drm/tegra: dc: Implement hardware VBLANK counter

The display controller on Tegra can use syncpoints to count VBLANK
events. syncpoints are 32-bit unsigned integers, so well suited as
VBLANK counters.

Signed-off-by: Thierry Reding <treding@nvidia.com>
diff --git a/drivers/gpu/drm/tegra/drm.h b/drivers/gpu/drm/tegra/drm.h
index 8cb2dfe..ded04e3 100644
--- a/drivers/gpu/drm/tegra/drm.h
+++ b/drivers/gpu/drm/tegra/drm.h
@@ -106,6 +106,7 @@
 
 struct tegra_dc {
 	struct host1x_client client;
+	struct host1x_syncpt *syncpt;
 	struct device *dev;
 	spinlock_t lock;
 
@@ -180,6 +181,7 @@
 };
 
 /* from dc.c */
+u32 tegra_dc_get_vblank_counter(struct tegra_dc *dc);
 void tegra_dc_enable_vblank(struct tegra_dc *dc);
 void tegra_dc_disable_vblank(struct tegra_dc *dc);
 void tegra_dc_cancel_page_flip(struct drm_crtc *crtc, struct drm_file *file);