[PATCH 2/2] drm/i915: Apply display workaround required according to the B-Spec.

[Eric Anholt <eric@anholt.net>]

Not known to fix any current bugs.

Signed-off-by: Eric Anholt <eric@anholt.net>
---
 drivers/gpu/drm/i915/i915_reg.h      |    2 ++
 drivers/gpu/drm/i915/intel_display.c |    4 ++++
 2 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index f338499..308f0a9 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -2599,6 +2599,8 @@
 #define GTIER   0x4401c
 
 #define ILK_DISPLAY_CHICKEN2	0x42004
+/* Required on all Ironlake and Sandybridge according to the B-Spec. */
+#define  ILK_ELPIN_409_SELECT	(1 << 25)
 #define  ILK_DPARB_GATE	(1<<22)
 #define  ILK_VSDPFD_FULL	(1<<21)
 #define ILK_DSPCLK_GATE		0x42020
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 360f17d..8f564ce 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -5813,6 +5813,10 @@ void intel_init_clock_gating(struct drm_device *dev)
 				   ILK_CLK_FBC);
 		}
 
+		I915_WRITE(ILK_DISPLAY_CHICKEN2,
+			   I915_READ(ILK_DISPLAY_CHICKEN2) |
+			   ILK_ELPIN_409_SELECT);
+
 		if (IS_GEN5(dev)) {
 			I915_WRITE(_3D_CHICKEN2,
 				   _3D_CHICKEN2_WM_READ_PIPELINED << 16 |
-- 
1.7.2.3