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drm/i915: Fix shifted screen on top of LVDS on IVY laptop 

The commit [23670b322: drm/i915: CPT+ pch transcoder workaround]
caused a regression on some HP laptops with IvyBridge.  The whole
laptop screen is shifted downward for a few pixels constantly.
The problem appears only on LVDS while DP and VGA seem unaffected.
Also, the problem disappears once when go and back from S3.
(S4 resume still shows the same problem.)

This patch revives the minimum part the commit above dropped.
For fixing this regression, only the setup of CHICKEN2 bit in
cpt_init_clock_gating() is needed.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Takashi Iwai 2012-12-11 11:46:29 +01:00 committed by Daniel Vetter
parent 539526b413
commit 335c07b798
1 changed files with 5 additions and 0 deletions
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5
drivers/gpu/drm/i915/intel_pm.c
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@ -3453,6 +3453,11 @@ static void cpt_init_clock_gating(struct drm_device *dev)
I915_WRITE(SOUTH_DSPCLK_GATE_D, PCH_DPLSUNIT_CLOCK_GATE_DISABLE);
I915_WRITE(SOUTH_CHICKEN2, I915_READ(SOUTH_CHICKEN2) |
DPLS_EDP_PPS_FIX_DIS);
/* The below fixes the weird display corruption, a few pixels shifted
* downward, on (only) LVDS of some HP laptops with IVY.
*/
for_each_pipe(pipe)
I915_WRITE(TRANS_CHICKEN2(pipe), TRANS_CHICKEN2_TIMING_OVERRIDE);
/* WADP0ClockGatingDisable */
for_each_pipe(pipe) {
I915_WRITE(TRANS_CHICKEN1(pipe),