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Subject[PATCH 4.19 16/52] serial: uartps: Add a timeout to the tx empty wait
Date
From: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>

commit 277375b864e8147975b064b513f491e2a910e66a upstream

In case the cable is not connected then the target gets into
an infinite wait for tx empty.
Add a timeout to the tx empty wait.

Reported-by: Jean-Francois Dagenais <jeff.dagenais@gmail.com>
Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: stable <stable@vger.kernel.org> # 4.19
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/tty/serial/xilinx_uartps.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index 66d49d5118853..7cbee19ea93d5 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -26,6 +26,7 @@
#include <linux/of.h>
#include <linux/module.h>
#include <linux/pm_runtime.h>
+#include <linux/iopoll.h>

#define CDNS_UART_TTY_NAME "ttyPS"
#define CDNS_UART_NAME "xuartps"
@@ -34,6 +35,7 @@
#define CDNS_UART_NR_PORTS 2
#define CDNS_UART_FIFO_SIZE 64 /* FIFO size */
#define CDNS_UART_REGISTER_SPACE 0x1000
+#define TX_TIMEOUT 500000

/* Rx Trigger level */
static int rx_trigger_level = 56;
@@ -681,16 +683,20 @@ static void cdns_uart_set_termios(struct uart_port *port,
unsigned int cval = 0;
unsigned int baud, minbaud, maxbaud;
unsigned long flags;
- unsigned int ctrl_reg, mode_reg;
+ unsigned int ctrl_reg, mode_reg, val;
+ int err;

spin_lock_irqsave(&port->lock, flags);

/* Wait for the transmit FIFO to empty before making changes */
if (!(readl(port->membase + CDNS_UART_CR) &
CDNS_UART_CR_TX_DIS)) {
- while (!(readl(port->membase + CDNS_UART_SR) &
- CDNS_UART_SR_TXEMPTY)) {
- cpu_relax();
+ err = readl_poll_timeout(port->membase + CDNS_UART_SR,
+ val, (val & CDNS_UART_SR_TXEMPTY),
+ 1000, TX_TIMEOUT);
+ if (err) {
+ dev_err(port->dev, "timed out waiting for tx empty");
+ return;
}
}

--
2.20.1


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