drm/i915: implement fastpath for overlay flip waiting

As long as the gpu can keep up, neither the cpu (waiting for gpu)
nore the gpu (waiting for vblank to do an overlay flip) stalls.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Eric Anholt <eric@anholt.net>

1 files changed, 34 insertions, 9 deletions

diff --git a/drivers/gpu/drm/i915/intel_overlay.c b/drivers/gpu/drm/i915/intel_overlay.c
index 4e88abb423b0..85e07e4459ce 100644
--- a/drivers/gpu/drm/i915/intel_overlay.c
+++ b/drivers/gpu/drm/i915/intel_overlay.c
@@ -251,7 +251,6 @@ static void intel_overlay_continue(struct intel_overlay *overlay,
         drm_i915_private_t *dev_priv = dev->dev_private;
         u32 flip_addr = overlay->flip_addr;
         u32 tmp;
-        int ret;
         RING_LOCALS;
 
         BUG_ON(!overlay->active);
@@ -264,11 +263,40 @@ static void intel_overlay_continue(struct intel_overlay *overlay,
         if (tmp & (1 << 17))
                 DRM_DEBUG("overlay underrun, DOVSTA: %x\n", tmp);
 
-        BEGIN_LP_RING(6);
+        BEGIN_LP_RING(4);
         OUT_RING(MI_FLUSH);
         OUT_RING(MI_NOOP);
         OUT_RING(MI_OVERLAY_FLIP | MI_OVERLAY_CONTINUE);
         OUT_RING(flip_addr);
+        ADVANCE_LP_RING();
+
+        overlay->last_flip_req = i915_add_request(dev, NULL, 0);
+}
+
+static int intel_overlay_wait_flip(struct intel_overlay *overlay)
+{
+        struct drm_device *dev = overlay->dev;
+        drm_i915_private_t *dev_priv = dev->dev_private;
+        int ret;
+        u32 tmp;
+        RING_LOCALS;
+
+        if (overlay->last_flip_req != 0) {
+                ret = i915_do_wait_request(dev, overlay->last_flip_req, 0);
+
+                if (ret != 0)
+                        return ret;
+
+                overlay->last_flip_req = 0;
+
+                tmp = I915_READ(ISR);
+
+                if (!(tmp & I915_OVERLAY_PLANE_FLIP_PENDING_INTERRUPT))
+                        return 0;
+        }
+
+        /* synchronous slowpath */
+        BEGIN_LP_RING(2);
         OUT_RING(MI_WAIT_FOR_EVENT | MI_WAIT_FOR_OVERLAY_FLIP);
         OUT_RING(MI_NOOP);
         ADVANCE_LP_RING();
@@ -279,13 +307,8 @@ static void intel_overlay_continue(struct intel_overlay *overlay,
                 DRM_ERROR("intel overlay: ring sync failed, hw likely wedged\n");
                 overlay->hw_wedged = 1;
         }
-}
 
-static int intel_overlay_wait_flip(struct intel_overlay *overlay)
-{
-        /* don't overcomplicate things for now with asynchronous operations
-         * see comment above */
-        return 0;
+        return ret;
 }
 
 /* overlay needs to be disabled in OCMD reg */
@@ -344,7 +367,9 @@ static int intel_overlay_off(struct intel_overlay *overlay)
         return ret;
 }
 
-/* wait for pending overlay flip and release old frame */
+/* Wait for pending overlay flip and release old frame.
+ * Needs to be called before the overlay register are changed
+ * via intel_overlay_(un)map_regs_atomic */
 static int intel_overlay_release_old_vid(struct intel_overlay *overlay)
 {
         int ret;