drm/i915: Reset power sequencer pipe tracking when disp2d is off

The power sequencer loses its state when the disp2d power well is down.
Clear the dev_priv->pps_pipe tracking so that the power sequencer state
gets reinitialized the next time it's needed.

v2: Fix the pps_mutex vs. power_domain mutex deadlock by taking power
    domain reference first
v3: Rename from edp_pps_(un)lock() to just pps_(un)lock() for the future,
    update due to backlight code changes
Reviewed-by: Imre Deak <imre.deak@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_drv.h

@@ -946,6 +946,7 @@ void intel_dp_mst_suspend(struct drm_device *dev);
 void intel_dp_mst_resume(struct drm_device *dev);
 int intel_dp_max_link_bw(struct intel_dp *intel_dp);
 void intel_dp_hot_plug(struct intel_encoder *intel_encoder);
+void vlv_power_sequencer_reset(struct drm_i915_private *dev_priv);
 /* intel_dp_mst.c */
 int intel_dp_mst_encoder_init(struct intel_digital_port *intel_dig_port, int conn_id);
 void intel_dp_mst_encoder_cleanup(struct intel_digital_port *intel_dig_port);

drivers/gpu/drm/i915/intel_pm.c

@@ -6468,6 +6468,8 @@ static void vlv_display_power_well_disable(struct drm_i915_private *dev_priv,
 	spin_unlock_irq(&dev_priv->irq_lock);
 
 	vlv_set_power_well(dev_priv, power_well, false);
+
+	vlv_power_sequencer_reset(dev_priv);
 }
 
 static void vlv_dpio_cmn_power_well_enable(struct drm_i915_private *dev_priv,