From: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
Date: Mon, 10 Jun 2019 17:23:08 +0000 (+0200)
Subject: tty: serial: msm_serial: avoid system lockup condition
X-Git-Tag: v5.4-rc1~601^2~30
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=ba3684f99f1b25d2a30b6956d02d339d7acb9799;p=platform%2Fkernel%2Flinux-rpi.git

tty: serial: msm_serial: avoid system lockup condition

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>
---

diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
index 23833ad952ba..3657a24913fc 100644
--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -383,10 +383,14 @@ 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);
 }