootloader size, stored in the User Row. "
+                       "Please see Table 20-2 of the SAMD20 datasheet for allowed values. "
+                       "Changes are stored immediately but take affect after the MCU is "
                        "reset.",
        },
+       {
+               .name = "nvmuserrow",
+               .usage = "[value] [mask]",
+               .handler = samd_handle_nvmuserrow_command,
+               .mode = COMMAND_EXEC,
+               .help = "Show or set the nvmuserrow register. It is 64 bit wide "
+                       "and located at address 0x804000. Use the optional mask argument "
+                       "to prevent changes at positions where the bitvalue is zero. "
+                       "For security reasons the lock- and reserved-bits are masked out "
+                       "in background and therefore cannot be changed.",
+       },
        COMMAND_REGISTRATION_DONE
 };
 
@@ -1040,7 +1258,7 @@ static const struct command_registration at91samd_command_handlers[] = {
        COMMAND_REGISTRATION_DONE
 };
 
-struct flash_driver at91samd_flash = {
+const struct flash_driver at91samd_flash = {
        .name = "at91samd",
        .commands = at91samd_command_handlers,
        .flash_bank_command = samd_flash_bank_command,
@@ -1052,4 +1270,5 @@ struct flash_driver at91samd_flash = {
        .auto_probe = samd_probe,
        .erase_check = default_flash_blank_check,
        .protect_check = samd_protect_check,
+       .free_driver_priv = default_flash_free_driver_priv,
 };