drm/i915: restore only the mode of this driver on lastclose (v2)

i915 calls the panic handler function on last close to reset the modes,
however this is a really bad idea for multi-gpu machines, esp shareable
gpus machines. So add a new entry point for the driver to just restore
its own fbcon mode.

v2: move code into fb helper, fix panic code to block mode change on
powered off GPUs.

[airlied: this hits drm core and I wrote it and it was reviewed on intel-gfx
 so really I signed it off twice ;-).]
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_fb_helper.c

@@ -342,22 +342,35 @@ int drm_fb_helper_debug_leave(struct fb_info *info)
 }
 EXPORT_SYMBOL(drm_fb_helper_debug_leave);
 
+bool drm_fb_helper_restore_fbdev_mode(struct drm_fb_helper *fb_helper)
+{
+	bool error = false;
+	int i, ret;
+	for (i = 0; i < fb_helper->crtc_count; i++) {
+		struct drm_mode_set *mode_set = &fb_helper->crtc_info[i].mode_set;
+		ret = drm_crtc_helper_set_config(mode_set);
+		if (ret)
+			error = true;
+	}
+	return error;
+}
+EXPORT_SYMBOL(drm_fb_helper_restore_fbdev_mode);
+
 bool drm_fb_helper_force_kernel_mode(void)
 {
-	int i = 0;
 	bool ret, error = false;
 	struct drm_fb_helper *helper;
 
 	if (list_empty(&kernel_fb_helper_list))
 		return false;
 
 	list_for_each_entry(helper, &kernel_fb_helper_list, kernel_fb_list) {
-		for (i = 0; i < helper->crtc_count; i++) {
-			struct drm_mode_set *mode_set = &helper->crtc_info[i].mode_set;
-			ret = drm_crtc_helper_set_config(mode_set);
-			if (ret)
-				error = true;
-		}
+		if (helper->dev->switch_power_state == DRM_SWITCH_POWER_OFF)
+			continue;
+
+		ret = drm_fb_helper_restore_fbdev_mode(helper);
+		if (ret)
+			error = true;
 	}
 	return error;
 }

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 +264,13 @@ 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)
+{
+	int ret;
+	drm_i915_private_t *dev_priv = dev->dev_private;
+
+	ret = drm_fb_helper_restore_fbdev_mode(&dev_priv->fbdev->helper);
+	if (ret)
+		DRM_DEBUG("failed to restore crtc mode\n");
+}

include/drm/drm_fb_helper.h

@@ -118,6 +118,7 @@ int drm_fb_helper_setcolreg(unsigned regno,
 			    unsigned transp,
 			    struct fb_info *info);
 
+bool drm_fb_helper_restore_fbdev_mode(struct drm_fb_helper *fb_helper);
 void drm_fb_helper_restore(void);
 void drm_fb_helper_fill_var(struct fb_info *info, struct drm_fb_helper *fb_helper,
 			    uint32_t fb_width, uint32_t fb_height);