[PATCH 08/10] drm/i915: real wait seqno with timeout

[Ben Widawsky <ben@bwidawsk.net>]

Move the final interesting chunk from i915_wait_seqno into a timed
variant. The timed variant can take a NULL or 0 timeout argument to
preserve the old behavior, and this allowing the old (still useful
function) to call directly into the timed variant.

This code does not require struct_mutex, therefore it can wait on events
without holding the lock.

Signed-off-by: Ben Widawsky <benjamin.widawsky@intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c |   53 ++++++++++++++++++++++++++-------------
 1 file changed, 36 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 7bfad04..e446d9c 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1879,6 +1879,40 @@ static int __wait_seqno(struct intel_ring_buffer *ring, u32 seqno,
 	}
 }
 
+static int
+i915_seqno_wait_timed(struct intel_ring_buffer *ring, u32 seqno,
+		      bool interruptible, long *timeout)
+{
+	bool wait_forever = false;
+	int ret = 0;
+
+	BUG_ON(seqno == ring->outstanding_lazy_request);
+
+	if (timeout == NULL || ((*timeout) < 0))
+		wait_forever = true;
+
+	if (!i915_seqno_passed(ring->get_seqno(ring), seqno)) {
+		trace_i915_gem_request_wait_begin(ring, seqno);
+
+		if (WARN_ON(!ring->irq_get(ring)))
+			return -EBUSY;
+
+		do {
+			long time = wait_forever ? SEQNO_WAIT_DEFAULT : *timeout;
+			ret  = __wait_seqno(ring, seqno,
+					    interruptible,
+					    &time);
+			if (ret == 0 && timeout)
+				*timeout = time;
+		} while (ret == -ETIME && wait_forever);
+
+		ring->irq_put(ring);
+		trace_i915_gem_request_wait_end(ring, seqno);
+	}
+
+	return ret;
+}
+
 /**
  * Waits for a sequence number to be signaled, and cleans up the
  * request and object lists appropriately for that event.
@@ -1920,23 +1954,8 @@ i915_wait_request(struct intel_ring_buffer *ring,
 
 		seqno = request->seqno;
 	}
-
-	if (!i915_seqno_passed(ring->get_seqno(ring), seqno)) {
-		trace_i915_gem_request_wait_begin(ring, seqno);
-
-		if (WARN_ON(!ring->irq_get(ring)))
-			return -EBUSY;
-
-		do {
-			long time = SEQNO_WAIT_DEFAULT;
-			ret  = __wait_seqno(ring, seqno,
-					    dev_priv->mm.interruptible,
-					    &time);
-		} while (ret == -ETIME);
-
-		ring->irq_put(ring);
-		trace_i915_gem_request_wait_end(ring, seqno);
-	}
+	ret = i915_seqno_wait_timed(ring, seqno, dev_priv->mm.interruptible,
+				    NULL);
 	if (atomic_read(&dev_priv->mm.wedged))
 		ret = -EAGAIN;
 
-- 
1.7.10