[PATCH 1/2] drm/i915: enable HiZ Raw Stall Optimization on HSW

[Chia-I Wu <olvaffe@gmail.com>]

From: Chia-I Wu <olv@lunarg.com>

The optimization is available on Ivy Bridge and later, and is disabled by
default.  Enabling it helps certain workloads such as GLBenchmark TRex test.

No piglit regression.

v2
 - no need to save the register before suspend as init_clock_gating can
   correctly program it after resume
 - split IVB change to another commit

Signed-off-by: Chia-I Wu <olv@lunarg.com>
---
 drivers/gpu/drm/i915/i915_reg.h | 2 ++
 drivers/gpu/drm/i915/intel_pm.c | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 76126e0..c74bc28 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -934,6 +934,8 @@
 #define   ECO_GATING_CX_ONLY	(1<<3)
 #define   ECO_FLIP_DONE		(1<<0)
 
+#define CACHE_MODE_0_GEN7	0x7000 /* IVB+ */
+#define   HIZ_RAW_STALL_OPT_DISABLE (1<<2)
 #define CACHE_MODE_1		0x7004 /* IVB+ */
 #define   PIXEL_SUBSPAN_COLLECT_OPT_DISABLE (1<<6)
 
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index d77cc81..c535e5c 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4789,6 +4789,10 @@ static void haswell_init_clock_gating(struct drm_device *dev)
 	/* WaVSRefCountFullforceMissDisable:hsw */
 	gen7_setup_fixed_func_scheduler(dev_priv);
 
+	/* enable HiZ Raw Stall Optimization */
+	I915_WRITE(CACHE_MODE_0_GEN7,
+		   _MASKED_BIT_DISABLE(HIZ_RAW_STALL_OPT_DISABLE));
+
 	/* WaDisable4x2SubspanOptimization:hsw */
 	I915_WRITE(CACHE_MODE_1,
 		   _MASKED_BIT_ENABLE(PIXEL_SUBSPAN_COLLECT_OPT_DISABLE));
-- 
1.8.3.1