Add the support for "flush_buffer" ops in order to flush any write buffers,
reset any DMA state and stop any ongoing DMA transfers when the
port->state->xmit circular buffer is cleared.
Signed-off-by: Erwan Le Ray <erwan.leray@xxxxxxxxxxx>
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 99dfa884cbef..9db6708e3d9f 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -597,6 +597,19 @@ static void stm32_usart_start_tx(struct uart_port *port)
stm32_usart_transmit_chars(port);
}
+/* Flush the transmit buffer. */
+static void stm32_usart_flush_buffer(struct uart_port *port)
+{
+ struct stm32_port *stm32_port = to_stm32_port(port);
+ const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
+
+ if (stm32_port->tx_ch) {
+ dmaengine_terminate_async(stm32_port->tx_ch);
+ stm32_usart_clr_bits(port, ofs->cr3, USART_CR3_DMAT);
+ stm32_port->tx_dma_busy = false;
+ }
+}
+
/* Throttle the remote when input buffer is about to overflow. */
static void stm32_usart_throttle(struct uart_port *port)
{
@@ -992,6 +1005,7 @@ static const struct uart_ops stm32_uart_ops = {
.break_ctl = stm32_usart_break_ctl,
.startup = stm32_usart_startup,
.shutdown = stm32_usart_shutdown,
+ .flush_buffer = stm32_usart_flush_buffer,
.set_termios = stm32_usart_set_termios,
.pm = stm32_usart_pm,
.type = stm32_usart_type,
--
2.17.1
