drm: Resurrect atomic rmfb code

This was somehow lost between v3 and the merged version in Maarten's
patch merged as:

commit f2d580b9
Author: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Date:   Wed May 4 14:38:26 2016 +0200

    drm/core: Do not preserve framebuffer on rmfb, v4.

Actual code copied from Maarten's patch, but with the slight change to
just use dev->mode_config.funcs->atomic_commit to decide whether to
use the atomic path or not.

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1465388359-8070-24-git-send-email-daniel.vetter@ffwll.ch

drivers/gpu/drm/drm_atomic.c

@@ -1564,6 +1564,72 @@ void drm_atomic_clean_old_fb(struct drm_device *dev,
 }
 EXPORT_SYMBOL(drm_atomic_clean_old_fb);
 
+int drm_atomic_remove_fb(struct drm_framebuffer *fb)
+{
+	struct drm_modeset_acquire_ctx ctx;
+	struct drm_device *dev = fb->dev;
+	struct drm_atomic_state *state;
+	struct drm_plane *plane;
+	int ret = 0;
+	unsigned plane_mask;
+
+	state = drm_atomic_state_alloc(dev);
+	if (!state)
+		return -ENOMEM;
+
+	drm_modeset_acquire_init(&ctx, 0);
+	state->acquire_ctx = &ctx;
+
+retry:
+	plane_mask = 0;
+	ret = drm_modeset_lock_all_ctx(dev, &ctx);
+	if (ret)
+		goto unlock;
+
+	drm_for_each_plane(plane, dev) {
+		struct drm_plane_state *plane_state;
+
+		if (plane->state->fb != fb)
+			continue;
+
+		plane_state = drm_atomic_get_plane_state(state, plane);
+		if (IS_ERR(plane_state)) {
+			ret = PTR_ERR(plane_state);
+			goto unlock;
+		}
+
+		drm_atomic_set_fb_for_plane(plane_state, NULL);
+		ret = drm_atomic_set_crtc_for_plane(plane_state, NULL);
+		if (ret)
+			goto unlock;
+
+		plane_mask |= BIT(drm_plane_index(plane));
+
+		plane->old_fb = plane->fb;
+		plane->fb = NULL;
+	}
+
+	if (plane_mask)
+		ret = drm_atomic_commit(state);
+
+unlock:
+	if (plane_mask)
+		drm_atomic_clean_old_fb(dev, plane_mask, ret);
+
+	if (ret == -EDEADLK) {
+		drm_modeset_backoff(&ctx);
+		goto retry;
+	}
+
+	if (ret || !plane_mask)
+		drm_atomic_state_free(state);
+
+	drm_modeset_drop_locks(&ctx);
+	drm_modeset_acquire_fini(&ctx);
+
+	return ret;
+}
+
 int drm_mode_atomic_ioctl(struct drm_device *dev,
 			  void *data, struct drm_file *file_priv)
 {

drivers/gpu/drm/drm_crtc.c

@@ -613,6 +613,11 @@ void drm_framebuffer_remove(struct drm_framebuffer *fb)
 	 * in this manner.
 	 */
 	if (drm_framebuffer_read_refcount(fb) > 1) {
+		if (dev->mode_config.funcs->atomic_commit) {
+			drm_atomic_remove_fb(fb);
+			goto out;
+		}
+
 		drm_modeset_lock_all(dev);
 		/* remove from any CRTC */
 		drm_for_each_crtc(crtc, dev) {
@@ -630,6 +635,7 @@ void drm_framebuffer_remove(struct drm_framebuffer *fb)
 		drm_modeset_unlock_all(dev);
 	}
 
+out:
 	drm_framebuffer_unreference(fb);
 }
 EXPORT_SYMBOL(drm_framebuffer_remove);

drivers/gpu/drm/drm_crtc_internal.h

@@ -125,6 +125,7 @@ int drm_atomic_get_property(struct drm_mode_object *obj,
 			    struct drm_property *property, uint64_t *val);
 int drm_mode_atomic_ioctl(struct drm_device *dev,
 			  void *data, struct drm_file *file_priv);
+int drm_atomic_remove_fb(struct drm_framebuffer *fb);
 
 int drm_modeset_register_all(struct drm_device *dev);
 void drm_modeset_unregister_all(struct drm_device *dev);