From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tobias Jakobi Subject: Re: [PATCH] serial: samsung: Continue to work if DMA request fails Date: Sat, 25 Feb 2017 17:28:41 +0100 Message-ID: References: <20170225162442.31848-1-krzk@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20170225162442.31848-1-krzk@kernel.org> Sender: linux-samsung-soc-owner@vger.kernel.org To: Krzysztof Kozlowski , Greg Kroah-Hartman , Jiri Slaby , Marek Szyprowski , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org Cc: linux-samsung-soc@vger.kernel.org, stable@vger.kernel.org List-Id: linux-serial@vger.kernel.org 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: > Signed-off-by: Krzysztof Kozlowski > --- > 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 '='? - Tobias > } > } > >