IMX6 u-boot v2017 boot from MMC mmc_init: -110 error

[david_schmidt]

Hello community,

I have a problem regarding booting from MMC on my custom IMX6Dual board, using U-Boot version branch imx_v2017.03_4.9.51_imx8_beta2.

On most of my boards the boot process works. I can select my mmc dev 1 and get the following trace log:

boot_mmc_good_log - Pastebin.com 

switch to partitions #0, OK
mmc1(part 0) is current device

But on some of the boards, selecting mmc dev 1 fails with the following trace logs:

boot_mmc_bad_log - Pastebin.com 

mmc_init: -110, time 128

This is the code that fails in drivers/mmc/mmc.c in function static int mmc_startup(struct mmc *mmc):

/* Put the Card in Identify Mode */
cmd.cmdidx = mmc_host_is_spi(mmc) ? MMC_CMD_SEND_CID :
MMC_CMD_ALL_SEND_CID; /* cmd not supported in spi */
cmd.resp_type = MMC_RSP_R2;
cmd.cmdarg = 0;

do {
     err = mmc_send_cmd(mmc, &cmd, NULL);
} while (err && retries-- > 0);

if (err)
    return err;

This problem did not occur on my boards with the U-Boot v2014 version.

How can I resolve this issue?

[david_schmidt · Accepted solution]

So I found the issue that caused the init_error.

In drivers/mmc/mmc.c in function static int mmc_send_op_cond(struct mmc *mmc):

changing the OCR busy flag evaluation from 

if (mmc->ocr & OCR_BUSY)

            break;

to

if (!(mmc->ocr & OCR_BUSY))

            break;

and the MMC is initialized properly. I honestly have no idea why this flag is assumed to be inverted.

Thanks anyway for the help!

[david_schmidt]

Hi Igor,

thank you for the response.

Unfortunately I get the same error with the imx_v2017.03_4.9.88 branch.

How can I tweak the MMC driver?

[igorpadykov]

Hi David

one can check

https://community.nxp.com/thread/332110 

~igor

[david_schmidt]

Hi Igor,

thank you for the tip.

Sadly, increasing the driver strength of the MMC pins by changing:

#define USDHC_PAD_CTRL (PAD_CTL_PUS_47K_UP |            \

    PAD_CTL_SPEED_LOW | PAD_CTL_DSE_80ohm |         \

    PAD_CTL_SRE_FAST | PAD_CTL_HYS)

to 

#define USDHC_PAD_CTRL (PAD_CTL_PKE | PAD_CTL_PUE | \

PAD_CTL_PUS_22K_UP | PAD_CTL_SPEED_LOW | \

PAD_CTL_DSE_120ohm | PAD_CTL_SRE_FAST | PAD_CTL_HYS)

did not help either. I still get the mmc_init error.

The strange thing is, with the version 2014 of u-boot, I don't get this error accessing MMC.

On some boards, the first selection of my mmc dev 1 works, but the second selection of mmc dev 1 fails with the init error.

Is there anything else I could try?

[david_schmidt]

Hi Igor,

can you help me what other parts you mean? Most other solutions seem to be related to the linux kernel, but because the MMC device is not found, I can't boot into kernel.

I know the DDR settings and the hardware are not the issue, because everything worked with u-boot v2014 and kernel 3.14.

Porting to new u-boot now and the problem appeared. 

The MMC is soldered directy to the board.

[igorpadykov]

Hi David

different emmc parts may have different drive strengths, so you can try

with any other available emmc. i.MX drive strength may be adjusted in linux dts file,

for example:

        pinctrl_usdhc2: usdhc2grp {
            fsl,pins = <
                MX6QDL_PAD_SD2_CMD__SD2_CMD        0x17059

during boot, please check sect.Table 8-14. USDHC boot eFUSE descriptions

i.MX6DQ Reference Manual
https://www.nxp.com/docs/en/reference-manual/IMX6DQRM.pdf

BOOT_CFG2[0]  Override pad settings 1 - Use PAD_SETTINGS values

Best regards
igor

[igorpadykov]

Hi David

one can try with other emmc parts as in the case

eMMC 8GB to 4GB - crash on linux (yocto) boot 

Best regards
igor

[igorpadykov]

Hi David

in general one try to tweak driver strength of i.mx, emmc signals, however

imx_v2017.03_4.9.51_imx8_beta2 was not tested with i.MX6DQ, recommended to use imx_v2017.03_4.9.88

uboot-imx - i.MX U-Boot 

link below shows which software versions should be used for each i.mx family

i.MX Software|NXP 

Best regards
igor
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