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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