drm/i915: Keep vblank interrupts enabled while enabling/disabling planes

Because of the upcoming vblank interrupt driven watermark update
mechanism we will have use for vblank interrupts during plane
enabling/disabling. So don't call drm_vblank_off() until planes
are off, and call drm_vblank_on() just before we start to enable
the planes.

v2: Pimp commit message (Paulo)
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -3883,6 +3883,8 @@ static void intel_crtc_enable_planes(struct drm_crtc *crtc)
 	int pipe = intel_crtc->pipe;
 	int plane = intel_crtc->plane;
 
+	drm_vblank_on(dev, pipe);
+
 	intel_enable_primary_hw_plane(dev_priv, plane, pipe);
 	intel_enable_planes(crtc);
 	/* The fixup needs to happen before cursor is enabled */
@@ -3908,7 +3910,6 @@ static void intel_crtc_disable_planes(struct drm_crtc *crtc)
 	int plane = intel_crtc->plane;
 
 	intel_crtc_wait_for_pending_flips(crtc);
-	drm_crtc_vblank_off(crtc);
 
 	if (dev_priv->fbc.plane == plane)
 		intel_disable_fbc(dev);
@@ -3919,6 +3920,8 @@ static void intel_crtc_disable_planes(struct drm_crtc *crtc)
 	intel_crtc_update_cursor(crtc, false);
 	intel_disable_planes(crtc);
 	intel_disable_primary_hw_plane(dev_priv, plane, pipe);
+
+	drm_vblank_off(dev, pipe);
 }
 
 static void ironlake_crtc_enable(struct drm_crtc *crtc)
@@ -3997,8 +4000,6 @@ static void ironlake_crtc_enable(struct drm_crtc *crtc)
 		cpt_verify_modeset(dev, intel_crtc->pipe);
 
 	intel_crtc_enable_planes(crtc);
-
-	drm_crtc_vblank_on(crtc);
 }
 
 /* IPS only exists on ULT machines and is tied to pipe A. */
@@ -4112,8 +4113,6 @@ static void haswell_crtc_enable(struct drm_crtc *crtc)
 	 * to change the workaround. */
 	haswell_mode_set_planes_workaround(intel_crtc);
 	intel_crtc_enable_planes(crtc);
-
-	drm_crtc_vblank_on(crtc);
 }
 
 static void ironlake_pfit_disable(struct intel_crtc *crtc)
@@ -4623,8 +4622,6 @@ static void valleyview_crtc_enable(struct drm_crtc *crtc)
 
 	intel_crtc_enable_planes(crtc);
 
-	drm_crtc_vblank_on(crtc);
-
 	/* Underruns don't raise interrupts, so check manually. */
 	i9xx_check_fifo_underruns(dev);
 }
@@ -4717,8 +4714,6 @@ static void i9xx_crtc_enable(struct drm_crtc *crtc)
 	if (IS_GEN2(dev))
 		intel_set_cpu_fifo_underrun_reporting(dev, pipe, true);
 
-	drm_crtc_vblank_on(crtc);
-
 	/* Underruns don't raise interrupts, so check manually. */
 	i9xx_check_fifo_underruns(dev);
 }