[Intel-gfx] [PATCH 2/2] drm/i915: Open-code i915_gpu_idle() for handling seqno wrapping

[Mika Kuoppala]

From: Chris Wilson <chris at chris-wilson.co.uk>

The complication is that during seqno wrapping we must be extremely
careful not to write to any ring as that will require a new seqno, and
so would recurse back into the seqno wrap handler. So we cannot call
i915_gpu_idle() as that does additional work beyond simply retiring the
current set of requests, and instead must do the minimal work ourselves
during seqno wrapping.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala at intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index e414507..e753cfc 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1938,11 +1938,15 @@ i915_gem_handle_seqno_wrap(struct drm_device *dev)
 	if (ret == 0)
 		return ret;
 
-	ret = i915_gpu_idle(dev);
-	if (ret)
-		return ret;
-
+	/* Carefully retire all requests without writing to the rings */
+	for_each_ring(ring, dev_priv, i) {
+		ret = intel_ring_idle(ring);
+		if (ret)
+			return ret;
+	}
 	i915_gem_retire_requests(dev);
+
+	/* Finally reset hw state */
 	for_each_ring(ring, dev_priv, i) {
 		ret = intel_ring_handle_seqno_wrap(ring);
 		if (ret)
-- 
1.7.9.5