[Intel-gfx] [PATCH 1/4] drm/i915/bdw: Implement non-coherent ctx w/a

[Ben Widawsky]

Implements a required workaround whose implications aren't entirely clear to me
from the description. In particular I do not know if this effects legacy
contexts, execlists, or both.

I couldn't find a real workaround name, so I made up:
WaHdcCtxNonCoherent

Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
---
 drivers/gpu/drm/i915/i915_reg.h         | 5 +++--
 drivers/gpu/drm/i915/intel_ringbuffer.c | 2 ++
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 0f32fd1a..dabac96 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -5219,9 +5219,10 @@ enum punit_power_well {
 
 /* GEN8 chicken */
 #define HDC_CHICKEN0				0x7300
-#define  HDC_FORCE_NON_COHERENT			(1<<4)
-#define  HDC_DONOT_FETCH_MEM_WHEN_MASKED	(1<<11)
 #define  HDC_FENCE_DEST_SLM_DISABLE		(1<<14)
+#define  HDC_DONOT_FETCH_MEM_WHEN_MASKED	(1<<11)
+#define  HDC_FORCE_CTX_NON_COHERENT		(1<<5)
+#define  HDC_FORCE_NON_COHERENT			(1<<4)
 
 /* WaCatErrorRejectionIssue */
 #define GEN7_SQ_CHICKEN_MBCUNIT_CONFIG		0x9030
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 12a36f0..62318a4 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -790,8 +790,10 @@ static int bdw_init_workarounds(struct intel_engine_cs *ring)
 	 */
 	/* WaForceEnableNonCoherent:bdw */
 	/* WaHdcDisableFetchWhenMasked:bdw */
+	/* WaHdcCtxNonCoherent:bdw */
 	/* WaDisableFenceDestinationToSLM:bdw (GT3 pre-production) */
 	WA_SET_BIT_MASKED(HDC_CHICKEN0,
+			  HDC_FORCE_CTX_NON_COHERENT |
 			  HDC_FORCE_NON_COHERENT |
 			  HDC_DONOT_FETCH_MEM_WHEN_MASKED |
 			  (IS_BDW_GT3(dev) ? HDC_FENCE_DEST_SLM_DISABLE : 0));
-- 
2.2.1