[RFC PATCH v2 1/2] serial: imx: Introduce timeout when waiting on transmitter empty

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By waiting at most 1 second for USR2_TXDC to be set, we avoid a potentital
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@xxxxxxxxxx>
---
 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 54b760d845c0..f7e4f38f08f3 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -26,6 +26,7 @@
 #include <linux/slab.h>
 #include <linux/of.h>
 #include <linux/io.h>
+#include <linux/iopoll.h>
 #include <linux/dma-mapping.h>
 
 #include <asm/irq.h>
@@ -1995,7 +1996,7 @@ 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)
@@ -2026,8 +2027,8 @@ 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, 1000000, false, sport, USR2);
 	imx_uart_ucrs_restore(sport, &old_ucr);
 
 	if (locked)
-- 
2.44.0





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