I am running Debian Bullseye on a Variscite iMX8 SoM. I have SPI mostly working both in code (C++) and from the command line. I have verified the signals with a logic analyzer. Unfortunately, the pin that is supposed to be the CS pin is always stuck low and never changes state no matter how I configure it. It seem like maybe the schematics are incorrect, and what I think is the CS pin isn't really the CS pin, but I'm not sure how to verify I have the correct pin.
On my system the SPI device is "spidev0.2", which the documentation says means it is CS 2 on bus 0, which I'm not sure how to interpret. The schematics tell me it is ECSPI1_SS0/GPIO5_IO09 and physical pin 39. I'm not sure how that relates to CS 2 on bus 0.
Is there some way I can verify in Linux which pin is the SPI CS pin?
