Re: [PATCH] drm/i915: Quirk the pipe A quirk in the modeset state checker

[Chris Wilson <chris@chris-wilson.co.uk>]

On Wed, May 29, 2013 at 10:41:29AM +0200, Daniel Vetter wrote:
> If we always force the pipe A to on we can't use the hw state to
> decide whether it should be on. Hence quirk the quirk.
> 
> The problem is that crtc->active tracks the state of the entire
> display pipe, i.e. including planes, encoders and all. But our hw
> state readout simply looks at the pipe. But with the pipe A quirk we
> force-enable that (together with it's pll). To fix that mismatch we
> have two options:
> - Quirk the checked state to match what our sw tracking states if the
>   pipe A quirk is in effect.
> - Improve the hw state readout to not get fooled by the pipe A quirk.
> 
> Since we already have similar state clamping in e.g. assert_pipe I've
> opted for the first variant. Also note that we don't really loose any
> state checking: Individual pieces of the abstract crtc pipe are
> checked in the enable/disable functions with the various asssert_*
> checks we have, and the hw state check code doesn't check anything if
> the pipe is off anyway.
> 
> v2: Pimp commit message after discussion with Chris and only apply the
> quirk for the quirk if we're checking pipe A. Otherwise we'll miss
> state checking for pipe B on i830M ...
> 
> v3: Make the code comment consistent with the improved commit message,
> too (Chris).
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=64764
> Cc: stable@vger.kernel.org
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Reported-and-Tested-by: mlsemon35@gmail.com (v1)
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre