How to configure usdhc (SD card pinout) to UHS-1 (SDR 104)?


I am trying to set my microSD card pinout to UHS-1 (SDR 104)

SoM : Apalis iMX8 QuadPlus 2GB V1.1C
microSD : (MFG PN: AP-MSD04GCA-1HTM)
microSD file system : ext4
Yocto Image : Toradex Embedded Linux Quarterly Releases
Reference Images for Yocto Project Software Downloads | Toradex Developer Center

I tested in my own customized carrier board,
using SD_2 port (with external pull up 1.8V)
please refer to imx8-apalis-v1.1.dtsi « freescale « dts « boot « arm64 « arch - linux-toradex.git - Linux kernel for Apalis, Colibri and Verdin modules


Below is the result:
dmesg | grep mmc

cat /sys/kernel/debug/mmc1/ios

Tested SD_1 port in Apalis Evaluation Board, also show as high speed mode. (same result)

Please teach me how to do, thanks

@alex.tx , @gustavo.tx ,

after remove the remove the property ‘no-1-8-v’ , seems like we can set to Ultra High Speed successfully according to dmesg

cat /sys/kernel/debug/mmc1/ios

The read speed is ~ 76.16MB / sec (meet expectation)

The write speed ~ 15MB / sec (50MB is expected !!)

Please share us the solution if you know, thank you

@alex.tx , @gustavo.tx ,

Latest update, the write speed is slow I think because I am using 4GB sd card, and the file size is too large (500MB),

Now I change my file to 200MB, and the write speed is around ~40 or 50 MB / S

Hi, aside from Software configuration, for Hardware side do I need to have 1.8V pull up for the signals when running for UHS-1?

Hi, is there any update for this?

Hi @tanchunhau

As per the Apalis imx8QM data sheet chapter 5.14 ,"If the interfaces are used in the 1.8V mode, it is recommended to remove the pull up resistors on the carrier board."

Hi @ashok.tx , thanks for the clarification! The reason we are asking for this is because with some reworks on the board, it was found that the performance of having a 1.8V pull up is more stable and consistent than the one without pull up. So, I would like to ensure that the pull up is really unnecessary and the inconsistency is maybe caused by the hand reworks which we are now building another board to confirm our design for this SD Interface. Thanks ya! :grinning: