patch "serial: samsung: Continue to work if DMA request fails" added to tty-linus

This is a note to let you know that I've just added the patch titled

serial: samsung: Continue to work if DMA request fails

to my tty git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From: Krzysztof Kozlowski <[email protected]>
Date: Sat, 25 Feb 2017 18:36:44 +0200
Subject: serial: samsung: Continue to work if DMA request fails
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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.

---
 drivers/tty/serial/samsung.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

index b4f86c219db1..7a17aedbf902 100644
@@ -1031,8 +1031,10 @@ 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;
 		}
 	}
 

2.12.0