serial: imx: Introduce timeout when waiting on transmitter empty

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>

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 56b76a221082a15d07257c18888da69dd544ed46..79f1503cd75b41919cd3bb53104c903881f1be24 100644 (file)
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -27,6 +27,7 @@
 #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>
@@ -2002,7 +2003,7 @@ 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)
@@ -2033,8 +2034,8 @@ 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)