[Intel-gfx] [PATCH 2/2] drm/i915: Add wait_for in init_ring_common

[Sean Paul]

I have seen a number of "blt ring initialization failed" messages
where the ctl or start registers are not the correct value. Upon further
inspection, if the code just waited a little bit, it would read the
correct value. Adding the wait_for to these reads should eliminate the
issue.

Signed-off-by: Sean Paul <seanpaul at chromium.org>
---
 drivers/gpu/drm/i915/intel_ringbuffer.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 8357822..d95f0f9 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -298,9 +298,9 @@ static int init_ring_common(struct intel_ring_buffer *ring)
 			| RING_REPORT_64K | RING_VALID);
 
 	/* If the head is still not zero, the ring is dead */
-	if ((I915_READ_CTL(ring) & RING_VALID) == 0 ||
-	    I915_READ_START(ring) != obj->gtt_offset ||
-	    (I915_READ_HEAD(ring) & HEAD_ADDR) != 0) {
+	if (wait_for((I915_READ_CTL(ring) & RING_VALID) != 0 &&
+		     I915_READ_START(ring) == obj->gtt_offset &&
+		     (I915_READ_HEAD(ring) & HEAD_ADDR) == 0, 50)) {
 		DRM_ERROR("%s initialization failed "
 				"ctl %08x head %08x tail %08x start %08x\n",
 				ring->name,
-- 
1.7.7.3