drm/i915: Add support for detecting vblanks when hw frame counter is unavailable.

This uses the newly created drm_accurate_vblank_count_and_time to accurately
get a vblank count when the hw counter is unavailable.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1463490484-19540-6-git-send-email-maarten.lankhorst@linux.intel.com
Reviewed-by: Patrik Jakobsson <patrik.jakobsson@linux.intel.com>

drivers/gpu/drm/i915/intel_display.c

@@ -13413,6 +13413,16 @@ static int intel_atomic_prepare_commit(struct drm_device *dev,
 	return ret;
 }
 
+u32 intel_crtc_get_vblank_counter(struct intel_crtc *crtc)
+{
+	struct drm_device *dev = crtc->base.dev;
+
+	if (!dev->max_vblank_count)
+		return drm_accurate_vblank_count(&crtc->base);
+
+	return dev->driver->get_vblank_counter(dev, crtc->pipe);
+}
+
 static void intel_atomic_wait_for_vblanks(struct drm_device *dev,
 					  struct drm_i915_private *dev_priv,
 					  unsigned crtc_mask)

drivers/gpu/drm/i915/intel_drv.h

@@ -1178,6 +1178,9 @@ intel_wait_for_vblank_if_active(struct drm_device *dev, int pipe)
 	if (crtc->active)
 		intel_wait_for_vblank(dev, pipe);
 }
+
+u32 intel_crtc_get_vblank_counter(struct intel_crtc *crtc);
+
 int ironlake_get_lanes_required(int target_clock, int link_bw, int bpp);
 void vlv_wait_port_ready(struct drm_i915_private *dev_priv,
 			 struct intel_digital_port *dport,

drivers/gpu/drm/i915/intel_sprite.c

@@ -80,9 +80,7 @@ static int usecs_to_scanlines(const struct drm_display_mode *adjusted_mode,
  */
 void intel_pipe_update_start(struct intel_crtc *crtc)
 {
-	struct drm_device *dev = crtc->base.dev;
 	const struct drm_display_mode *adjusted_mode = &crtc->config->base.adjusted_mode;
-	enum pipe pipe = crtc->pipe;
 	long timeout = msecs_to_jiffies_timeout(1);
 	int scanline, min, max, vblank_start;
 	wait_queue_head_t *wq = drm_crtc_vblank_waitqueue(&crtc->base);
@@ -139,8 +137,7 @@ void intel_pipe_update_start(struct intel_crtc *crtc)
 
 	crtc->debug.scanline_start = scanline;
 	crtc->debug.start_vbl_time = ktime_get();
-	crtc->debug.start_vbl_count =
-		dev->driver->get_vblank_counter(dev, pipe);
+	crtc->debug.start_vbl_count = intel_crtc_get_vblank_counter(crtc);
 
 	trace_i915_pipe_update_vblank_evaded(crtc);
 }
@@ -156,10 +153,9 @@ void intel_pipe_update_start(struct intel_crtc *crtc)
  */
 void intel_pipe_update_end(struct intel_crtc *crtc)
 {
-	struct drm_device *dev = crtc->base.dev;
 	enum pipe pipe = crtc->pipe;
 	int scanline_end = intel_get_crtc_scanline(crtc);
-	u32 end_vbl_count = dev->driver->get_vblank_counter(dev, pipe);
+	u32 end_vbl_count = intel_crtc_get_vblank_counter(crtc);
 	ktime_t end_vbl_time = ktime_get();
 
 	trace_i915_pipe_update_end(crtc, end_vbl_count, scanline_end);