I have a custom designed board using the compute module 3+, booting from the EMMC with an SD card interface connected to GPIO 34-39. From what I've read elsewhere the only thing I need to do is to setup the sdio overlay in /boot/config.txt:
The output of
vcdbg log msg indicates the overlay was loaded correctly however the output of
mmc1: card never left busy state mmc1: error -110 whilst initialising SD card
Is there something more or different that I should be doing to get the SD card interface to work? Its possible that the issue is with the connections on the custom board however I want to make sure I am doing everything correctly from the software side before I go back to the engineers at the board house.
UPDATE It turns out the SD card interface wasn't getting power due to a hardware issue however I am still unable to get the SD card to work, the error message has changed to:
mmc1: host does not support reading read-only switch, assuming write-enable mmc1: error -110 whilst initialising SD card