[U-Boot] [PATCH 1/3] samsung: board: support eMMC reset using DT

[Sjoerd Simons]

On Thu, 2015-01-08 at 14:44 +0900, Joonyoung Shim wrote:
> Some exynos boards require special handling of SD4_nRESET_OUT line for
> eMMC memory to perform complete reboot e.g. Odroid X2/U3/XU3 boards.
> 
> This will support eMMC reset using DT from reset_misc of samsung common
> board file and each board files can support eMMC reset on non DT case.
> 
> Signed-off-by: Joonyoung Shim <jy0922.shim at samsung.com>

> diff --git a/doc/device-tree-bindings/exynos/emmc-reset.txt b/doc/device-tree-bindings/exynos/emmc-reset.txt
> new file mode 100644
> index 0000000..e48e508
> --- /dev/null
> +++ b/doc/device-tree-bindings/exynos/emmc-reset.txt
> @@ -0,0 +1,15 @@
> +* Samsung eMMC reset
> +
> +Some exynos boards require special handling of SD4_nRESET_OUT line for eMMC
> +memory to perform complete reboot.

Nitpick, on XU3 the line you apparently need to twiddle is
SD0_nRESET_OUT.

Is this type of usage of this pin specific to the Odroid Exynos boards
or potentially on more boards? (Sorry for the simple questions, but my
exynos documentation just says the line exists not what its intended
usage is). 

Fwiw, I did a quick check in the linux code and it doesn't seem to be
using those pins for currently for any boards. However my X2 does
successfully reset/reboot in u-boot and linux, so it seems optional
there. The XU3 does fail to reset itself, so it seems required for that
board.

> +Required properties:
> +- compatible: should be "samsung,emmc-reset"
> +- reset-gpio: gpio chip for eMMC reset.
> +
> +Example:
> +
> +emmc-reset {
> +        compatible = "samsung,emmc-reset";
> +        reset-gpio = <&gpk1 2 0>;
> +};


-- 
Sjoerd Simons <sjoerd.simons at collabora.co.uk>
Collabora Ltd.
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