[PATCH AUTOSEL 6.1 08/12] serial: imx: Introduce timeout when waiting on transmitter empty

Sasha Levin
2024-06-05T11:53:51Z

From: Esben Haabendal <esben@geanix.com>

[ Upstream commit e533e4c62e9993e62e947ae9bbec34e4c7ae81c2 ]

By waiting at most 1 second for USR2_TXDC to be set, we avoid a potential
deadlock.

In case of the timeout, there is not much we can do, so we simply ignore
the transmitter state and optimistically try to continue.

Signed-off-by: Esben Haabendal <esben@geanix.com>
Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>
Link: https://lore.kernel.org/r/919647898c337a46604edcabaf13d42d80c0915d.1712837613.git.esben@geanix.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/tty/serial/imx.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 573bf7e9b7978..b20abaa9ef150 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -27,6 +27,7 @@
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/io.h>
+#include <linux/iopoll.h>
#include <linux/dma-mapping.h>

#include <asm/irq.h>
@@ -2028,7 +2029,7 @@ imx_uart_console_write(struct console *co, const char *s, unsigned int count)
struct imx_port *sport = imx_uart_ports[co->index];
struct imx_port_ucrs old_ucr;
unsigned long flags;
- unsigned int ucr1;
+ unsigned int ucr1, usr2;
int locked = 1;

if (sport->port.sysrq)
@@ -2059,8 +2060,8 @@ imx_uart_console_write(struct console *co, const char *s, unsigned int count)
* Finally, wait for transmitter to become empty
* and restore UCR1/2/3
*/
- while (!(imx_uart_readl(sport, USR2) & USR2_TXDC));
-
+ read_poll_timeout_atomic(imx_uart_readl, usr2, usr2 & USR2_TXDC,
+ 0, USEC_PER_SEC, false, sport, USR2);
imx_uart_ucrs_restore(sport, &old_ucr);

if (locked)
--
2.43.0