[Intel-gfx] [PATCH] drm/i915: rip out the HWSTAM missed irq workaround

[Daniel Vetter]

On Mon, Jan 09, 2012 at 02:00:47PM -0800, Keith Packard wrote:
> On Thu,  5 Jan 2012 23:11:53 +0100, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> 
> > With the new ducttape of much finer quality, this seems to be no
> > longer necessary.
> > 
> > Tested on my ivb and snb machine with the usual suspects of testcases.
> 
> Eric suggested that unless we have evidence that the new work-around
> fixes bugs on SNB, that we should continue to use the HWSTAM work-around
> on that chip and use the RC6 voodoo on IVB, thus not potentially causing
> regressions on SNB.
> 
> For back-porting to older kernels, that's obviously the right plan. I
> think it's also the right plan for newer kernels, but I'd love to hear
> alternate views on the matter.

I honestly don't trust my patch, so I'd like to give it as much validation
as possible. Which means:
- Shove it into -next and beat on it there. We can ship current 3.3 with
  Eric's workaround - it's not great but at least this works.
- Enable the voodoo and revert the HWSTAM w/a also on snb - there are
  orders more snb machines in the wild than pre-production ivbs. I.e. this
  hopefully greatly increases our changes to find out whether the voodoo
  really works or if it is only pretty decent, but not perfect ducttape.
- See what happens and act accordingly (maybe reinstate the HWSTAM w/a if
  it's required). If things really work out when this hits mainline,
  backport the voodoo patch, leaving the HWSTAM in place for older
  kernels.

Yep, I'm officially paranoid about this ;-) rc6, forcewake and friends
have simply blown up too often in unpredictable ways ...
-Daniel
-- 
Daniel Vetter
Mail: daniel at ffwll.ch
Mobile: +41 (0)79 365 57 48