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




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