[PATCH V1] tty: serial: fsl_lpuart: add timeout for wait_event_interruptible in .shutdown()

[Sherry Sun]

Use wait_event_interruptible in lpuart_dma_shutdown isn't a reasonable
behavior, since it may cause the system hang here if the condition
!sport->dma_tx_in_progress never to be true in some corner case, such as
when enable the flow control, the dma tx request may never be completed
due to the peer's CTS setting when run .shutdown().

So here change to use wait_event_interruptible_timeout instead of
wait_event_interruptible, the tx dma will be forcibly terminated if the
tx dma request cannot be completed within 30ms.
The 30ms here is same as the time waiting for the transmitter to empty
in uart_suspend_port().

Signed-off-by: Sherry Sun <sherry.sun@xxxxxxx>
---
 drivers/tty/serial/fsl_lpuart.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index ac5112def40d..78b2730e43d3 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1793,8 +1793,8 @@ static void lpuart_dma_shutdown(struct lpuart_port *sport)
 	}
 
 	if (sport->lpuart_dma_tx_use) {
-		if (wait_event_interruptible(sport->dma_wait,
-			!sport->dma_tx_in_progress) != false) {
+		if (wait_event_interruptible_timeout(sport->dma_wait,
+			!sport->dma_tx_in_progress, msecs_to_jiffies(30)) <= 0) {
 			sport->dma_tx_in_progress = false;
 			dmaengine_terminate_all(sport->dma_tx_chan);
 		}
-- 
2.17.1