altos: Use TXE instead of TC for serial on STM32l

Using TXE allows for full-speed communication, rather than waiting for
each byte to be transmitted before inserting the next into the queue.

Signed-off-by: Keith Packard <keithp@keithp.com>

diff --git a/src/stm/ao_arch_funcs.h b/src/stm/ao_arch_funcs.h
index f1d17ed152a5a8e0aea983e3446dcc1018634b72..6fcfd5f85a1187e5e3018dd1827ef2e7e507acb4 100644 (file)
--- a/src/stm/ao_arch_funcs.h
+++ b/src/stm/ao_arch_funcs.h
@@ -284,6 +284,8 @@ struct ao_stm_usart {
        struct ao_fifo          tx_fifo;
        struct stm_usart        *reg;
        uint8_t                 tx_started;
+       uint8_t                 tx_running;
+       uint8_t                 draining;
 };
 
 #if HAS_SERIAL_1

diff --git a/src/stm/ao_serial_stm.c b/src/stm/ao_serial_stm.c
index 9959e460771d6fb67d0318e333aaca961cdfb036..e7b6ab78d71acfa79b3724c0e8379825b337e312 100644 (file)
--- a/src/stm/ao_serial_stm.c
+++ b/src/stm/ao_serial_stm.c
@@ -26,14 +26,19 @@ ao_debug_out(char c)
        stm_usart1.dr = c;
 }
 
-static void
+static int
 _ao_usart_tx_start(struct ao_stm_usart *usart)
 {
        if (!ao_fifo_empty(usart->tx_fifo) && !usart->tx_started)
        {
                usart->tx_started = 1;
+               usart->tx_running = 1;
+               usart->reg->cr1 |= (1 << STM_USART_CR1_TXEIE) | (1 << STM_USART_CR1_TCIE);
                ao_fifo_remove(usart->tx_fifo, usart->reg->dr);
+               ao_wakeup(&usart->tx_fifo);
+               return 1;
        }
+       return 0;
 }
 
 static void
@@ -52,10 +57,18 @@ ao_usart_isr(struct ao_stm_usart *usart, int stdin)
                if (stdin)
                        ao_wakeup(&ao_stdin_ready);
        }
-       if (sr & (1 << STM_USART_SR_TC)) {
+       if (sr & (1 << STM_USART_SR_TXE)) {
                usart->tx_started = 0;
-               _ao_usart_tx_start(usart);
-               ao_wakeup(&usart->tx_fifo);
+               if (!_ao_usart_tx_start(usart))
+                       usart->reg->cr1 &= ~(1<< STM_USART_CR1_TXEIE);
+       }
+       if (sr & (1 << STM_USART_SR_TC)) {
+               usart->tx_running = 0;
+               usart->reg->cr1 &= ~(1 << STM_USART_CR1_TCIE);
+               if (usart->draining) {
+                       usart->draining = 0;
+                       ao_wakeup(&usart->tx_fifo);
+               }
        }
 }
 
@@ -105,12 +118,14 @@ ao_usart_putchar(struct ao_stm_usart *usart, char c)
        ao_arch_release_interrupts();
 }
 
-void
+static void
 ao_usart_drain(struct ao_stm_usart *usart)
 {
        ao_arch_block_interrupts();
-       while (!ao_fifo_empty(usart->tx_fifo))
+       while (!ao_fifo_empty(usart->tx_fifo) || usart->tx_running) {
+               usart->draining = 1;
                ao_sleep(&usart->tx_fifo);
+       }
        ao_arch_release_interrupts();
 }
 
@@ -153,7 +168,7 @@ ao_usart_init(struct ao_stm_usart *usart)
                          (0 << STM_USART_CR1_PS) |
                          (0 << STM_USART_CR1_PEIE) |
                          (0 << STM_USART_CR1_TXEIE) |
-                         (1 << STM_USART_CR1_TCIE) |
+                         (0 << STM_USART_CR1_TCIE) |
                          (1 << STM_USART_CR1_RXNEIE) |
                          (0 << STM_USART_CR1_IDLEIE) |
                          (1 << STM_USART_CR1_TE) |
@@ -234,6 +249,7 @@ ao_serial1_drain(void)
 void
 ao_serial1_set_speed(uint8_t speed)
 {
+       ao_usart_drain(&ao_stm_usart1);
        ao_usart_set_speed(&ao_stm_usart1, speed);
 }
 #endif /* HAS_SERIAL_1 */
@@ -277,6 +293,7 @@ ao_serial2_drain(void)
 void
 ao_serial2_set_speed(uint8_t speed)
 {
+       ao_usart_drain(&ao_stm_usart2);
        ao_usart_set_speed(&ao_stm_usart2, speed);
 }
 #endif /* HAS_SERIAL_2 */
@@ -314,8 +331,15 @@ _ao_serial3_sleep_for(uint16_t timeout)
 void
 ao_serial3_set_speed(uint8_t speed)
 {
+       ao_usart_drain(&ao_stm_usart3);
        ao_usart_set_speed(&ao_stm_usart3, speed);
 }
+
+void
+ao_serial3_drain(void)
+{
+       ao_usart_drain(&ao_stm_usart3);
+}
 #endif /* HAS_SERIAL_3 */
 
 void