i915_vblank_tasklet: Try harder to avoid tearing.

Previously, if there were several buffer swaps scheduled for the same vertical
blank, all but the first blit emitted stood a chance of exhibiting tearing. In
order to avoid this, split the blits along slices of each output top to bottom.

Signed-off-by: Dave Airlie <airlied@linux.ie>

diff --git a/drivers/char/drm/i915_irq.c b/drivers/char/drm/i915_irq.c
index e5463b111fc094a173ce4ddf73b89c70f7974ce5..e2c4b3a41b1e33bb64d7c379c21e4873de9fcbf0 100644 (file)
--- a/drivers/char/drm/i915_irq.c
+++ b/drivers/char/drm/i915_irq.c
@@ -46,88 +46,167 @@ static void i915_vblank_tasklet(drm_device_t *dev)
 {
        drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
        unsigned long irqflags;
-       struct list_head *list, *tmp;
+       struct list_head *list, *tmp, hits, *hit;
+       int nhits, nrects, slice[2], upper[2], lower[2], i;
+       unsigned counter[2] = { atomic_read(&dev->vbl_received),
+                               atomic_read(&dev->vbl_received2) };
+       drm_drawable_info_t *drw;
+       drm_i915_sarea_t *sarea_priv = dev_priv->sarea_priv;
+       u32 cpp = dev_priv->cpp;
+       u32 cmd = (cpp == 4) ? (XY_SRC_COPY_BLT_CMD |
+                               XY_SRC_COPY_BLT_WRITE_ALPHA |
+                               XY_SRC_COPY_BLT_WRITE_RGB)
+                            : XY_SRC_COPY_BLT_CMD;
+       u32 pitchropcpp = (sarea_priv->pitch * cpp) | (0xcc << 16) |
+                         (cpp << 23) | (1 << 24);
+       RING_LOCALS;
 
        DRM_DEBUG("\n");
 
+       INIT_LIST_HEAD(&hits);
+
+       nhits = nrects = 0;
+
        spin_lock_irqsave(&dev_priv->swaps_lock, irqflags);
 
+       /* Find buffer swaps scheduled for this vertical blank */
        list_for_each_safe(list, tmp, &dev_priv->vbl_swaps.head) {
                drm_i915_vbl_swap_t *vbl_swap =
                        list_entry(list, drm_i915_vbl_swap_t, head);
-               atomic_t *counter = vbl_swap->pipe ? &dev->vbl_received2 :
-                       &dev->vbl_received;
-
-               if ((atomic_read(counter) - vbl_swap->sequence) <= (1<<23)) {
-                       drm_drawable_info_t *drw;
-
-                       spin_unlock(&dev_priv->swaps_lock);
-
-                       spin_lock(&dev->drw_lock);
-
-                       drw = drm_get_drawable_info(dev, vbl_swap->drw_id);
-                               
-                       if (drw) {
-                               int i, num_rects = drw->num_rects;
-                               drm_clip_rect_t *rect = drw->rects;
-                               drm_i915_sarea_t *sarea_priv =
-                                   dev_priv->sarea_priv;
-                               u32 cpp = dev_priv->cpp;
-                               u32 cmd = (cpp == 4) ? (XY_SRC_COPY_BLT_CMD |
-                                                       XY_SRC_COPY_BLT_WRITE_ALPHA |
-                                                       XY_SRC_COPY_BLT_WRITE_RGB)
-                                                    : XY_SRC_COPY_BLT_CMD;
-                               u32 pitchropcpp = (sarea_priv->pitch * cpp) |
-                                                 (0xcc << 16) | (cpp << 23) |
-                                                 (1 << 24);
-                               RING_LOCALS;
-
-                               i915_kernel_lost_context(dev);
-
-                               BEGIN_LP_RING(6);
-
-                               OUT_RING(GFX_OP_DRAWRECT_INFO);
-                               OUT_RING(0);
-                               OUT_RING(0);
-                               OUT_RING(sarea_priv->width |
-                                        sarea_priv->height << 16);
-                               OUT_RING(sarea_priv->width |
-                                        sarea_priv->height << 16);
-                               OUT_RING(0);
 
-                               ADVANCE_LP_RING();
+               if ((counter[vbl_swap->pipe] - vbl_swap->sequence) > (1<<23))
+                       continue;
+
+               list_del(list);
+               dev_priv->swaps_pending--;
 
-                               sarea_priv->ctxOwner = DRM_KERNEL_CONTEXT;
+               spin_unlock(&dev_priv->swaps_lock);
+               spin_lock(&dev->drw_lock);
 
-                               for (i = 0; i < num_rects; i++, rect++) {
-                                       BEGIN_LP_RING(8);
+               drw = drm_get_drawable_info(dev, vbl_swap->drw_id);
+
+               if (!drw) {
+                       spin_unlock(&dev->drw_lock);
+                       drm_free(vbl_swap, sizeof(*vbl_swap), DRM_MEM_DRIVER);
+                       spin_lock(&dev_priv->swaps_lock);
+                       continue;
+               }
 
-                                       OUT_RING(cmd);
-                                       OUT_RING(pitchropcpp);
-                                       OUT_RING((rect->y1 << 16) | rect->x1);
-                                       OUT_RING((rect->y2 << 16) | rect->x2);
-                                       OUT_RING(sarea_priv->front_offset);
-                                       OUT_RING((rect->y1 << 16) | rect->x1);
-                                       OUT_RING(pitchropcpp & 0xffff);
-                                       OUT_RING(sarea_priv->back_offset);
+               list_for_each(hit, &hits) {
+                       drm_i915_vbl_swap_t *swap_cmp =
+                               list_entry(hit, drm_i915_vbl_swap_t, head);
+                       drm_drawable_info_t *drw_cmp =
+                               drm_get_drawable_info(dev, swap_cmp->drw_id);
 
-                                       ADVANCE_LP_RING();
-                               }
+                       if (drw_cmp &&
+                           drw_cmp->rects[0].y1 > drw->rects[0].y1) {
+                               list_add_tail(list, hit);
+                               break;
                        }
+               }
 
-                       spin_unlock(&dev->drw_lock);
+               spin_unlock(&dev->drw_lock);
 
-                       spin_lock(&dev_priv->swaps_lock);
+               /* List of hits was empty, or we reached the end of it */
+               if (hit == &hits)
+                       list_add_tail(list, hits.prev);
 
-                       list_del(list);
+               nhits++;
 
-                       drm_free(vbl_swap, sizeof(*vbl_swap), DRM_MEM_DRIVER);
+               spin_lock(&dev_priv->swaps_lock);
+       }
+
+       if (nhits == 0) {
+               spin_unlock_irqrestore(&dev_priv->swaps_lock, irqflags);
+               return;
+       }
+
+       spin_unlock(&dev_priv->swaps_lock);
 
-                       dev_priv->swaps_pending--;
+       i915_kernel_lost_context(dev);
+
+       BEGIN_LP_RING(6);
+
+       OUT_RING(GFX_OP_DRAWRECT_INFO);
+       OUT_RING(0);
+       OUT_RING(0);
+       OUT_RING(sarea_priv->width | sarea_priv->height << 16);
+       OUT_RING(sarea_priv->width | sarea_priv->height << 16);
+       OUT_RING(0);
+
+       ADVANCE_LP_RING();
+
+       sarea_priv->ctxOwner = DRM_KERNEL_CONTEXT;
+
+       upper[0] = upper[1] = 0;
+       slice[0] = max(sarea_priv->pipeA_h / nhits, 1);
+       slice[1] = max(sarea_priv->pipeB_h / nhits, 1);
+       lower[0] = sarea_priv->pipeA_y + slice[0];
+       lower[1] = sarea_priv->pipeB_y + slice[0];
+
+       spin_lock(&dev->drw_lock);
+
+       /* Emit blits for buffer swaps, partitioning both outputs into as many
+        * slices as there are buffer swaps scheduled in order to avoid tearing
+        * (based on the assumption that a single buffer swap would always
+        * complete before scanout starts).
+        */
+       for (i = 0; i++ < nhits;
+            upper[0] = lower[0], lower[0] += slice[0],
+            upper[1] = lower[1], lower[1] += slice[1]) {
+               if (i == nhits)
+                       lower[0] = lower[1] = sarea_priv->height;
+
+               list_for_each(hit, &hits) {
+                       drm_i915_vbl_swap_t *swap_hit =
+                               list_entry(hit, drm_i915_vbl_swap_t, head);
+                       drm_clip_rect_t *rect;
+                       int num_rects, pipe;
+                       unsigned short top, bottom;
+
+                       drw = drm_get_drawable_info(dev, swap_hit->drw_id);
+
+                       if (!drw)
+                               continue;
+
+                       rect = drw->rects;
+                       pipe = swap_hit->pipe;
+                       top = upper[pipe];
+                       bottom = lower[pipe];
+
+                       for (num_rects = drw->num_rects; num_rects--; rect++) {
+                               int y1 = max(rect->y1, top);
+                               int y2 = min(rect->y2, bottom);
+
+                               if (y1 >= y2)
+                                       continue;
+
+                               BEGIN_LP_RING(8);
+
+                               OUT_RING(cmd);
+                               OUT_RING(pitchropcpp);
+                               OUT_RING((y1 << 16) | rect->x1);
+                               OUT_RING((y2 << 16) | rect->x2);
+                               OUT_RING(sarea_priv->front_offset);
+                               OUT_RING((y1 << 16) | rect->x1);
+                               OUT_RING(pitchropcpp & 0xffff);
+                               OUT_RING(sarea_priv->back_offset);
+
+                               ADVANCE_LP_RING();
+                       }
                }
        }
 
-       spin_unlock_irqrestore(&dev_priv->swaps_lock, irqflags);
+       spin_unlock_irqrestore(&dev->drw_lock, irqflags);
+
+       list_for_each_safe(hit, tmp, &hits) {
+               drm_i915_vbl_swap_t *swap_hit =
+                       list_entry(hit, drm_i915_vbl_swap_t, head);
+
+               list_del(hit);
+
+               drm_free(swap_hit, sizeof(*swap_hit), DRM_MEM_DRIVER);
+       }
 }
 
 irqreturn_t i915_driver_irq_handler(DRM_IRQ_ARGS)