Re: [PATCH] serial: samsung: Continue to work if DMA request fails

From: Krzysztof Kozlowski
Date: Sat Feb 25 2017 - 11:35:28 EST


On Sat, Feb 25, 2017 at 05:28:41PM +0100, Tobias Jakobi wrote:
> Hello Krzysztof,
>
> Krzysztof Kozlowski wrote:
> > If DMA is not available (even when configured in DeviceTree), the driver
> > will fail the startup procedure thus making serial console not
> > available.
> >
> > For example this causes boot failure on QEMU ARMv7 (Exynos4210, SMDKC210):
> > [ 1.302575] OF: amba_device_add() failed (-19) for /amba/pdma@12680000
> > ...
> > [ 11.435732] samsung-uart 13800000.serial: DMA request failed
> > [ 72.963893] samsung-uart 13800000.serial: DMA request failed
> > [ 73.143361] Kernel panic - not syncing: Attempted to kill init! exitcode=00000000
> >
> > DMA is not necessary for serial to work, so continue with UART startup
> > after emitting a warning.
> >
> > Fixes: Fixes: 62c37eedb74c ("serial: samsung: add dma reqest/release functions")
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > Signed-off-by: Krzysztof Kozlowski <krzk@xxxxxxxxxx>
> > ---
> > drivers/tty/serial/samsung.c | 6 ++++--
> > 1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
> > index b4f86c219db1..7a17aedbf902 100644
> > --- a/drivers/tty/serial/samsung.c
> > +++ b/drivers/tty/serial/samsung.c
> > @@ -1031,8 +1031,10 @@ static int s3c64xx_serial_startup(struct uart_port *port)
> > if (ourport->dma) {
> > ret =3c24xx_serial_request_dma(ourport);
> > if (ret < 0) {
> > - dev_warn(port->dev, "DMA request failed\n");
> > - return ret;
> > + dev_warn(port->dev,
> > + "DMA request failed, DMA will not be used\n");
> > + devm_kfree(port->dev, ourport->dma);
> > + ourport->dma =ULL;
> This line looks odd. Did you want to assign NULL here?
> Also, whitespace on both sides of '='?

Ugh, I must ate it by mistake somehow because my git contains proper
"NULL" here.

Thanks for pointing this, I'll resend v3.


Best regards,
Krzysztof