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drm/i915: preserve pipe A quirk in i9xx_set_pipeconf

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This regression has been introduced in

commit 9f11a9e4e50006b615ba94722dfc33ced89664cf
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Thu Jun 13 00:54:58 2013 +0200

    drm/i915: set up PIPECONF explicitly for i9xx/vlv platforms

Ville brough up the idea that this is just the pipe A quirk gone
wrong.

Note that after resume the bios might or might not have enabled pipe A
already.  We have a bit of magic to make sure that on resume we set up
a decent mode for pipe A, but I fear if I just smash pipe A to always
on we'd enable it in a bogus state and hang the hw. Hence the
readback.

v2: Clarify the logic a bit as suggested by Chris. Also amend the
commit message to clarify why we don't unconditionally enable the
pipe.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=66462
References: https://lkml.org/lkml/2013/8/26/238
Cc: Meelis Roos <mroos@ut.ee>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
[danvet: Use |= instead of = as suggested by Chris.]
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Daniel Vetter 2013-09-24 11:46:14 +02:00
parent 1062b81598
commit 67c72a1225
1 changed files with 4 additions and 0 deletions
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4
drivers/gpu/drm/i915/intel_display.c
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@ -4775,6 +4775,10 @@ static void i9xx_set_pipeconf(struct intel_crtc *intel_crtc)
pipeconf = 0;
if (dev_priv->quirks & QUIRK_PIPEA_FORCE &&
I915_READ(PIPECONF(intel_crtc->pipe)) & PIPECONF_ENABLE)
pipeconf |= PIPECONF_ENABLE;
if (intel_crtc->pipe == 0 && INTEL_INFO(dev)->gen < 4) {
/* Enable pixel doubling when the dot clock is > 90% of the (display)
* core speed.