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>

5 files changed, 119 insertions, 6 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index bdb29b2a01ed..9eee6cf7901e 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/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,
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 30780f2cab6f..53dfc8398a96 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/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);
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index e4a2e2c3dbe3..adf983f01dda 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/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.
  */
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 820e9dfaadc7..c2231f7d2d97 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/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)
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)