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

[Guillaume Gardet]

Le 09/04/2018 à 15:58, Jean-Jacques Hiblot a écrit :
>
>
> 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.

I already tried to change SD_HS freq (in mmc_mode2freq) from 50000000 to 25000000 with no difference.

> Is there some pad configuration to do when using higher frequency?

I do not think so.

Guillaume



>
> JJ
>
>>
>>
>> Guillaume
>>
>>
>>
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