serial: stm32: synchronize RX DMA channel in shutdown

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>
Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
Link: https://lore.kernel.org/r/20230808161906.178996-7-valentin.caron@foss.st.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 8fc0526..5e9cf0c 100644 (file)
--- 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)