tty: serial: msm_serial: avoid system lockup condition

[ Upstream commit ba3684f99f1b25d2a30b6956d02d339d7acb9799 ]

The function msm_wait_for_xmitr can be taken with interrupts
disabled. In order to avoid a potential system lockup - demonstrated
under stress testing conditions on SoC QCS404/5 - make sure we wait
for a bounded amount of time.

Tested on SoC QCS404.

Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
index 716aa76abdf9888bb23e023f9c9599e2775d0f5b..0e0ccc132ab0f35318a03df65a4c7d4f0d0c858a 100644 (file)
--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -391,10 +391,14 @@ no_rx:
 
 static inline void msm_wait_for_xmitr(struct uart_port *port)
 {
+       unsigned int timeout = 500000;
+
        while (!(msm_read(port, UART_SR) & UART_SR_TX_EMPTY)) {
                if (msm_read(port, UART_ISR) & UART_ISR_TX_READY)
                        break;
                udelay(1);
+               if (!timeout--)
+                       break;
        }
        msm_write(port, UART_CR_CMD_RESET_TX_READY, UART_CR);
 }