eMMC HS400 mode in IMX8QXP U-Boot

[masood_ahamed]

Hi,

We are trying to enable eMMC HS400 mode in uboot in IMX8QXP based custom board.
In one board we got the following error when enabling HS400 mode, while in another board it is working fine.

CPU: NXP i.MX8QXP RevC A35 at 1200 MHz at 43C

Boot: MMC0
DRAM: 1022 MiB
MMC: FSL_SDHC: 0, FSL_SDHC: 1
Loading Environment from MMC... Select HS400 failed -70
*** Warning - bad CRC, using default environment
In: serial
Out: serial
Err: serial
Select HS400 failed -70
switch to partitions #0, OK
mmc0(part 0) is current device
flash target is MMC:0
Select HS400 failed -70

We have tested with values 0 to 7 for fsl,strobe-dll-delay-target value in usdhc node of u-boot device tree but this error still persists.

We suspect HS400 mode switching is failed due to the failure in the tuning process.

We have also checked the following parameters in usdhc node in u-boot device tree.
1) fsl,start-tuning-tap
2) fsl,tuning-step
We are trying to find out the range of values that can be given to these parameters for testing.
Referring the u-boot source code in driver/mmc/fsl_esdhc_imx.c, following parameters are read from the device tree and updated in TUNING_CTRL register. But when we refer the IMX8QXP reference manual(IMX8DQXPRM.pdf), we could not find any details of TUNING_CTRL register.

Could you please give any information about TUNING_CTRL register?.

Could you please give any hints to resolve this issue.

Thanks.

[igorpadykov · Accepted solution]

Hi masood_ahamed

if issue appears only on one board it may be related to manufacturing process, for

example poor soldering. One can try to resolder chip. Also this may be related to

board noise, one can recheck power supplies using

i.MX 8QuadMax/i.MX 8QuadXPlus Hardware Developer’s Guide

>Could you please give any information about TUNING_CTRL register?.

I am afraid such details are not available, sorry.

Best regards
igor