[Intel-gfx] [PATCH 05/12 v2] drm/i915: drop polled waits from i915_wait_request

[Ben Widawsky]

The only time irq_get should fail is during unload or suspend. Both of
these points should try to quiesce the GPU before disabling interrupts
and so the atomic polling should never occur.

This was recommended by Chris Wilson as a way of reducing added
complexity to the polled wait which I introduced in an RFC patch.

09:57 < ickle_> it's only there as a fudge for waiting after irqs
after uninstalled during s&r, we aren't actually meant to hit it
09:57 < ickle_> so maybe we should just kill the code there and fix the breakage

v2: return -ENODEV instead of -EBUSY when irq_get fails

Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
---
 drivers/gpu/drm/i915/i915_gem.c |   25 +++++++++++--------------
 1 file changed, 11 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index c29c758..c5f0b03 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1864,22 +1864,19 @@ i915_wait_request(struct intel_ring_buffer *ring,
 	if (!i915_seqno_passed(ring->get_seqno(ring), seqno)) {
 		trace_i915_gem_request_wait_begin(ring, seqno);
 
-		if (ring->irq_get(ring)) {
-			if (dev_priv->mm.interruptible)
-				ret = wait_event_interruptible(ring->irq_queue,
-							       i915_seqno_passed(ring->get_seqno(ring), seqno)
-							       || atomic_read(&dev_priv->mm.wedged));
-			else
-				wait_event(ring->irq_queue,
-					   i915_seqno_passed(ring->get_seqno(ring), seqno)
-					   || atomic_read(&dev_priv->mm.wedged));
+		if (WARN_ON(!ring->irq_get(ring)))
+			return -ENODEV;
 
-			ring->irq_put(ring);
-		} else if (wait_for_atomic(i915_seqno_passed(ring->get_seqno(ring),
-							     seqno) ||
-					   atomic_read(&dev_priv->mm.wedged), 3000))
-			ret = -EBUSY;
+		if (dev_priv->mm.interruptible)
+			ret = wait_event_interruptible(ring->irq_queue,
+						       i915_seqno_passed(ring->get_seqno(ring), seqno)
+						       || atomic_read(&dev_priv->mm.wedged));
+		else
+			wait_event(ring->irq_queue,
+				   i915_seqno_passed(ring->get_seqno(ring), seqno)
+				   || atomic_read(&dev_priv->mm.wedged));
 
+		ring->irq_put(ring);
 		trace_i915_gem_request_wait_end(ring, seqno);
 	}
 	if (atomic_read(&dev_priv->mm.wedged))
-- 
1.7.10