MMC/SD Speed Settings/Setup in Device Tree

General Discussion
1

I’d like to run my SD card speed slower than the default 50MHz; I’ve looked at
https://u-boot.readthedocs.io/en/v2022.04-rc2/usage/mmc.html
and it seems there is a way to do this with the device tree.

Does anyone have experience with this? I’ve done device tree work before, but not in this area.

thanks!

2

There is a max-frequency specification in the mmc device-tree:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/mmc/mmc-controller.yaml?h=v5.18#n90

Regards,

3

Thanks! Looks like the default range is 400kHz–200MHz

So if I wanted to do an overlay…is there a baseline overlay that affects the mmc that I can start with? I have used them for other peripherals like i2c, pwm, and encoders.