serial: sh-sci: Terminate TX DMA during buffer flushing

BugLink: https://bugs.launchpad.net/bugs/1839036
[ Upstream commit 775b7ffd7d6d5db320d99b0a485c51e04dfcf9f1 ]

While the .flush_buffer() callback clears sci_port.tx_dma_len since
commit 1cf4a7efdc71cab8 ("serial: sh-sci: Fix race condition causing
garbage during shutdown"), it does not terminate a transmit DMA
operation that may be in progress.

Fix this by terminating any pending DMA operations, and resetting the
corresponding cookie.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Tested-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Link: https://lore.kernel.org/r/20190624123540.20629-3-geert+renesas@glider.be
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 67741c84584ecf4cf3e69b886dbc1e63797acb59..9eaf20b29384bd47fa1c189140612e5cfe733312 100644 (file)
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -1589,11 +1589,18 @@ static void sci_free_dma(struct uart_port *port)
 
 static void sci_flush_buffer(struct uart_port *port)
 {
+       struct sci_port *s = to_sci_port(port);
+
        /*
         * In uart_flush_buffer(), the xmit circular buffer has just been
-        * cleared, so we have to reset tx_dma_len accordingly.
+        * cleared, so we have to reset tx_dma_len accordingly, and stop any
+        * pending transfers
         */
-       to_sci_port(port)->tx_dma_len = 0;
+       s->tx_dma_len = 0;
+       if (s->chan_tx) {
+               dmaengine_terminate_async(s->chan_tx);
+               s->cookie_tx = -EINVAL;
+       }
 }
 #else /* !CONFIG_SERIAL_SH_SCI_DMA */
 static inline void sci_request_dma(struct uart_port *port)