From: Amelie Delaunay <amelie.delaunay@foss.st.com>

In shutdown, RX DMA channel is terminated. If the DMA RX callback is
scheduled but not yet executed, while a new RX DMA transfer is started, the
callback can be executed, and then disturb the ongoing RX DMA transfer.
To avoid such a case, call dmaengine_synchronize in shutdown, after the
DMA RX channel is terminated.

Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
---
 drivers/tty/serial/stm32-usart.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 8fc0526be898..5e9cf0c48813 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -1123,8 +1123,10 @@ static void stm32_usart_shutdown(struct uart_port *port)
 		dev_err(port->dev, "Transmission is not complete\n");
 
 	/* Disable RX DMA. */
-	if (stm32_port->rx_ch)
+	if (stm32_port->rx_ch) {
 		stm32_usart_rx_dma_terminate(stm32_port);
+		dmaengine_synchronize(stm32_port->rx_ch);
+	}
 
 	/* flush RX & TX FIFO */
 	if (ofs->rqr != UNDEF_REG)
-- 
2.25.1

On Thu, Aug 03, 2023 at 03:01:34PM +0200, Valentin Caron wrote:
> From: Amelie Delaunay <amelie.delaunay@foss.st.com>
> 
> In shutdown, RX DMA channel is terminated. If the DMA RX callback is
> scheduled but not yet executed, while a new RX DMA transfer is started, the
> callback can be executed, and then disturb the ongoing RX DMA transfer.
> To avoid such a case, call dmaengine_synchronize in shutdown, after the
> DMA RX channel is terminated.
> 
> Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
> ---

You can't forward on a patch from someone else and not sign-off on it
yourself :(

Please fix up and resend the series.

thanks,

greg k-h