diff mbox series

[3/4] serial: sh-sci: let timeout timer only run when DMA is scheduled

Message ID 20240506114016.30498-9-wsa+renesas@sang-engineering.com (mailing list archive)
State Accepted
Delegated to: Geert Uytterhoeven
Headers show
Series serial: sh-sci: response to Dirk's bugreport | expand

Commit Message

Wolfram Sang May 6, 2024, 11:40 a.m. UTC
The hrtimer for RXDMA timeout was unconditionally restarted in the RXDMA
complete handler ignoring the fact that setting up DMA may fail and PIO
is used instead. Explicitly stop the timer when DMA is completed and
only restart it when setting up DMA was successful. This makes the
intention of the timer much clearer, the driver easier to understand and
simplifies assumptions about the timer. The latter avoids race
conditions if these assumptions were not met or confused.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
 drivers/tty/serial/sh-sci.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 09eb0c824b10..7cc354ee6305 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -1325,14 +1325,14 @@  static void sci_dma_rx_complete(void *arg)
 	dev_dbg(port->dev, "%s(%d) active cookie %d\n", __func__, port->line,
 		s->active_rx);
 
+	hrtimer_cancel(&s->rx_timer);
+
 	uart_port_lock_irqsave(port, &flags);
 
 	active = sci_dma_rx_find_active(s);
 	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);
 
@@ -1355,6 +1355,9 @@  static void sci_dma_rx_complete(void *arg)
 	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);
+
+	start_hrtimer_us(&s->rx_timer, s->rx_timeout);
+
 	return;
 
 fail: