On 2021/04/20 00:46, Alessandro Pistocchi wrote: > Hi, > > I am playing around with openbsd kernel source code on a raspberry pi 4. > > I have a couple of questions: > Does openbsd use low or high peripheral mode? > At what virtual address does openbsd map the peripheral base address ? > > I had a look at the source code but that part is still a bit cryptic for me. > > Thank you, > Alessandro
I can give you some pointers that will give you some places to start digging, but not answer everything: https://github.com/raspberrypi/firmware/issues/1374#issuecomment-617628570 suggests that this must be set by the video controller (which is used to boot the main CPU), and that it's done automatically on newer firmware depending on the device tree used. You can display the device tree used with "eeprom -p". If you're using U-Boot (included for rpi4 on recent snapshots/images) then the device trees are provided by OpenBSD and currently come from Linux 5.11 (via the sysutils/dtb port) where it looks like they're low. If you're using the UEFI firmware then the device trees are supplied with it, I haven't checked but I guess those are probably low too.
