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

[Benoît Thébaudeau]

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).

Best regards,
Benoît