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    SubjectRe: [PATCH 4.19 16/52] serial: uartps: Add a timeout to the tx empty wait
    On Thu, Feb 13, 2020 at 07:22:46PM +0100, Pavel Machek wrote:
    > 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.

    Good catch, that's a mess. I'll go queue this up now.

    greg k-h

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