i915: restore only the mode of this driver on lastclose

This has always used a big hammer, but that hammer is probably
too big, I'm also not sure its necessary but at least this
should be safe.

Should fix: https://bugzilla.kernel.org/show_bug.cgi?id=23592

Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/i915/i915_dma.c

@@ -2207,7 +2207,7 @@ void i915_driver_lastclose(struct drm_device * dev)
 	drm_i915_private_t *dev_priv = dev->dev_private;
 
 	if (!dev_priv || drm_core_check_feature(dev, DRIVER_MODESET)) {
-		drm_fb_helper_restore();
+		intel_fb_restore_mode(dev);
 		vga_switcheroo_process_delayed_switch();
 		return;
 	}

drivers/gpu/drm/i915/intel_drv.h

@@ -338,4 +338,5 @@ extern int intel_overlay_attrs(struct drm_device *dev, void *data,
 			       struct drm_file *file_priv);
 
 extern void intel_fb_output_poll_changed(struct drm_device *dev);
+extern void intel_fb_restore_mode(struct drm_device *dev);
 #endif /* __INTEL_DRV_H__ */

drivers/gpu/drm/i915/intel_fb.c

@@ -264,3 +264,19 @@ void intel_fb_output_poll_changed(struct drm_device *dev)
 	drm_i915_private_t *dev_priv = dev->dev_private;
 	drm_fb_helper_hotplug_event(&dev_priv->fbdev->helper);
 }
+
+void intel_fb_restore_mode(struct drm_device *dev)
+{
+	drm_i915_private_t *dev_priv = dev->dev_private;
+	int ret, i;
+
+	if (!dev_priv->fbdev)
+		return;
+
+	for (i = 0; i < dev_priv->fbdev->helper.crtc_count; i++) {
+		struct drm_mode_set *mode_set = &dev_priv->fbdev->helper.crtc_info[i].mode_set;
+		ret = drm_crtc_helper_set_config(mode_set);
+		if (ret)
+			DRM_DEBUG("failed to restore crtc mode\n");
+	}
+}