Re: [PATCH 4/6] drm/i915: simplify i915_reset a bit

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Wed, 25 Apr 2012 22:27:12 +0200
Daniel Vetter <daniel@ffwll.ch> wrote:

> On Wed, Apr 25, 2012 at 09:18:21AM -0700, Jesse Barnes wrote:
> > On Wed, 25 Apr 2012 13:57:11 +0200
> > Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> > 
> > > - need_display is always true, scrap it.
> > > - don't reacquire the mutex to do nothing after having restored the
> > >   gem state.
> > > 
> > 
> > Actually I think we generally *don't* need to reset display.  It's
> > currently there just because we haven't tried reset handling without
> > it.  But not resetting display would make resets a little less visible,
> > which would be nice.  Now that you have a nice test setup, can you try
> > testing without the display engine bit set (i.e. only reset render and
> > media at hang time)?
> 
> Imo 'less visible' and gpu hang don't go well together, the 3 second
> freeze plus screen flicker at least ensure that users report bugs. And I
> have no idea whether resetting the entire gpu or just the render portion
> has a greater chance of survival. So I'm not sure whether working on this
> has much benefit ... at least opposed to working on the bugs ;-)

With the CPU/PCH split, display reset is actually a really big hammer.
Theoretically, just doing a render/media reset will be more reliable
and have less chance of wedging the system really hard.

-- 
Jesse Barnes, Intel Open Source Technology Center