Let me revive this thread, finally I found time to get into the issue again.
I use the latest C4 server image (Ubuntu 24.04).
Changes made so far: I added a line
fdtfile=amlogic/meson-sm1-odroid-c4-spidev.dtb
into the armbianEnv.txt, which seems at least to load the spidev kernel module.
A /dev/spidev0.0 is created, and I can use the standard test program found on https://github.com/KnCMiner/spi-test/blob/master/spi-test.c
It seems to work, there are no errors invoking the program, but the I/Os of SPI stay inactive, no matter what I do.
gpioinfo shows the lines on PIN_19, PIN_21, PIN_23 and PIN_24 as "unused":
Seem that basically the SPI controller is working, but the I/O mux is not setup correctly.
Anyone who can contribute here? I can test with logic analyzer, in case some input is given to me