drm/i915: enable VT switchless resume v3

With the other bits in place, we can do this safely.

v2: disable backlight on suspend to prevent premature enablement on resume
v3: disable CRTCs on suspend to allow RTD3 (Kristen)
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.c

@@ -458,6 +458,7 @@ bool i915_semaphore_is_enabled(struct drm_device *dev)
 static int i915_drm_freeze(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct drm_crtc *crtc;
 
 	/* ignore lid events during suspend */
 	mutex_lock(&dev_priv->modeset_restore_lock);
@@ -481,10 +482,14 @@ static int i915_drm_freeze(struct drm_device *dev)
 
 		cancel_delayed_work_sync(&dev_priv->rps.delayed_resume_work);
 
-		intel_modeset_disable(dev);
-
 		drm_irq_uninstall(dev);
 		dev_priv->enable_hotplug_processing = false;
+		/*
+		 * Disable CRTCs directly since we want to preserve sw state
+		 * for _thaw.
+		 */
+		list_for_each_entry(crtc, &dev->mode_config.crtc_list, head)
+			dev_priv->display.crtc_disable(crtc);
 	}
 
 	i915_save_state(dev);
@@ -562,7 +567,10 @@ static int __i915_drm_thaw(struct drm_device *dev)
 		drm_irq_install(dev);
 
 		intel_modeset_init_hw(dev);
-		intel_modeset_setup_hw_state(dev, false);
+
+		drm_modeset_lock_all(dev);
+		intel_modeset_setup_hw_state(dev, true);
+		drm_modeset_unlock_all(dev);
 
 		/*
 		 * ... but also need to make sure that hotplug processing

drivers/gpu/drm/i915/intel_fb.c

@@ -150,6 +150,9 @@ static int intelfb_create(struct drm_fb_helper *helper,
 	}
 	info->screen_size = size;
 
+	/* This driver doesn't need a VT switch to restore the mode on resume */
+	info->skip_vt_switch = true;
+
 	drm_fb_helper_fill_fix(info, fb->pitches[0], fb->depth);
 	drm_fb_helper_fill_var(info, &ifbdev->helper, sizes->fb_width, sizes->fb_height);