[U-Boot] [PATCH] imx: mx6sxsabresd: support emmc

[Peng Fan]

Hi Stefano,

On Sun, Jan 24, 2016 at 12:07:14PM +0100, Stefano Babic wrote:
>Hi Peng,
>
>On 23/12/2015 04:10, Peng Fan wrote:
>> Hi Otavio,
>> On Tue, Dec 22, 2015 at 09:51:37AM -0200, Otavio Salvador wrote:
>>> On Tue, Dec 22, 2015 at 7:03 AM, Peng Fan <van.freenix at gmail.com> wrote:
>>>> From: Peng Fan <peng.fan at nxp.com>
>>>>
>>>> For i.MX6SX SABRESD, USDHC4 can be used for SD and EMMC, default
>>>> it is used for SD.
>>>>
>>>> This patch introduces EMMC pinmux settings and a new macro
>>>> CONFIG_MX6SXSABRESD_EMMC_REWORK. If the board has been reworked
>>>> to support emmc, need to enable this macro.
>>>>
>>>> Signed-off-by: Peng Fan <peng.fan at nxp.com>
>>>> Cc: Stefano Babic <sbabic at denx.de>
>>>
>>> Is it worth supporting this 'reworked' board? if someone reworks a
>>> board it is expected to have to rework the BSP of it, as well.
>> 
>> usdhc4 can be used for SD and emmc. This is the feature of the board,
>> so I think we need to support it. But there is no way to dynamically check
>> whether using sd or emmc now, adding the macro for using emmc.
>
>I agree with Otavio that this is a very nasty hack, and the hardware
>developer should provide a way getting the board revision. Anyway, I
>would not certainly block it, as it concerns just this board, but I ask
>if it is not better to let decide to an environment variable if eMMC
>must be activated. Advantage is to have a single U-Boot binary for both
>boards, disadvantage is that it coul be set for the wrong board
>revision, too. But if USDHC4 was not used anymore, this drives just to a
>not found eMMC. Both ways are hacks, I fully agree, but
>CONFIG_MX6SXSABRESD_EMMC_REWORK remains undocumented at all, too.
>
>What do you think ?

There is no fuse bit or else to let uboot do runtime checking. I also
disklike this, but I do not have a better idea. Without runtime checking,
it's hard to use one image support SD/EMMC both. I would like to
add doc for the macro CONFIG_MX6SXSABRESD_EMMC_REWORK in the next version, do you agree with
this?

Thanks,
Peng.
>
>Best regards,
>Stefano Babic
>
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