[PATCH] drm/i915: stop command parser before sync flush

[naresh.kumar.kachhi@intel.com]

From: Naresh Kumar Kachhi <naresh.kumar.kachhi@intel.com>

Based on Bspec the command parser must be stopped prior to
issuing sync flush. Only after observing Rings Idle set in
MI_MODE can a Sync Flush be issued. Once sync flush has
finished the command parser is re-enabled by clearing Stop Rings.

Signed-off-by: Naresh Kumar Kachhi <naresh.kumar.kachhi@intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h         |  3 +++
 drivers/gpu/drm/i915/intel_ringbuffer.c | 13 +++++++++++++
 drivers/gpu/drm/i915/intel_ringbuffer.h |  5 +++++
 3 files changed, 21 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 2f564ce..97d872a 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -720,6 +720,7 @@
 #define RING_INSTPS(base)	((base)+0x70)
 #define RING_DMA_FADD(base)	((base)+0x78)
 #define RING_INSTPM(base)	((base)+0xc0)
+#define RING_MI_MODE(base)	((base)+0x9c)
 #define INSTPS		0x02070 /* 965+ only */
 #define INSTDONE1	0x0207c /* 965+ only */
 #define ACTHD_I965	0x02074
@@ -796,6 +797,8 @@
 # define VS_TIMER_DISPATCH				(1 << 6)
 # define MI_FLUSH_ENABLE				(1 << 12)
 # define ASYNC_FLIP_PERF_DISABLE			(1 << 14)
+# define MODE_STOP					(1 << 8)
+# define MODE_IDLE					(1 << 9)
 
 #define GEN6_GT_MODE	0x20d0
 #define   GEN6_GT_MODE_HI				(1 << 9)
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index b340c75..477b5dc 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -982,6 +982,15 @@ void intel_ring_setup_status_page(struct intel_ring_buffer *ring)
 	/* Flush the TLB for this page */
 	if (INTEL_INFO(dev)->gen >= 6) {
 		u32 reg = RING_INSTPM(ring->mmio_base);
+
+		/* before issuing a sync flush request the ring to go idle */
+		I915_WRITE_MODE(ring, _MASKED_BIT_ENABLE(MODE_STOP));
+
+		/* Wait for idle */
+		if (wait_for_atomic((I915_READ_MODE(ring) & MODE_IDLE) != 0, 1000))
+			/* don't fail here, try to invalidate TLB */
+			DRM_ERROR("%s :timed out trying to stop ring", ring->name);
+
 		I915_WRITE(reg,
 			   _MASKED_BIT_ENABLE(INSTPM_TLB_INVALIDATE |
 					      INSTPM_SYNC_FLUSH));
@@ -989,6 +998,10 @@ void intel_ring_setup_status_page(struct intel_ring_buffer *ring)
 			     1000))
 			DRM_ERROR("%s: wait for SyncFlush to complete for TLB invalidation timed out\n",
 				  ring->name);
+
+		/* Clear the MI_MODE stop bit */
+		I915_WRITE_MODE(ring, _MASKED_BIT_DISABLE(MODE_STOP));
+		reg = I915_READ_MODE(ring);    /* Barrier read */
 	}
 }
 
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 08b91c6..1bb4a01 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -33,6 +33,11 @@ struct  intel_hw_status_page {
 #define I915_READ_IMR(ring) I915_READ(RING_IMR((ring)->mmio_base))
 #define I915_WRITE_IMR(ring, val) I915_WRITE(RING_IMR((ring)->mmio_base), val)
 
+#define I915_READ_MODE(ring) \
+	I915_READ(RING_MI_MODE((ring)->mmio_base))
+#define I915_WRITE_MODE(ring, val) \
+	I915_WRITE(RING_MI_MODE((ring)->mmio_base), val)
+
 enum intel_ring_hangcheck_action {
 	HANGCHECK_IDLE = 0,
 	HANGCHECK_WAIT,
-- 
1.8.1.2