Raspberry Pi 3 64-bit kernel

[Ryan Finnie]

The raspi2 kernel works fine on the Raspberry Pi 3 in 32-bit mode, but 64-bit mode is also an option. I've currently got a test setup using xenial arm64 userland + updated firmware/u-boot + the 4.5.0 kernel from someone who made a Debian image a month ago (http://www.tom-yam.or.jp/rpi3/rpi3-arm64-debian-20160414.img.xz), but I don't see any information about the source tree he used to compile it. Presumably https://github.com/raspberrypi/linux/tree/rpi-4.5.y; I'll see if I can reproduce with his config (attached). Hopefully the same kernel tree can be used for (raspi2 32-bit & raspi3 32-bit) and (raspi3 64-bit).

[Ryan Finnie (fo0bar)]

Looks like the kernel in that image was sourced from https://github.com/Electron752/boot64-rpi3, built from https://github.com/Electron752/linux .

[Paolo Pisati (p-pisati)]

Interesting - he puts the arm64 bits on top of an old rpi-4.5.y branch (~4.5-rc7, no tag unfortunately) - i tried to contact him to see where he got the arm64 code or if he wrote if by himself, let's see if he follows up.

[Paolo Pisati (p-pisati)]

Ok, never mind, the author of that kernel is unreachable:

Delivery to the following recipient failed permanently:

     <email address hidden>

Technical details of permanent failure:
DNS Error: 23722983 DNS type 'mx' lookup of crowfest.net responded with code NOERROR
23722983 DNS type 'mx' lookup of crowfest.net had no relevant answers.
23722983 DNS type 'aaaa' lookup of crowfest.net responded with code NOERROR
23722983 DNS type 'aaaa' lookup of crowfest.net had no relevant answers.
23722983 DNS type 'a' lookup of crowfest.net responded with code NOERROR
23722983 DNS type 'a' lookup of crowfest.net had no relevant answers.
...

[Ryan Finnie (fo0bar)]

Yeah sorry, meant to loop back on this. His kernel is minimally functional and I've been using it on a test arm64 machine (though looks like vchiq is intentionally disabled presumably because it's not functional, and the brcmfmac module doesn't recognize the wifi chipset even with firmware present), but it looks like it is a very early one-off effort.

We do eventually want to have RPi3 arm64 support, but it's probably not going to happen for awhile. Interestingly, the Raspbian kernel trees show no work toward arm64 support; hopefully they're just working on it in the background.

[Tianon Gravi (tianon)]

I think https://github.com/raspberrypi/firmware/issues/550 has some relevant information, especially https://github.com/raspberrypi/firmware/issues/550#issuecomment-190780010 (RPi Foundation is not working on arm64) and https://github.com/raspberrypi/firmware/issues/550#issuecomment-197452521 (which points to some community members that are making good progress).