On Tue, 24 Dec 2024 at 14:00, Gijs Peskens gijs.peskens@munisense.com wrote:
I'm working on getting a compute module working with Yocto using U-Boot as bootloader, which mostly works thanks to previous work to get RPi 5 working. However I'm running into a strange issue: if I turn on the CM5 without the debug UART (which requires soldering a header onto the CM5) attached, the Pi doesn't boot beyond showing the submarine splash screen, if I boot it with the console attached it autoboots correctly. If I attach the UART after the boot halted and press enter I get a U-Boot console, and giving the boot command boots it normally. And setting bootdelay=-2 in the env allows it to correctly boot.
Which leads me to believe there is perhaps a spurious input registered by U-Boot which interrupts autobooting.
Is there a command that allows me to extract why U-Boot didn't continue autobooting?
And anyone have a hint how this could perhaps be fixed in a more elegant way (allowing interruptable autoboot).
The hardware I'm testing on is the CM5 devkit, I needed to make small changes to yocto to get it working: https://github.com/agherzan/meta-raspberrypi/pull/1397
I don't think this is unique to the CM5, I've seen it on other RPi models, I have a RPi4 8Gb model that exhibits the same behavior, yet other RPi4s I have don't exhibit the behavious. In the case of the 8Gb I have a USB serial TTL on it, it boots if the USB is plugged in, doesn't if not. I have other v4s, both with and without the TTL and they boot fine, I've never been able to get to the bottom of why.