[U-Boot] [RFC] mmc: fsl_esdhc: Do not set high speed mode on MX25 and MX51

[Benoît Thébaudeau]

On 18/10/2017 at 18:13, Benoît Thébaudeau wrote:
> Hi Fabio,
> 
> On 18/10/2017 at 17:57, Fabio Estevam wrote:
>> Currently when a high speed SD card is connected on MX25 or MX51 boards
>> the following error happens:
>>
>> U-Boot 2017.11-rc2 (Oct 18 2017 - 13:49:26 -0200)
>>
>> CPU:   Freescale i.MX51 rev3.0 at 800 MHz
>> Reset cause: POR
>> Board: MX51EVK
>> DRAM:  512 MiB
>> MMC:   FSL_SDHC: 0, FSL_SDHC: 1
>> *** Warning - read failed, using default environment
>>
>> In:    serial
>> Out:   serial
>> Err:   serial
>> Net:   FEC
>> Hit any key to stop autoboot:  0
>> => saveenv
>> Saving Environment to MMC...
>> Writing to MMC(0)... failed
>>
>> Workaround this issue by not setting the mmc high speed mode flags even
>> if the HOSTCAPBLT register reports that the SD card can operate at
>> high speed.
>>
>> Tested on imx51evk and imx25pdk boards.
>>
>> Signed-off-by: Fabio Estevam <fabio.estevam at nxp.com>
>> ---
>> Kernel is capable of running the SD card at 50MHz clock, but U-Boot fails.
>>
>> I haven't had a chance to debug this further, but sending it as RFC in case
>> someone has some suggestions.
> 
> [...]
> 
> You could stress-test the SD read/write accesses from U-Boot. Does it occur with
> all HS cards?
> 
> You can try to set the drive strength of all the eSDHC pads to high or max (for
> each pad or for the group of pads depending on the register layout for the pads
> used on the board). This worked on my board (custom i.MX25-based, not imx25pdk).

And set SRE to fast too.

Benoît