Re: [PATCH 1/1] serial: samsung: Clear operation mode on UART shutdown

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Fri, Mar 20, 2015 at 01:19:44PM +0100, Javier Martinez Canillas wrote:
> Hello,
> 
> On 03/13/2015 12:38 PM, Javier Martinez Canillas wrote:
> > Exynos serial ports operate either in a DMA-based or interrupt-based
> > modes. In DMA-based mode, the UART generates a transfer data request
> > and a Transmission (Tx) interrupt in interrupt-based mode.
> > 
> > The Tx IRQ is only unmasked in interrupt-based mode and it was done
> > in s3c24xx_serial_start_tx(). Commit ba019a3e2ad5 ("serial: samsung:
> > remove redundant interrupt enabling") removed the IRQ enable on that
> > function since it is enabled when the mode is set in enable_tx_pio().
> > 
> > The problem is that enable_tx_pio() is only called if the port mode
> > has not been set before but the mode was not cleared on .shutdown().
> > 
> > So if the UART was shutdown and then started up again, the mode set
> > will remain and the Tx IRQ won't be unmasked.
> > 
> > This caused a hang on at least Exynos5250, Exynos5420 and Exynos5800
> > when the system is rebooted or powered off.
> > 
> > Fixes: ba019a3e2ad5 ("serial: samsung: remove redundant interrupt enabling")
> > Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
> > ---
> > 
> > I noticed this issue on an Exynos5250 Snow, Exynos5420 Peach Pit and Exynos
> > 5800 Peach Pi Chromebooks. This patch fixes the issue on all of them.
> > 
> > The offending commit landed in v4.0-rc1 so this fix is -rc material.
> > 
> >  drivers/tty/serial/samsung.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
> > index af821a908720..cf08876922f1 100644
> > --- a/drivers/tty/serial/samsung.c
> > +++ b/drivers/tty/serial/samsung.c
> > @@ -963,6 +963,7 @@ static void s3c24xx_serial_shutdown(struct uart_port *port)
> >  			free_irq(ourport->tx_irq, ourport);
> >  		tx_enabled(port) = 0;
> >  		ourport->tx_claimed = 0;
> > +		ourport->tx_mode = 0;
> >  	}
> >  
> >  	if (ourport->rx_claimed) {
> > 
> 
> Any comments about this patch? 3.14-rc5 will most likely be released this weekend
> so we are running out of time to fix this issue before 3.14 is released.

3.14 was released months ago...