drm/i915: Do intel_panel_destroy_backlight() later

Currently we destroy the backlight during connector unregistration.
That means the final modeset performed by drm_atomic_helper_shutdown()
will leave the backlight on. We don't want that so let's just move
intel_panel_destroy_backlight() into intel_panel_fini() which gets
called during connector destuction.

We still unregister the user visible backlight device during connector
unregistration.

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181008134641.24868-1-ville.syrjala@linux.intel.comReviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106386

drivers/gpu/drm/i915/intel_display.c

@@ -15860,7 +15860,6 @@ void intel_connector_unregister(struct drm_connector *connector)
 	struct intel_connector *intel_connector = to_intel_connector(connector);
 
 	intel_backlight_device_unregister(intel_connector);
-	intel_panel_destroy_backlight(connector);
 }
 
 static void intel_hpd_poll_fini(struct drm_device *dev)

drivers/gpu/drm/i915/intel_drv.h

@@ -1904,7 +1904,6 @@ int intel_panel_setup_backlight(struct drm_connector *connector,
 void intel_panel_enable_backlight(const struct intel_crtc_state *crtc_state,
 				  const struct drm_connector_state *conn_state);
 void intel_panel_disable_backlight(const struct drm_connector_state *old_conn_state);
-void intel_panel_destroy_backlight(struct drm_connector *connector);
 extern struct drm_display_mode *intel_find_panel_downclock(
 				struct drm_i915_private *dev_priv,
 				struct drm_display_mode *fixed_mode,

drivers/gpu/drm/i915/intel_panel.c

@@ -1814,11 +1814,8 @@ int intel_panel_setup_backlight(struct drm_connector *connector, enum pipe pipe)
 	return 0;
 }
 
-void intel_panel_destroy_backlight(struct drm_connector *connector)
+static void intel_panel_destroy_backlight(struct intel_panel *panel)
 {
-	struct intel_connector *intel_connector = to_intel_connector(connector);
-	struct intel_panel *panel = &intel_connector->panel;
-
 	/* dispose of the pwm */
 	if (panel->backlight.pwm)
 		pwm_put(panel->backlight.pwm);
@@ -1923,6 +1920,8 @@ void intel_panel_fini(struct intel_panel *panel)
 	struct intel_connector *intel_connector =
 		container_of(panel, struct intel_connector, panel);
 
+	intel_panel_destroy_backlight(panel);
+
 	if (panel->fixed_mode)
 		drm_mode_destroy(intel_connector->base.dev, panel->fixed_mode);