drm/i915: preserve the PBC bits of TRANS_CHICKEN2

Bits 30 and 24:0 are PBC, so don't zero them. Some of the other bits
are being zeroed, but I couldn't find a reason for this, so leave them
as they are for now to avoid regressions.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
[danvet: Delete the redudant #define that Imre spotted in his review.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

2 files changed, 11 insertions, 3 deletions

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index fc8a4a940e92..31de7e4b1f3e 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -3959,8 +3959,11 @@
 #define _TRANSA_CHICKEN2         0xf0064
 #define _TRANSB_CHICKEN2         0xf1064
 #define TRANS_CHICKEN2(pipe) _PIPE(pipe, _TRANSA_CHICKEN2, _TRANSB_CHICKEN2)
-#define  TRANS_CHICKEN2_TIMING_OVERRIDE         (1<<31)
-#define  TRANS_CHICKEN2_FDI_POLARITY_REVERSED   (1<<29)
+#define  TRANS_CHICKEN2_TIMING_OVERRIDE                 (1<<31)
+#define  TRANS_CHICKEN2_FDI_POLARITY_REVERSED           (1<<29)
+#define  TRANS_CHICKEN2_FRAME_START_DELAY_MASK          (3<<27)
+#define  TRANS_CHICKEN2_DISABLE_DEEP_COLOR_COUNTER      (1<<26)
+#define  TRANS_CHICKEN2_DISABLE_DEEP_COLOR_MODESWITCH   (1<<25)
 
 #define SOUTH_CHICKEN1          0xc2000
 #define  FDIA_PHASE_SYNC_SHIFT_OVR      19
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 6f67fa122f81..e34ad9642519 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3604,9 +3604,14 @@ static void cpt_init_clock_gating(struct drm_device *dev)
          * downward, on (only) LVDS of some HP laptops with IVY.
          */
         for_each_pipe(pipe) {
-                val = TRANS_CHICKEN2_TIMING_OVERRIDE;
+                val = I915_READ(TRANS_CHICKEN2(pipe));
+                val |= TRANS_CHICKEN2_TIMING_OVERRIDE;
+                val &= ~TRANS_CHICKEN2_FDI_POLARITY_REVERSED;
                 if (dev_priv->fdi_rx_polarity_inverted)
                         val |= TRANS_CHICKEN2_FDI_POLARITY_REVERSED;
+                val &= ~TRANS_CHICKEN2_FRAME_START_DELAY_MASK;
+                val &= ~TRANS_CHICKEN2_DISABLE_DEEP_COLOR_COUNTER;
+                val &= ~TRANS_CHICKEN2_DISABLE_DEEP_COLOR_MODESWITCH;
                 I915_WRITE(TRANS_CHICKEN2(pipe), val);
         }
         /* WADP0ClockGatingDisable */