drm/i915: Fix GT_MODE default value

commit f8f2ac9a76b0f80a6763ca316116a7bab8486997 upstream.

I can't even find how I figured this might be needed anymore. But sure
enough, the value I'm reading back on platforms doesn't match what the
docs recommends.

It seemed to fix Chris' GT1 in limited testing as well.

Tested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
[bwh: Backported to 3.2: open-code _MASKED_BIT_{ENABLE,DISABLE}]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index fec8df076baad235205fdd1a04cee00c69d5659e..a294a32c582a3cab7a112757635e2603636e3d9b 100644 (file)
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -401,6 +401,9 @@
 # define VS_TIMER_DISPATCH                             (1 << 6)
 # define MI_FLUSH_ENABLE                               (1 << 11)
 
+#define GEN6_GT_MODE   0x20d0
+#define   GEN6_GT_MODE_HI      (1 << 9)
+
 #define GFX_MODE       0x02520
 #define GFX_MODE_GEN7  0x0229c
 #define   GFX_RUN_LIST_ENABLE          (1<<15)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 8d5087eb0fb8f33c25afa5c3d48913e74d039078..adac0ddda7ceeee4010acd88084e69ec0d2be974 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8298,6 +8298,11 @@ static void gen6_init_clock_gating(struct drm_device *dev)
                           DISPPLANE_TRICKLE_FEED_DISABLE);
                intel_flush_display_plane(dev_priv, pipe);
        }
+
+       /* The default value should be 0x200 according to docs, but the two
+        * platforms I checked have a 0 for this. (Maybe BIOS overrides?) */
+       I915_WRITE(GEN6_GT_MODE, 0xffff << 16);
+       I915_WRITE(GEN6_GT_MODE, GEN6_GT_MODE_HI << 16 | GEN6_GT_MODE_HI);
 }
 
 static void gen7_setup_fixed_func_scheduler(struct drm_i915_private *dev_priv)