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>

drivers/gpu/drm/i915/i915_drv.c

@@ -652,6 +652,8 @@ static struct drm_driver driver = {
 	.device_is_agp = i915_driver_device_is_agp,
 	.enable_vblank = i915_enable_vblank,
 	.disable_vblank = i915_disable_vblank,
+	.get_vblank_timestamp = i915_get_vblank_timestamp,
+	.get_scanout_position = i915_get_crtc_scanoutpos,
 	.irq_preinstall = i915_driver_irq_preinstall,
 	.irq_postinstall = i915_driver_irq_postinstall,
 	.irq_uninstall = i915_driver_irq_uninstall,

drivers/gpu/drm/i915/i915_drv.h

@@ -1019,6 +1019,13 @@ void
 i915_disable_pipestat(drm_i915_private_t *dev_priv, int pipe, u32 mask);
 
 void intel_enable_asle (struct drm_device *dev);
+int i915_get_vblank_timestamp(struct drm_device *dev, int crtc,
+			      int *max_error,
+			      struct timeval *vblank_time,
+			      unsigned flags);
+
+int i915_get_crtc_scanoutpos(struct drm_device *dev, int pipe,
+			     int *vpos, int *hpos);
 
 #ifdef CONFIG_DEBUG_FS
 extern void i915_destroy_error_state(struct drm_device *dev);

drivers/gpu/drm/i915/i915_irq.c

@@ -248,6 +248,92 @@ u32 gm45_get_vblank_counter(struct drm_device *dev, int pipe)
 	return I915_READ(reg);
 }
 
+int i915_get_crtc_scanoutpos(struct drm_device *dev, int pipe,
+			     int *vpos, int *hpos)
+{
+	drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
+	u32 vbl = 0, position = 0;
+	int vbl_start, vbl_end, htotal, vtotal;
+	bool in_vbl = true;
+	int ret = 0;
+
+	if (!i915_pipe_enabled(dev, pipe)) {
+		DRM_DEBUG_DRIVER("trying to get scanoutpos for disabled "
+					"pipe %d\n", pipe);
+		return 0;
+	}
+
+	/* Get vtotal. */
+	vtotal = 1 + ((I915_READ(VTOTAL(pipe)) >> 16) & 0x1fff);
+
+	if (INTEL_INFO(dev)->gen >= 4) {
+		/* No obvious pixelcount register. Only query vertical
+		 * scanout position from Display scan line register.
+		 */
+		position = I915_READ(PIPEDSL(pipe));
+
+		/* Decode into vertical scanout position. Don't have
+		 * horizontal scanout position.
+		 */
+		*vpos = position & 0x1fff;
+		*hpos = 0;
+	} else {
+		/* Have access to pixelcount since start of frame.
+		 * We can split this into vertical and horizontal
+		 * scanout position.
+		 */
+		position = (I915_READ(PIPEFRAMEPIXEL(pipe)) & PIPE_PIXEL_MASK) >> PIPE_PIXEL_SHIFT;
+
+		htotal = 1 + ((I915_READ(HTOTAL(pipe)) >> 16) & 0x1fff);
+		*vpos = position / htotal;
+		*hpos = position - (*vpos * htotal);
+	}
+
+	/* Query vblank area. */
+	vbl = I915_READ(VBLANK(pipe));
+
+	/* Test position against vblank region. */
+	vbl_start = vbl & 0x1fff;
+	vbl_end = (vbl >> 16) & 0x1fff;
+
+	if ((*vpos < vbl_start) || (*vpos > vbl_end))
+		in_vbl = false;
+
+	/* Inside "upper part" of vblank area? Apply corrective offset: */
+	if (in_vbl && (*vpos >= vbl_start))
+		*vpos = *vpos - vtotal;
+
+	/* Readouts valid? */
+	if (vbl > 0)
+		ret |= DRM_SCANOUTPOS_VALID | DRM_SCANOUTPOS_ACCURATE;
+
+	/* In vblank? */
+	if (in_vbl)
+		ret |= DRM_SCANOUTPOS_INVBL;
+
+	return ret;
+}
+
+int i915_get_vblank_timestamp(struct drm_device *dev, int crtc,
+			      int *max_error,
+			      struct timeval *vblank_time,
+			      unsigned flags)
+{
+	struct drm_crtc *drmcrtc;
+
+	if (crtc < 0 || crtc >= dev->num_crtcs) {
+		DRM_ERROR("Invalid crtc %d\n", crtc);
+		return -EINVAL;
+	}
+
+	/* Get drm_crtc to timestamp: */
+	drmcrtc = intel_get_crtc_for_pipe(dev, crtc);
+
+	/* Helper routine in DRM core does all the work: */
+	return drm_calc_vbltimestamp_from_scanoutpos(dev, crtc, max_error,
+						     vblank_time, flags, drmcrtc);
+}
+
 /*
  * Handle hotplug events outside the interrupt handler proper.
  */

drivers/gpu/drm/i915/i915_reg.h

@@ -2253,6 +2253,7 @@
 #define PIPESRC(pipe) _PIPE(pipe, PIPEASRC, PIPEBSRC)
 #define PIPECONF(pipe) _PIPE(pipe, PIPEACONF, PIPEBCONF)
 #define PIPEDSL(pipe)  _PIPE(pipe, PIPEADSL, PIPEBDSL)
+#define PIPEFRAMEPIXEL(pipe)  _PIPE(pipe, PIPEAFRAMEPIXEL, PIPEBFRAMEPIXEL)
 
 #define DSPARB			0x70030
 #define   DSPARB_CSTART_MASK	(0x7f << 7)

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)