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

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Date: Tue, 16 Apr 2024 14:35:47 +0200
From: Wolfram Sang <wsa+renesas@...g-engineering.com>
To: linux-renesas-soc@...r.kernel.org
Cc: Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Dirk Behme <dirk.behme@...bosch.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org
Subject: [RFC PATCH 1/2] serial: sh-sci: start hrtimer after setting up DMA

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@...bosch.com>
Closes: https://lore.kernel.org/r/ee6c9e16-9f29-450e-81da-4a8dceaa8fc7@de.bosch.com
Fixes: 67f462b069e9 ("serial: sh-sci: Get rid of the workqueue to handle receive DMA requests")
Signed-off-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
---
 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