serial: samsung: Continue to work if DMA request fails

BugLink: http://bugs.launchpad.net/bugs/1674288
commit f98c7bce570bdbe344b74ff5daa7dfeef3f22929 upstream.

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=0x00000000

DMA is not necessary for serial to work, so continue with UART startup
after emitting a warning.

Fixes: 62c37eedb74c ("serial: samsung: add dma reqest/release functions")
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
index f44615fa474de233748b4f72133b8bf3fc272bf5..3e2ef4fd738251645a6e5d75efb0cd20df41b329 100644 (file)
--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -1036,8 +1036,10 @@ static int s3c64xx_serial_startup(struct uart_port *port)
        if (ourport->dma) {
                ret = s3c24xx_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 = NULL;
                }
        }