iMX6 u-Boot MMC driver missing weak/strong pull-up of CMD line

[colinwernham]

I'm trying to add support in u-boot for a Micron eMMC device to the imx6-cubox-i, and it always times-out on the CMD8. Looking at the bootup protocol in the "IMX6DQRM Applications Processor Reference" document, it needs the MMC CMD line "Set Strong pull-up For CMD line" (at the start of the initialisation), then "Set Weak pull-up For CMD line" part of the way through the initialisation (between CMD3 and CMD9).

I am struggling to find a way to modify the u-boot mmc.c driver to set the PAD_SD3_CMD__USDHC3_CMD  PUS and PUE settings from within the driver.

There must be a way to do this. Has the mmc driver been modified to support this for sabreauto which uses eMMC?

Message was edited by: Colin Wernham

[igorpadykov]

Hi Colin

Chapter 8 bootup protocol setups pull-ups in iROM code before running Linux.

After boot Linux uses mmc.c codes, it uses pull-ups setups defined in

dts/dtsi files, no need to additionally control them as it is done in mmc driver.

One can try eMMC operation on sabreauto using Demo images given in BSP,

follow descriptions given in included i.MX_Linux_User's_Guide.pdf

Board Support Packages (29)

L3.14.52_1.1.0_MX6QDLSOLO (REV L3.14.52_1.1.0)

http://www.nxp.com/products/microcontrollers-and-processors/arm-processors/i.mx-applications-process...

Best regards

igor

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[colinwernham]

Hi Igor,

Your info in the Linux kernel is useful, so thanks for that.

I left out of the question that I'm trying to get uBoot to work. Is the iROM you mention equivalent to uboot, and does the SabreAuto use uboot?

I've looked at the git.freescale.com/imx/uboot-imx (which does have config for sabreauto) drivers/mmc/mmc.c code, and cannot see anything that allows additional pullup configuration for the imx6, so I am wondering if it is really necessary, even though the Freescale protocol says it is. Trying to write the pad CMD pullup config inside the driver is not good.

Colin

[igorpadykov · Accepted solution]

Hi Colin

iROM is not equivalent to uboot, uboot link

uboot-imx.git - Freescale i.MX u-boot Tree

additional pullup configuration in mmc.c codes is not necessary, it works

fine with default uboot pull configuration.

Best regards

igor

[colinwernham]

Thanks Igor, that was just what I was looking for!