drm/i915: Add pipe update trace points

Add trace points for observing the atomic pipe update mechanism.

v2: Rebased due to earlier changes
v3: Pass intel_crtc instead of drm_crtc (Daniel)
v4: Pass frame counter from the caller to evaded/end since
    the caller now always has that ready

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Sourab Gupta <sourabgupta@gmail.com>
Reviewed-by: Akash Goel <akash.goels@gmail.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c
index 6192e58..213cd58 100644
--- a/drivers/gpu/drm/i915/intel_sprite.c
+++ b/drivers/gpu/drm/i915/intel_sprite.c
@@ -73,6 +73,8 @@
 
 	local_irq_disable();
 
+	trace_i915_pipe_update_start(crtc, min, max);
+
 	for (;;) {
 		/*
 		 * prepare_to_wait() has a memory barrier, which guarantees
@@ -104,6 +106,8 @@
 
 	*start_vbl_count = dev->driver->get_vblank_counter(dev, pipe);
 
+	trace_i915_pipe_update_vblank_evaded(crtc, min, max, *start_vbl_count);
+
 	return true;
 }
 
@@ -113,6 +117,8 @@
 	enum pipe pipe = crtc->pipe;
 	u32 end_vbl_count = dev->driver->get_vblank_counter(dev, pipe);
 
+	trace_i915_pipe_update_end(crtc, end_vbl_count);
+
 	local_irq_enable();
 
 	if (start_vbl_count != end_vbl_count)