[PATCH 2/5] drm/vblank: Restoring vblank counts after device runtime PM events.

[Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>]

The HW frame counter can get reset when devices enters low power
states and this messes up any following vblank count updates. So, compute
the missed vblank interrupts for that low power state duration using time
stamps. This is similar to _crtc_vblank_on() except that it doesn't enable
vblank interrupts because this function is expected to be called from
the driver _enable_vblank() vfunc.

Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
---
 drivers/gpu/drm/drm_vblank.c | 30 ++++++++++++++++++++++++++++++
 include/drm/drm_vblank.h     |  1 +
 2 files changed, 31 insertions(+)

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index 7eee82c06ed8..69d537cea149 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -1230,6 +1230,36 @@ void drm_crtc_vblank_on(struct drm_crtc *crtc)
 }
 EXPORT_SYMBOL(drm_crtc_vblank_on);
 
+void drm_crtc_vblank_restore(struct drm_device *dev, unsigned int pipe)
+{
+	ktime_t t_vblank;
+	struct drm_vblank_crtc *vblank;
+	int framedur_ns;
+	u64 diff_ns;
+	u32 cur_vblank, diff = 1;
+	int count = DRM_TIMESTAMP_MAXRETRIES;
+
+	if (WARN_ON(pipe >= dev->num_crtcs))
+		return;
+
+	vblank = &dev->vblank[pipe];
+	framedur_ns = vblank->framedur_ns;
+
+	do {
+		cur_vblank = __get_vblank_counter(dev, pipe);
+		drm_get_last_vbltimestamp(dev, pipe, &t_vblank, false);
+	} while (cur_vblank != __get_vblank_counter(dev, pipe) && --count > 0);
+
+	diff_ns = ktime_to_ns(ktime_sub(t_vblank, vblank->time));
+	if (framedur_ns)
+		diff = DIV_ROUND_CLOSEST_ULL(diff_ns, framedur_ns);
+
+	DRM_DEBUG_VBL("computing missed vblanks %lld/%d=%d after HW counter reset hw_diff=%d\n",
+		      diff_ns, framedur_ns, diff, cur_vblank - vblank->last);
+	store_vblank(dev, pipe, diff, t_vblank, cur_vblank);
+}
+EXPORT_SYMBOL(drm_crtc_vblank_restore);
+
 static void drm_legacy_vblank_pre_modeset(struct drm_device *dev,
 					  unsigned int pipe)
 {
diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h
index 848b463a0af5..aafcbef91bd7 100644
--- a/include/drm/drm_vblank.h
+++ b/include/drm/drm_vblank.h
@@ -180,6 +180,7 @@ void drm_crtc_vblank_off(struct drm_crtc *crtc);
 void drm_crtc_vblank_reset(struct drm_crtc *crtc);
 void drm_crtc_vblank_on(struct drm_crtc *crtc);
 u32 drm_crtc_accurate_vblank_count(struct drm_crtc *crtc);
+void drm_crtc_vblank_restore(struct drm_device *dev, unsigned int pipe);
 
 bool drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev,
 					   unsigned int pipe, int *max_error,
-- 
2.11.0

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel