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>
Signed-off-by: Julien Cristau <jcristau@debian.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 06c0fc3dcd63a5ec3d54925948d61fd0a6fd5b4f..27a296a1415e1939610f5e1cf088ce3b00237d6f 100644 (file)
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -445,6 +445,9 @@
 # define VS_TIMER_DISPATCH                             (1 << 6)
 # define MI_FLUSH_ENABLE                               (1 << 12)
 
+#define GEN6_GT_MODE   0x20d0
+#define   GEN6_GT_MODE_HI      (1 << 9)
+
 #define GFX_MODE       0x02520
 #define GFX_MODE_GEN7  0x0229c
 #define RING_MODE_GEN7(ring)   ((ring)->mmio_base+0x29c)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index db780cbad99794de2c4ea61e69515a9104691edf..db2163f2e3280c814a376fc2bcdbfc96e2bc9195 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8620,6 +8620,11 @@ 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)