Stuck on PS3 kernel

[Dan Munckton]

Hi kernel-team, ubuntu-cell,

Sorry for so long without news on PS3 stuff. I've come to a stage where
I need some help. I haven't really had any time to spend on PS3 work
recently and unfortunately I don't think this is likely to improve soon.

Trying to get the powerpc64-smp kernel flavour to work and remain
working on PS3 is proving to be a PITA (more detail below). I'm sure I
could eventually achieve it if I had time and better resources (e.g. a
muscular multicore G5).

I'm really concerned that I may be holding things up when there are
folks that may be better placed to work on this stuff. So from here I'd
like to suggest the following solutions in order to get anything to
happen for Intrepid on PS3, otherwise I can't guarantee much/any
progress from here.

1) I step back and someone with more kernel maintenance experience takes
over (if we can find someone to volunteer for that).

2) One or more less experienced volunteers work concurrently to fix
things. My role becomes integrator and reviewer - I keep my Git tree on
zinc [0] to make it easy to share changes with the Kernel Team until
these volunteers get their own Git trees on zinc. To help folks get up
and running quickly I've put some notes on my blog [1] on what to read,
syncing with upstream, and cross-compiling etc.

Whichever of the above directions we take I'm really becoming more and
more convinced that starting from scratch with a ps3_defconfig based
flavour would be quickest way to achieve a stable kernel.

Although ps3_defconfig is quite different to the Ubuntu kernel configs
(there are hundreds of modules enabled in Ubuntu that aren't in
ps3_defconfig) it always works - I observe a lot of the people happily
running newer versions of Ubuntu on PS3 have built their own custom
kernel based on this.

Once we have this flavour we can gradually begin re-enabling the
important modules (e.g. AppArmor), carefully avoiding those which cause
bugs or hangs. But at least we could then move on to fixing
installer/other issues. Opinions?


PROBLEMS USING POWERPC64-SMP FLAVOUR

These are the current problems with the powerpc64-smp kernel flavour on
PS3.

* As of 2.6.25.4 adding the patches/fixes we identified so far resulted
in a kernel which booted, allocated the correct amount of memory, but
hung on shutdown.

* After re-syncing to 2.6.25.16 we gained a new problem - it now hangs
on boot. The same problem is occurs with 2.6.27 using the same config.
Obviously there's yet more work to do to find out why and fix that
problem too (maybe a good few hours with git-bisect?). But using
ps3_defconfig it still works fine. If anyone wants to experiment my git
tree [0] has this broken version pushed to it.

* We can't use Cell specific optimisations. E.g. CONFIG_TUNE_CELL as
although it improves performance on Cell it degrades it on other power
chips [2].

Any input, ideas, or feedback greatly appreciated.

Cheers

Dan

[0]
http://kernel.ubuntu.com/git?p=dmunckton/ubuntu-intrepid-ports.git;a=summary
[1] http://munckfish.net/blog/categories/ps3/
[2] http://cateee.net/lkddb/web-lkddb/TUNE_CELL.html