[U-Boot] [BUG] snow: mmc: SD card access broken: unable to select a mode

[Jean-Jacques Hiblot]

On 09/04/2018 14:02, Guillaume Gardet wrote:
> Hi Jaehoon,
>
> There are problems with SD card access on Samsung Chromebook (snow) 
> with latest master (and also 2018.05-rc1 and 2018.03).
>
> eMMC is ok, but SD card access leads to 'unable to select a mode' 
> problem. If I disable HS mode, I can access the SD card without problem:
> ******************************************************************************** 
>
> diff --git a/drivers/mmc/dw_mmc.c b/drivers/mmc/dw_mmc.c
> index 23f642980bf..28f4fa0f213 100644
> --- a/drivers/mmc/dw_mmc.c
> +++ b/drivers/mmc/dw_mmc.c
> @@ -508,7 +508,8 @@ void dwmci_setup_cfg(struct mmc_config *cfg, 
> struct dwmci_host *host,
>          cfg->host_caps |= MMC_MODE_4BIT;
>          cfg->host_caps &= ~MMC_MODE_8BIT;
>      }
> -    cfg->host_caps |= MMC_MODE_HS | MMC_MODE_HS_52MHz;
> +    /* Temp workaround for Chromebook snow to avoid the 'unable to 
> select a mode' error */
> +//     cfg->host_caps |= MMC_MODE_HS | MMC_MODE_HS_52MHz;
>
>      cfg->b_max = CONFIG_SYS_MMC_MAX_BLK_COUNT;
>  }
> ******************************************************************************** 
>
>
> Once we try to select HS mode, all access to SD card result in 
> failure, even when trying to setup a lower frequency mode, including 
> SD legacy at 25 MHz.
>
> Any idea what is going? Maybe you have fixes pending?

Can try with MMC_MODE_HS | MMC_MODE_HS_52MHz but with a lower 
max-frequency (<25MHz) ? It would be interesting to know if it could 
come from a frequency limitation.
Is there some pad configuration to do when using higher frequency?

JJ

>
>
> Guillaume
>
>
>