drm/i915: Add support for precise vblank timestamping (v2)

v2: Change IS_IRONLAKE to IS_GEN5 to adapt to 2.6.37

This patch adds new functions for use by the drm core:

.get_vblank_timestamp() provides a precise timestamp
for the end of the most recent (or current) vblank
interval of a given crtc, as needed for the DRI2
implementation of the OML_sync_control extension.
It is a thin wrapper around the drm function
drm_calc_vbltimestamp_from_scanoutpos() which does
almost all the work.

.get_scanout_position() provides the current horizontal
and vertical video scanout position and "in vblank"
status of a given crtc, as needed by the drm for use by
drm_calc_vbltimestamp_from_scanoutpos().

The patch modifies the pageflip completion routine
to use these precise vblank timestamps as the timestamps
for pageflip completion events.

This code has been only tested on a HP-Mini Netbook with
Atom processor and Intel 945GME gpu. The codepath for
(IS_G4X(dev) || IS_GEN5(dev) || IS_GEN6(dev)) gpu's
has not been tested so far due to lack of hardware.

Signed-off-by: Mario Kleiner <mario.kleiner@tuebingen.mpg.de>
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 23 insertions, 6 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 8645a974a499..0c201d684584 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -5252,7 +5252,8 @@ static void intel_unpin_work_fn(struct work_struct *__work)
 }
 
 static void do_intel_finish_page_flip(struct drm_device *dev,
-                                      struct drm_crtc *crtc)
+                                      struct drm_crtc *crtc,
+                                      int called_before_vblirq)
 {
         drm_i915_private_t *dev_priv = dev->dev_private;
         struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
@@ -5274,19 +5275,33 @@ static void do_intel_finish_page_flip(struct drm_device *dev,
         }
 
         intel_crtc->unpin_work = NULL;
-        drm_vblank_put(dev, intel_crtc->pipe);
 
         if (work->event) {
                 e = work->event;
-                do_gettimeofday(&now);
-                e->event.sequence = drm_vblank_count(dev, intel_crtc->pipe);
+                e->event.sequence = drm_vblank_count_and_time(dev, intel_crtc->pipe, &now);
+
+                /* Called before vblank count and timestamps have
+                 * been updated for the vblank interval of flip
+                 * completion? Need to increment vblank count and
+                 * add one videorefresh duration to returned timestamp
+                 * to account for this.
+                 */
+                if (called_before_vblirq) {
+                        e->event.sequence++;
+                        now = ns_to_timeval(timeval_to_ns(&now) +
+                                            crtc->framedur_ns);
+                }
+
                 e->event.tv_sec = now.tv_sec;
                 e->event.tv_usec = now.tv_usec;
+
                 list_add_tail(&e->base.link,
                               &e->base.file_priv->event_list);
                 wake_up_interruptible(&e->base.file_priv->event_wait);
         }
 
+        drm_vblank_put(dev, intel_crtc->pipe);
+
         spin_unlock_irqrestore(&dev->event_lock, flags);
 
         obj = work->old_fb_obj;
@@ -5306,7 +5321,8 @@ void intel_finish_page_flip(struct drm_device *dev, int pipe)
         drm_i915_private_t *dev_priv = dev->dev_private;
         struct drm_crtc *crtc = dev_priv->pipe_to_crtc_mapping[pipe];
 
-        do_intel_finish_page_flip(dev, crtc);
+        /* Called after drm_handle_vblank has run for finish vblank. */
+        do_intel_finish_page_flip(dev, crtc, 0);
 }
 
 void intel_finish_page_flip_plane(struct drm_device *dev, int plane)
@@ -5314,7 +5330,8 @@ void intel_finish_page_flip_plane(struct drm_device *dev, int plane)
         drm_i915_private_t *dev_priv = dev->dev_private;
         struct drm_crtc *crtc = dev_priv->plane_to_crtc_mapping[plane];
 
-        do_intel_finish_page_flip(dev, crtc);
+        /* Called before drm_handle_vblank has run for finish vblank. */
+        do_intel_finish_page_flip(dev, crtc, 1);
 }
 
 void intel_prepare_page_flip(struct drm_device *dev, int plane)