Comment 390 for bug 541511

> --- Comment #232 from Michal Nowak <email address hidden> 2010-08-30 02:38:12 PDT ---
> Daniel, could you be so kind and give us an update on this bug? From what I can
> see you created a decent patch which solves or enhances the situation for most
> of 855gm users but it seems that this patch did not make it upstream, is it
> correct? I also read on other approaches elsewhere: 1) dumping 855gm as
> unsupported, 2) reverting to user-mode setting... Thank You.

Ok, the long overdue status report: I haven't upstreamed the patch for a
few reasons:
- It's an extremely ugly approach, involving way too much duct-tape. Now
  if it would actually reliably work, but that's not the case.
- It has (under certain circumstances) rather severe performance
  implications (mostly because the eviction code is not clever enough).
Hence why I'm not satisfied and of the opinion that upstreaming might
cause more harm than good. Different story for distros, though.

I have a few ideas as how to amend this, but that requires a complete
rewrite of the gtt code. I've finally found time to start hacking on this,
see

http://cgit.freedesktop.org/~danvet/drm/log/?h=intel_gtt_rework

Don't try this on an i8xx, no cache coherency stuff in there (yet). I'll
give updates as soon as there is stuff to try out.

On other approaches for the short/medium term, as I seem them (take this
with a grain of salt, I'm just doing this for fun and leisure and I'm not
an Intel employee):

- Keep the old ums stuff around. Not supported by intel (and I don't think
  this will ever happen). You're basically on your own.
- Keep this patch as a band-aid. Thanksfully all the nice people here have
  been awesome with forward-porting and helping each another out, so this
  basically maintains itself ;)
- Chris Wilson's shadowfb branch. See

http://cgit.freedesktop.org/~ickle/xf86-video-intel/log/?h=shadow

  This won't give opengl, tough. But that looks like a good approach
  until the i8xx cache coherency nightmare is fixed for real. And it has
  the change of being merged to master.
- Burn your i855 on a pyre ;)

-Daniel