linux-kernel - [RFC PATCH 2/2] serial: sh-sci: always cancel hrtimer when DMA RX is invalidated

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Date: Tue, 16 Apr 2024 14:35:48 +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>,
	Aleksandar Mitev <amitev@...teon.com>,
	linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org
Subject: [RFC PATCH 2/2] serial: sh-sci: always cancel hrtimer when DMA RX is invalidated

Clear the timer whenever 'chan_rx' is cleared to avoid an OOPS.
Currently, the driver only runs the timer when 'chan_rx' is set before.
However, it is good defensive programming to make sure the hrtimer is
always stopped before clearing the 'chan_rx' pointer.

Reported-by: Dirk Behme <dirk.behme@...bosch.com>
Closes: https://lore.kernel.org/r/ee6c9e16-9f29-450e-81da-4a8dceaa8fc7@de.bosch.com
Fixes: 9ab765566086 ("serial: sh-sci: Remove timer on shutdown of port")
Signed-off-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
---

Locking needs to be double-checked here. This patch is mainly calling
for opinions.

 drivers/tty/serial/sh-sci.c | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 1e3c26c11c49..5ad73933c1c5 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -1262,6 +1262,7 @@ static void sci_dma_rx_chan_invalidate(struct sci_port *s)
 {
 	unsigned int i;
 
+	hrtimer_cancel(&s->rx_timer);
 	s->chan_rx = NULL;
 	for (i = 0; i < ARRAY_SIZE(s->cookie_rx); i++)
 		s->cookie_rx[i] = -EINVAL;
@@ -2242,14 +2243,6 @@ static void sci_shutdown(struct uart_port *port)
 		       scr & (SCSCR_CKE1 | SCSCR_CKE0 | s->hscif_tot));
 	uart_port_unlock_irqrestore(port, flags);
 
-#ifdef CONFIG_SERIAL_SH_SCI_DMA
-	if (s->chan_rx_saved) {
-		dev_dbg(port->dev, "%s(%d) deleting rx_timer\n", __func__,
-			port->line);
-		hrtimer_cancel(&s->rx_timer);
-	}
-#endif
-
 	if (s->rx_trigger > 1 && s->rx_fifo_timeout > 0)
 		del_timer_sync(&s->rx_fifo_timer);
 	sci_free_irq(s);
-- 
2.43.0