CHERRY-PICK: drm/i915: Add wait_for in init_ring_common

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@chromium.org>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
(cherry picked from commit f01db988ef6f6c70a6cc36ee71e4a98a68901229)

TEST=Tested on lumpy with 1000's of suspend/resume cycles
BUG=chrome-os-partner:8366

Change-Id: I9544a5a65efb0775302ccf001d4dc1b43a429963
Reviewed-on: https://gerrit.chromium.org/gerrit/18459
Tested-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Grant Grundler <grundler@chromium.org>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
Commit-Ready: Sean Paul <seanpaul@chromium.org>

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 62892a8..60ff6f0 100644 (file)
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -290,9 +290,9 @@ static int init_ring_common(struct intel_ring_buffer *ring)
                        | 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,