[U-Boot] [PATCH 3/4] mmc: exynos dwmmc: check boot mode before init dwmmc

[Tom Rini <trini@ti.com>]

On Wed, Feb 18, 2015 at 11:50:41AM +0100, Przemyslaw Marczak wrote:
> Hello Simon,
> 
> On 02/18/2015 06:02 AM, Simon Glass wrote:
> >Hi Przemyslaw,
> >
> >On 17 February 2015 at 06:09, Przemyslaw Marczak <p.marczak@samsung.com> wrote:
> >>Before this commit, the mmc devices were always registered
> >>in the same order. So dwmmc channel 0 was registered as mmc 0,
> >>channel 1 as mmc 1, etc.
> >>In case of possibility to boot from more then one device,
> >>the CONFIG_SYS_MMC_ENV_DEV should always point to right mmc device.
> >>
> >>This can be achieved by init boot device as first, so it will be
> >>always registered as mmc 0. Thanks to this, the 'saveenv' command
> >>will work fine for all mmc boot devices.
> >>
> >>Exynos based boards usually uses mmc host channels configuration:
> >>- 0, or 0+1 for 8 bit  - as a default boot device (usually eMMC)
> >>- 2 for 4bit - as an optional boot device (usually SD card slot)
> >>
> >>And usually the boot order is defined by OM pin configuration,
> >>which can be changed in a few ways, eg.
> >>- Odroid U3     - eMMC card insertion -> first boot from eMMC
> >>- Odroid X2/XU3 - boot priority jumper
> >>
> >>By this commit, Exynos dwmmc driver will check the OM pin configuration,
> >>and then try to init the boot device and register it as mmc 0.
> >
> >I think a better way to do this would be to make
> >CONFIG_SYS_MMC_ENV_DEV support an option where the device can be
> >selected at run-time.
> >
> >However that would probably be better done when the drive rmodel
> >conversion is complete.
> >
> >So this seems a reasonable patch given where we are.
> >
> >Reviewed-by: Simon Glass <sjg@chromium.org>
> >
> 
> This was just a quick solution to solve the issue on XU3, when the
> same binary can boot from sd or eMMC slots.

XU3 isn't unique in this regard.  "am335x_evm" binaries runs on 4 very
different boards and we still just have to say that sometimes we default
to ENV in a place that isn't workable.
 
-- 
Tom
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