EMMC 5.0 and EMMC 5.1 work on i.MX6

Document created by Rita Wang Employee on Jun 29, 2016Last modified by Rita Wang Employee on Aug 21, 2017
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In our reference design board the eMMC IC is Sandisk SDIN5C2-8 (4.41), and in i.MX6 Reference manual and datasheet we can known that it compatible with the MMC System Specification version 4.2/4.3/4.4, and details in datasheet declare that the uSDHC module is "fully compliant with the MMC command/response sets and Physical Layer as defined in the Multimedia Card System Specification, v4.2/4.3/4.4/4.41, including high-capacity (> 2 GB) HC MMC cards." EMMC4.4/4.41 of cause can work in our released BSP.

But eMMC 4.4 has been discontinued and there is a possibility eMMC 4.41 will be discontinued.  And many of our customers will choose the eMMC 4.5 or high verison EMMC 5.0 and EMMC 5.1. And how to make the eMMC 4.5 , EMMC 5.0 and EMMC 5.1 work on i.MX6 ?

The EMMC 4.5 or EMMC 5.0 /5.1 is backward-compatible with eMMC4.4, we can use it in eMMC4.4 mode to enable eMMC4.4 functionality and performance on the i.MX6 platform. Booting from a eMMC 4.5 device or high version is not supported,  boot ROM will fall back to the eMMC4.4 standard when a eMMC4.5 or high version capable device is detected. In BSP it is possible to bypass eMMC version checking, so that eMMC v4.5 or high version can work as eMMC v4.4 cards, no specific v4.5 feature supported. Only basic read/write operations are supported.

In the source code we can change check value of card->ext_csd.rev.

Take the eMMC 4.5 work as example, the current i.MX6 Linux BSP (L3.0.35_4.1.0) has added code to interface with an eMMC4.5 card to operate as an eMMC4.4 card. Change the value of card->ext_csd.rev 5 to 6, now eMMC 5.0 can work as an eMMC 4.4. The code drivers/mmc/core/mmc.c:



And for the EMMC 5.0 and EMMC5.1, modify the kernel to support eMMC 5.0 and 5.1 extended CSD revisions, as shown below:

/drivers/mmc/core/mmc.c :

if (card->ext_csd.rev > 6) {              // The '6' has to be replaced with '7' For EMMC5.0

                                                        //  The '6' has to be replaced with '8'  For EMMC5.1

pr_err("%s: unrecognised EXT_CSD revision %d\n",

mmc_hostname(card->host), card->ext_csd.rev);

err = -EINVAL;

goto out;


After modifying the code we need to rebuild the the firmware uImage used for MfgTool . Update the uImage in Mfgtool , and it can flash successful.

Then the eMMC version 5.0 and 5.1 can be used with IMX6 based boards.

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