Possible RPI4 Documentation Regression with `dtoverlay=disable-bt` and `serial0` kernel patch.

[IridescentRose]

Hello, I've been having an issue with running sel4test according to the updated documentation, and shared my findings on the sel4 Discourse.

Expected Behavior: config.txt without the dtoverlay=disable-bt allows u-boot.bin to load on Raspberry Pi 4B 4GB.
Actual Behavior: u-boot.bin does not load.

Solution: Re-adding the line dtoverlay=disable-bt causes u-boot to load and get to the next phase, which is running sel4test on the PI 4B

Secondary issue:
Expected Behavior: Running sel4test with go 0x10000000 shows the testing over UART on serial0
Actual Behavior: No output is observed

Solution: Implementing the kernel patch mentioned in this revision of the documentation yields the sel4test outputting as expected and succeeding all tests over the UART on serial0

I'd be more than happy to continue discussion, contribute a PR to the documentation or kernel if necessary. Thank you!

[Ivan-Velickovic]

Hi, thanks for posting your issue.

I was the one who removed those instructions in the documentation as I saw them unnecessary and I was able to get a Raspberry Pi 4B working without them.

What's weird is that I've seen one person who hasn't actually been able to run seL4 with the dtoverlay=disable-bt line in their config.txt.

I wish this hardware platform wasn't so fragile. I don't have access to a Raspberry Pi right now but will get back to you next week.

[IridescentRose]

Thank you for your response! I'm not exactly sure what the reason for this strange behavior might be, but one of the things I'm thinking could be a possibility is different firmware versions; I bought a new Pi 4B to try seL4 on, and this Pi has never had its firmware upgraded nor installed Raspbian on it. I will try to provide exact firmware versions, update the Pi, and then retry the steps in the tutorial tonight.

[Ivan-Velickovic]

Sure thing. Another thing we can do is send you a zip of everything on my SD card and see if that works for you, it may help rule out some issues.

[IridescentRose]

That sounds good - I'd be willing to try that first; My contact email is iridescentrosesfall@gmail.com