[Intel-gfx] [PATCH 6/7] drm/i915: BDW Semaphore signal with Post Sync

[Rodrigo Vivi]

With this bit set MI_SEMAPHORE_SIGNAL command is executed as a pipelined
PIPE_CONTROL flush command with Semaphore Signal as post sync operation.
However this can only be set only when "Fixed Function DOP Clock Gate Disable"
is set.

This brought a bit of stability on Semaphores minimizing the hangs.

Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h         | 1 +
 drivers/gpu/drm/i915/intel_pm.c         | 3 +++
 drivers/gpu/drm/i915/intel_ringbuffer.c | 1 +
 3 files changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index dc13961..27a54a0 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -269,6 +269,7 @@
 #define MI_SEMAPHORE_SIGNAL	MI_INSTR(0x1b, 0) /* GEN8+ */
 #define   MI_SEMAPHORE_TARGET(engine)	((engine)<<15)
 #define MI_SEMAPHORE_WAIT	MI_INSTR(0x1c, 2) /* GEN8+ */
+#define   MI_SEMAPHORE_POST_SYNC	(1<<21)
 #define   MI_SEMAPHORE_POLL		(1<<15)
 #define   MI_SEMAPHORE_SAD_GTE_SDD	(1<<12)
 #define MI_STORE_DWORD_IMM	MI_INSTR(0x20, 1)
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index f919596..ab8cbda 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -5481,6 +5481,9 @@ static void gen8_init_clock_gating(struct drm_device *dev)
 	I915_WRITE(GEN6_RC_SLEEP_PSMI_CONTROL,
 		   _MASKED_BIT_ENABLE(GEN8_RC_SEMA_IDLE_MSG_DISABLE));
 
+	I915_WRITE(GEN6_RC_SLEEP_PSMI_CONTROL,
+		   _MASKED_BIT_ENABLE(GEN8_FF_DOP_CLOCK_GATE_DISABLE));
+
 	/* WaDisableSDEUnitClockGating:bdw */
 	I915_WRITE(GEN8_UCGCTL6, I915_READ(GEN8_UCGCTL6) |
 		   GEN8_SDEUNIT_CLOCK_GATE_DISABLE);
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index cd30b39..edb8234 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -730,6 +730,7 @@ static int gen8_rcs_signal(struct intel_engine_cs *signaller,
 		intel_ring_emit(signaller, signaller->outstanding_lazy_seqno);
 		intel_ring_emit(signaller, 0);
 		intel_ring_emit(signaller, MI_SEMAPHORE_SIGNAL |
+					   MI_SEMAPHORE_POST_SYNC |
 					   MI_SEMAPHORE_TARGET(waiter->id));
 		intel_ring_emit(signaller, 0);
 	}
-- 
1.9.3