[Intel-gfx] [PATCH] drm/i915: Fixed VS thread distribution between slices

[Ben Widawsky]

From: "bernard.r.kilarski" <your-user-name at intel.com>

Full disclosure: my IVB hangs on nexuiz both before, and after this patch, and
I haven't done any debug

This patch was given to me by Bernard, by way of Daniel. The patch came
with very little description, and I haven't really spent too much time
in the spec to make much sense out of it.

The improvement (IVB only) with my nexuiz configuration is almost
unbelievable. It has a more humble improvement on OpenArena. I'll throw
other tests at it, and try to debug the hangs a bit, but given the
nexuiz results, I was compelled to post this sooner, rather than later.

I see about a 2% improvement on OA
and about a 40$% improvement on nexuiz

CC: Daniel Vetter <daniel.vetter at ffwll.ch>
Signed-off-by: Ben Widawsky <benjamin.widawsky at intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h      |    3 +++
 drivers/gpu/drm/i915/intel_display.c |    3 +++
 2 files changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index cb55444..755bdff 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -682,6 +682,9 @@
 
 #define GEN6_BSD_RNCID			0x12198
 
+#define GEN7_FF_THREAD_MODE		0x20a0
+#define GEN7_FF_THREAD_SIMPLE_SCHED	0x28a00010
+
 /*
  * Framebuffer compression (915+ only)
  */
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 6ec81b4..bbd5f46 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8893,6 +8893,9 @@ static void ivybridge_init_clock_gating(struct drm_device *dev)
 			   DISPPLANE_TRICKLE_FEED_DISABLE);
 		intel_flush_display_plane(dev_priv, pipe);
 	}
+
+	/* Fix vertex load balancing */
+	I915_WRITE(GEN7_FF_THREAD_MODE,GEN7_FF_THREAD_SIMPLE_SCHED);
 }
 
 static void valleyview_init_clock_gating(struct drm_device *dev)
-- 
1.7.10