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

[Przemyslaw Marczak <p.marczak@samsung.com>]

Hello Tom,

On 02/19/2015 03:03 PM, Tom Rini wrote:
> 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.
>
>

Yes, I saw this issue on bb black. But it seems to be not a big problem 
to fix it.
When I finish the pmic and finally start work on adding it to the bb 
black, then maybe I will try to fix it somehow.

Regards,
-- 
Przemyslaw Marczak
Samsung R&D Institute Poland
Samsung Electronics
p.marczak at samsung.com