drm/i915: Wait upon the last request seqno, rather than a future seqno

In commit 69c2fc891343cb5217c866d10709343cff190bdc
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Fri Jul 20 12:41:03 2012 +0100

    drm/i915: Remove the per-ring write list

the explicit flush was removed from i915_ring_idle(). However, we
continued to wait upon the next seqno which now did not correspond to
any request (except for the unusual condition of a failure to queue a
request after execbuffer) and so would wait indefinitely.

This has an important side-effect that i915_gpu_idle() does not cause
the seqno to be incremented. This is vital if we are to be able to idle
the GPU to handle seqno wraparound, as in subsequent patches.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 21 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index b0016bb6563..9be450e7c54 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2462,10 +2462,29 @@ i915_gem_object_unbind(struct drm_i915_gem_object *obj)
 
 static int i915_ring_idle(struct intel_ring_buffer *ring)
 {
-        if (list_empty(&ring->active_list))
+        u32 seqno;
+        int ret;
+
+        /* We need to add any requests required to flush the objects */
+        if (!list_empty(&ring->active_list)) {
+                seqno = list_entry(ring->active_list.prev,
+                                   struct drm_i915_gem_object,
+                                   ring_list)->last_read_seqno;
+
+                ret = i915_gem_check_olr(ring, seqno);
+                if (ret)
+                        return ret;
+        }
+
+        /* Wait upon the last request to be completed */
+        if (list_empty(&ring->request_list))
                 return 0;
 
-        return i915_wait_seqno(ring, i915_gem_next_request_seqno(ring));
+        seqno = list_entry(ring->request_list.prev,
+                           struct drm_i915_gem_request,
+                           list)->seqno;
+
+        return i915_wait_seqno(ring, seqno);
 }
 
 int i915_gpu_idle(struct drm_device *dev)