This regression has been introduced in
commit 9f11a9e4e50006b615ba94722dfc33ced89664cf
Author: Daniel Vetter <daniel.vetter@xxxxxxxx>
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@xxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
---
drivers/gpu/drm/i915/intel_display.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index d8a1d98..6040b00 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -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.
--
1.8.4.rc3
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