Re: [PATCH 00/30] drm/i915: Lots of workaround changes

Ville Syrjälä
2013-07-05T20:03:14Z

On Fri, Jul 05, 2013 at 12:51:54PM -0700, Ben Widawsky wrote:
> On Fri, Jul 05, 2013 at 04:48:18PM +0300, ville.syrjala@linux.intel.com wrote:
> > I was going over the workaround database with VLV mainly in mind, but I
> > ended up stumbling on quite a few others as well.
> >
> > This series adds the workarounds names in a bunch of places where we
> > missed them, adds a few workarounds we seem to have missed, drops some
> > that were never supposed to be there, and drops quite a few pre-production
> > workarounds.
> >
> > I'm not sure we want to drop some of the VLV workarounds quite yet. I know
> > Jani will hate me when he comes back from vacation since his current machine
> > would be affected.
> >
> > I've run these on my VLV and IVB machines, and didn't spot any problems.
> > The SNB and HSW ones I've not actually tested.
>
> I have a sneaking suspicion at least a few of these will blow up once
> their in the wild. You're trusting the docs an awful lot. At least the
> patches seem quite bisectable though, so that's a saving grace.

Yeah I wanted to keep them as isolated as possible just for that reason.

> One thing which might be interesting/compelling is some performance data
> (especially around places where you've removed unneeded workarounds).

Some power consumption numbers migth be nice, since quite a few are
clock gating related.

There are plenty of options to deal with the risk:
- Throw the patches away and pretend they never existed
- Merge them all and watch out for fireworks
- Drop a few of them into every kernel release to avoid too
many regressions at once. I guess it'll take a few years
get through the list this way.

--
Ville Syrjälä
Intel OTC