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How to set HS400 mode of eMMC from uboot in i.MX 8M Quad EVK?

Question asked by Andy Lee on Apr 22, 2019
Latest reply on Apr 23, 2019 by igorpadykov

I'm using i.MX 8M Quad EVK board and then found eMMC is not set to HS400 mode.


u-boot=> mmc info
Device: FSL_SDHC
Manufacturer ID: 13
OEM: 14e
Name: R1J56
Bus Speed: 52000000
Mode : MMC DDR52 (52MHz)
Rd Block Len: 512
MMC version 5.0
High Capacity: Yes
Capacity: 13.8 GiB
Bus Width: 8-bit DDR
Erase Group Size: 512 KiB
HC WP Group Size: 8 MiB
User Capacity: 13.8 GiB WRREL
Boot Capacity: 4 MiB ENH
RPMB Capacity: 128 KiB ENH


But after booting is complete, kernel shows that eMMC is set to HS400.


evk_8mq:/ # cat /sys/kernel/debug/mmc0/ios
clock: 200000000 Hz
actual clock: 200000000 Hz
vdd: 21 (3.3 ~ 3.4 V)
bus mode: 2 (push-pull)
chip select: 0 (don't care)
power mode: 2 (on)
bus width: 3 (8 bits)
timing spec: 10 (mmc HS400)
signal voltage: 1 (1.80 V)
driver type: 0 (driver type B)