OpenFirmware and Linux v5.0 on XO-1.75

[Lubomir Rintel]

Hi,

for the past few days I've been looking into updating the XO-1.75
OpenFirmware so that it's good enough to boot mainline Linux.

It now looks usable enough: the essentials such as simple framebuffer,
keyboard, Wi-Fi or USB all seem to work.

The branch's pretty large; counting 60 commits at the moment. Get it
from:

  git pull https://github.com/lkundrak/openfirmware lr/olpc-xo175-1

It's not done or finished (see the TODOs in many commits). Some
bindings are not settled in Linux tree. Howerver I still think it may
be a good idea to share it early to get some feedback and identify bits
that obviously stink.

I've tested it with the latest Fedora kernel [1] build (yay!) and also
booted the latest OLPC OS release. When booting the latter, there were
no differencies in "find /sys/devices -type d |sort" output, so I
assume the drivers that would use the device tree (there probably
aren't many) bind just fine.

[1] https://koji.fedoraproject.org/koji/buildinfo?buildID=1214041

I tried not to break other boards. olpc/4.0 still builds fine, but is
likely to end up with three clock nodes (/pmua, /apbc and /clocks).
olpc/3.0 was bitrotten before and I did not try doing x86 build, for
the most part I've been building natively on the XO-1.75.

For a x86_64 hosted build I needed to patch cforth. See [2]. The 
MitchBradley/cforth [1] master branch actually takes a similar
approach, but there the 1.75 support there seems severely bitrotten.

[2] https://github.com/lkundrak/cforth/commit/c88790fd32.patch
[3] https://github.com/MitchBradley/cforth

I didn't have the guts to actually flash and run the image built on
x86_64. I don't not seem to be able to program the spi flash by
attaching a soic8 clip to it, without unsoldering the chip and I don't
feel like doing that if I fuck things up.

At some point I'll hopefully follow up with something that could be
actually merged into the OpenFirmware, perhaps in a month or so. Until
then some more bindings may settle.

In particular, my hopes are that some of Armada DRM or EC may make it
into 5.1. Camera works, but needs some more love, perhaps 5.2.

Take care
Lubo