drm: Replace fb_helper->atomic with mode_config->atomic_commit

Drivers transitioning to atomic might not yet want to enable full
DRIVER_ATOMIC support when it's not entirely working. But using atomic
internally makes a lot more sense earlier.

Instead of spreading such flags to more places I figured it's simpler
to just check for mode_config->funcs->atomic_commit, and use atomic
paths if that is set. For the only driver currently transitioning
(i915) this does the right thing.

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465388359-8070-23-git-send-email-daniel.vetter@ffwll.ch

drivers/gpu/drm/drm_fb_helper.c

@@ -385,7 +385,7 @@ static int restore_fbdev_mode(struct drm_fb_helper *fb_helper)
 
 	drm_warn_on_modeset_not_all_locked(dev);
 
-	if (fb_helper->atomic)
+	if (dev->mode_config.funcs->atomic_commit)
 		return restore_fbdev_mode_atomic(fb_helper);
 
 	drm_for_each_plane(plane, dev) {
@@ -716,8 +716,6 @@ int drm_fb_helper_init(struct drm_device *dev,
 		i++;
 	}
 
-	fb_helper->atomic = !!drm_core_check_feature(dev, DRIVER_ATOMIC);
-
 	return 0;
 out_free:
 	drm_fb_helper_crtc_free(fb_helper);
@@ -1344,7 +1342,7 @@ int drm_fb_helper_pan_display(struct fb_var_screeninfo *var,
 		return -EBUSY;
 	}
 
-	if (fb_helper->atomic) {
+	if (dev->mode_config.funcs->atomic_commit) {
 		ret = pan_display_atomic(var, info);
 		goto unlock;
 	}

drivers/gpu/drm/i915/intel_fbdev.c

@@ -724,8 +724,6 @@ int intel_fbdev_init(struct drm_device *dev)
 		return ret;
 	}
 
-	ifbdev->helper.atomic = true;
-
 	dev_priv->fbdev = ifbdev;
 	INIT_WORK(&dev_priv->fbdev_suspend_work, intel_fbdev_suspend_worker);
 

include/drm/drm_fb_helper.h

@@ -212,17 +212,6 @@ struct drm_fb_helper {
 	 * needs to be reprobe when fbdev is in control again.
 	 */
 	bool delayed_hotplug;
-
-	/**
-	 * @atomic:
-	 *
-	 * Use atomic updates for restore_fbdev_mode(), etc.  This defaults to
-	 * true if driver has DRIVER_ATOMIC feature flag, but drivers can
-	 * override it to true after drm_fb_helper_init() if they support atomic
-	 * modeset but do not yet advertise DRIVER_ATOMIC (note that fb-helper
-	 * does not require ASYNC commits).
-	 */
-	bool atomic;
 };
 
 #ifdef CONFIG_DRM_FBDEV_EMULATION