samd21: Leave serial RX interrupts enabled

Just discard characters in the ISR. This avoids complex management of
the enable bit.

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

diff --git a/src/samd21/ao_serial_samd21.c b/src/samd21/ao_serial_samd21.c
index 504dd49055f57869136279c2e4a186e592130a7a..97d8379083ce9c529efe3977f8c076f5a0c15324 100644 (file)
--- a/src/samd21/ao_serial_samd21.c
+++ b/src/samd21/ao_serial_samd21.c
@@ -40,8 +40,9 @@ static void
 _ao_usart_rx(struct ao_samd21_usart *usart, int is_stdin)
 {
        if (usart->reg->intflag & (1 << SAMD21_SERCOM_INTFLAG_RXC)) {
+               uint8_t data = (uint8_t) usart->reg->data;
                if (!ao_fifo_full(usart->rx_fifo)) {
-                       ao_fifo_insert(usart->rx_fifo, usart->reg->data);
+                       ao_fifo_insert(usart->rx_fifo, data);
                        ao_wakeup(&usart->rx_fifo);
                        if (is_stdin)
                                ao_wakeup(&ao_stdin_ready);
@@ -54,8 +55,6 @@ _ao_usart_rx(struct ao_samd21_usart *usart, int is_stdin)
                                usart->rts = 0;
                        }
 #endif
-               } else {
-                       usart->reg->intenclr = (1 << SAMD21_SERCOM_INTFLAG_RXC);
                }
        }
 }
@@ -157,11 +156,12 @@ ao_usart_init(struct ao_samd21_usart *usart, bool hw_flow, uint8_t id, uint8_t t
                      (0 << SAMD21_SERCOM_CTRLA_CPOL) |
                      (1 << SAMD21_SERCOM_CTRLA_DORD)); /* LSB first */
 
+       /* Enable receive interrupt */
+       reg->intenset = (1 << SAMD21_SERCOM_INTFLAG_RXC);
+
        while (reg->syncbusy & (1 << SAMD21_SERCOM_SYNCBUSY_ENABLE))
                ;
 
-       /* Enable receive interrupt */
-       reg->intenset = (1 << SAMD21_SERCOM_INTFLAG_RXC);
 }
 
 static int
@@ -174,10 +174,6 @@ _ao_usart_pollchar(struct ao_samd21_usart *usart)
        else {
                uint8_t u;
                ao_fifo_remove(usart->rx_fifo, u);
-               if ((usart->reg->intenset & (1 << SAMD21_SERCOM_INTFLAG_RXC)) == 0) {
-                       if (ao_fifo_barely(usart->rx_fifo))
-                               usart->reg->intenset = (1 << SAMD21_SERCOM_INTFLAG_RXC);
-               }
 #if HAS_SERIAL_SW_FLOW
                /* If we've cleared RTS, check if there's space now and turn it back on */
                if (usart->gpio_rts && usart->rts == 0 && ao_fifo_barely(usart->rx_fifo)) {
@@ -312,6 +308,13 @@ ao_serial_init(void)
        samd21_port_pmux_set(&samd21_port_a, 11, SAMD21_PORT_PMUX_FUNC_C);
        txpo = SAMD21_SERCOM_CTRLA_TXPO_TX_2; /* pad 2 */
        rxpo = SAMD21_SERCOM_CTRLA_RXPO_RX_3; /* pad 3 */
+#elif SERIAL_0_PA08_PA09
+       /* Pin settings */
+       ao_enable_port(&samd21_port_a);
+       samd21_port_pmux_set(&samd21_port_a, 8, SAMD21_PORT_PMUX_FUNC_C);
+       samd21_port_pmux_set(&samd21_port_a, 9, SAMD21_PORT_PMUX_FUNC_C);
+       txpo = SAMD21_SERCOM_CTRLA_TXPO_TX_0; /* pad 0 */
+       rxpo = SAMD21_SERCOM_CTRLA_RXPO_RX_1; /* pad 1 */
 #else
 #error "No SERIAL_0 port configuration specified"
 #endif