[RFC PATCH 1/2] serial: sh-sci: start hrtimer after setting up DMA

[Wolfram Sang]

In the RX DMA completion handler, the hrtimer was restarted before DMA
was set up. If DMA failed, for some reason, it would clean up and the
hrtimer would run into a NULL-pointer. Restart the timer after DMA was
successfully set up.

Reported-by: Dirk Behme <dirk.behme@xxxxxxxxxxxx>
Closes: https://lore.kernel.org/r/ee6c9e16-9f29-450e-81da-4a8dceaa8fc7@xxxxxxxxxxxx
Fixes: 67f462b069e9 ("serial: sh-sci: Get rid of the workqueue to handle receive DMA requests")
Signed-off-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
---
 drivers/tty/serial/sh-sci.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index e512eaa57ed5..1e3c26c11c49 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -1325,8 +1325,6 @@ static void sci_dma_rx_complete(void *arg)
 	if (active >= 0)
 		count = sci_dma_rx_push(s, s->rx_buf[active], s->buf_len_rx);
 
-	start_hrtimer_us(&s->rx_timer, s->rx_timeout);
-
 	if (count)
 		tty_flip_buffer_push(&port->state->port);
 
@@ -1346,6 +1344,8 @@ static void sci_dma_rx_complete(void *arg)
 
 	dma_async_issue_pending(chan);
 
+	start_hrtimer_us(&s->rx_timer, s->rx_timeout);
+
 	uart_port_unlock_irqrestore(port, flags);
 	dev_dbg(port->dev, "%s: cookie %d #%d, new active cookie %d\n",
 		__func__, s->cookie_rx[active], active, s->active_rx);
-- 
2.43.0