[PATCH] drm/intel: Set 8-bit gamma mode for the palette

[Peter Clifton <pcjc2@cam.ac.uk>]

We're programming an 8-bit palette, so ensure we set the hardware
up appropriately. Also, rename the palreg variable pal_reg for more
consistency with the rest of this file.
---
 drivers/gpu/drm/i915/intel_display.c |   16 ++++++++++++----
 1 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 4e5e688..006e5a5 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -3430,7 +3430,10 @@ void intel_crtc_load_lut(struct drm_crtc *crtc)
 	struct drm_device *dev = crtc->dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
-	int palreg = (intel_crtc->pipe == 0) ? PALETTE_A : PALETTE_B;
+	int pipe = intel_crtc->pipe;
+	int pal_reg = (pipe == 0) ? PALETTE_A : PALETTE_B;
+	int pipeconf_reg = (pipe == 0) ? PIPEACONF : PIPEBCONF;
+	int pipeconf = I915_READ(pipeconf_reg);
 	int i;
 
 	/* The clocks have to be on to load the palette. */
@@ -3439,11 +3442,16 @@ void intel_crtc_load_lut(struct drm_crtc *crtc)
 
 	/* use legacy palette for Ironlake */
 	if (IS_IRONLAKE(dev))
-		palreg = (intel_crtc->pipe == 0) ? LGC_PALETTE_A :
-						   LGC_PALETTE_B;
+		pal_reg = (intel_crtc->pipe == 0) ? LGC_PALETTE_A :
+						    LGC_PALETTE_B;
+
+	/* Switch to 8-bit gamma mode */
+	pipeconf &= ~PIPEACONF_GAMMA;
+	I915_WRITE(pipeconf_reg, pipeconf);
+	I915_READ(pipeconf_reg);
 
 	for (i = 0; i < 256; i++) {
-		I915_WRITE(palreg + 4 * i,
+		I915_WRITE(pal_reg + 4 * i,
 			   (intel_crtc->lut_r[i] << 16) |
 			   (intel_crtc->lut_g[i] << 8) |
 			   intel_crtc->lut_b[i]);
-- 
1.7.0.4