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SubjectRe: [PATCH 4.19 16/52] serial: uartps: Add a timeout to the tx empty wait
Hi!

> 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.

Was this tested? Because it does not work...

> 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>

> @@ -681,16 +683,20 @@ static void cdns_uart_set_termios(struct uart_port *port,
...
> + 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;
> }
> }
>

It will return with lock held and interrupts disabled. Mainline takes
spinlock later, so it does not have a problem.

Merging 107475685abfdee504bb0ef4824f15797f6d2d4d before this one
should fix the problem.

Best regards,
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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