Re: [PATCH] drm/i915: paper over missed irq issues with force wake vodoo

[Daniel Vetter <daniel@ffwll.ch>]

On Sat, Jan 14, 2012 at 12:52:31AM +0100, Daniel Vetter wrote:
> On Fri, Jan 13, 2012 at 08:42:00AM -0800, Keith Packard wrote:
> > On Wed,  4 Jan 2012 19:40:45 +0100, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> > 
> > > Two things seem to do the trick on my ivb machine here:
> > > - prevent the gt from powering down while waiting for seqno
> > >   notification interrupts by grabbing the force_wake in get_irq (and
> > >   dropping it in put_irq again).
> > > - ordering writes from the ring's CS by reading a CS register, ACTHD
> > >   seems to work.
> > 
> > I've rebased this code on top of drm-intel-fixes and pushed it to my
> > forcewake-spinlock branch. I'd like to get this pushed to
> > drm-intel-fixes in the next couple of days, get some QA coverage and
> > then get it merged to master so that we can get some community testing
> > early in the 3.3 cycle.
> 
> A few quick comments:
> - I think we need to amend the commit msg of the voodoo patch with the
>   piece of doc I've discovered. If you want I can send out a v3 with that.
> - I think the HWSTAM revert is material for -next
> - Can you post your 3 patches on intel-gfx, I think I can shoot at them a
>   bit ;-)
> 
> acc101d drm/i915: Hold gt_lock across forcewake register reads
> 
> Imo this is a simple cleanup (reading forcewake-protected registers isn't
> really a fast-path for us), so material for -next.
> 
> 0f0e134 drm/i915: Hold gt_lock during reset
> 
> I still don't see what race you're trying to protect here, after all the
> gpu just died, things are confusing anyway (and anyone accessing the gpu
> in such a state should take that into account). Currently that's no one
> afaics. So imo at most -next material.
> 
> 176b987 drm/i915: Move reset forcewake processing to gen6_do_reset
> 
> Again this is imo just a cleanup. Furthermore the commit msg is lying a
> bit because it fails to mention the fix to use the forcewake function
> pointer. So the cleanup is imo for -next and the bugfix is really old,
> see:

Meh, mutt mail fail, I've hit the wrong key when I've tried to look up the
reference for that patch mail. Here we go:

http://lists.freedesktop.org/archives/intel-gfx/2011-November/013668.html

And the resend:

http://www.mail-archive.com/intel-gfx@lists.freedesktop.org/msg07229.html

Yours, Daniel
-- 
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48