[Intel-gfx] [PATCH 1/2] drm/i915: Add a partial instruction shootdown workaround on Broadwell.

[Kenneth Graunke]

I believe this will be necessary on production hardware.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 drivers/gpu/drm/i915/i915_reg.h | 3 +++
 drivers/gpu/drm/i915/intel_pm.c | 4 ++++
 2 files changed, 7 insertions(+)

I just realized tonight that my workarounds series never got merged.

After reviewing Ben and Chris's comments, I agree with all of them, so
I've dropped the unnecessary patches.  I also believe I shouldn't need
the pre-production workarounds I sent last time, so I've dropped those.

These two should apply to production hardware, so we probably want them.

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index ad75ff7..f36d5e0 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -5050,6 +5050,9 @@
 #define   GEN7_SINGLE_SUBSCAN_DISPATCH_ENABLE	(1<<10)
 #define   GEN7_PSD_SINGLE_PORT_DISPATCH_ENABLE	(1<<3)
 
+#define GEN8_ROW_CHICKEN		0xe4f0
+#define   PARTIAL_INSTRUCTION_SHOOTDOWN_DISABLE	(1<<8)
+
 #define GEN7_ROW_CHICKEN2		0xe4f4
 #define GEN7_ROW_CHICKEN2_GT2		0xf4f4
 #define   DOP_CLOCK_GATING_DISABLE	(1<<0)
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 4f01b04..df8ad21 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4838,6 +4838,10 @@ static void gen8_init_clock_gating(struct drm_device *dev)
 	/* FIXME(BDW): Check all the w/a, some might only apply to
 	 * pre-production hw. */
 
+	/* WaDisablePartialInstShootdown */
+	I915_WRITE(GEN8_ROW_CHICKEN,
+	           _MASKED_BIT_ENABLE(PARTIAL_INSTRUCTION_SHOOTDOWN_DISABLE));
+
 	/*
 	 * This GEN8_CENTROID_PIXEL_OPT_DIS W/A is only needed for
 	 * pre-production hardware
-- 
1.8.4.2