Enable ddr modes on emmc2 of Raspberry Pi 4 B

Stefan Wahren stefan.wahren at i2se.com
Mon Aug 31 07:32:30 EDT 2020

Hi Tobias,

thanks for providing this patch to lkml [1]. I sent a very similiar one
[2] to linux-mmc after the investigations on the Raspberry Pi github [3].

Can you please explain why this sd-uhs-ddr50 property is necessary?

From my testings with a UHS SD card the UHS DDR50 mode is already
properly configured before your patch.

Is there a specific combination which doesn't work?

Please provide the ios settings of /sys/kernel/debug/mmc1/ios in this
case before applying your patch.

Best regards

[1] -

[2] - https://marc.info/?l=linux-mmc&m=159865133820037

[3] - https://github.com/raspberrypi/linux/issues/3802

More information about the linux-rpi-kernel mailing list