Re: /dev/mmcblk0 (or /dev/mmcblk0p1) does not exist on Freescale iMX6SL board

Xuebing Wang
2015-05-01T10:39:15Z

On 04/30/2015 09:06 PM, Fabio Estevam wrote:
>> Fabio,
>> >
>> >Thanks. No, I do not have access to a mx6sl-evk. But I can try to get one.
>> >
>> >There is no eMMC (only sd-card) on mx6sl-evk, right?
> That's correct. If you need eMMC with mx6sl, then you can try imx6sl-warp.
>
> I have tested both boards here recently and mmc operation is working fine.

Fabio, thanks.

I got my eMMC working on kernel v4.0.1 by:
1) In device tree, use 8 data lines (rather than 4 lines for sdhc)
2) Force ext_csd.rev to be 4
-------------------------
diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 1d41e85..aa1ca6c 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -355,6 +355,7 @@ static int mmc_decode_ext_csd(struct mmc_card *card,
u8 *ext_csd)
* are authorized, see JEDEC JESD84-B50 section B.8.
*/
card->ext_csd.rev = ext_csd[EXT_CSD_REV];
+ card->ext_csd.rev = 4;

card->ext_csd.raw_sectors[0] = ext_csd[EXT_CSD_SEC_CNT + 0];
card->ext_csd.raw_sectors[1] = ext_csd[EXT_CSD_SEC_CNT + 1];
-------------------------

eMMC on my board is Micron "MTFC4GLDDQ-4M IT", according to its
datasheet, it is "JEDEC/MMC standard version 4.41-compliant
(JEDEC Standard No. 84-A441)", and its "Extended CSD revision"
(EXT_CSD_REV) = 5

This seems either because kernel does not handle (ext_csd == 5)
correctly, or there is an firmware issue in Micron "MTFC4GLDDQ-4M IT"
(in terms of JEDEC standard compliance), what do you think?

--
Xuebing