drm/msm: Remove obj->gpu

It cannot be atomically updated with obj->active_count, and the only
purpose is a useless WARN_ON() (which becomes a buggy WARN_ON() once
retire_submits() is not serialized with incoming submits via
struct_mutex)
Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Signed-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/msm_gem.c

@@ -774,7 +774,6 @@ void msm_gem_active_get(struct drm_gem_object *obj, struct msm_gpu *gpu)
 
 	if (!atomic_fetch_inc(&msm_obj->active_count)) {
 		mutex_lock(&priv->mm_lock);
-		msm_obj->gpu = gpu;
 		list_del_init(&msm_obj->mm_list);
 		list_add_tail(&msm_obj->mm_list, &gpu->active_list);
 		mutex_unlock(&priv->mm_lock);
@@ -790,7 +789,6 @@ void msm_gem_active_put(struct drm_gem_object *obj)
 
 	if (!atomic_dec_return(&msm_obj->active_count)) {
 		mutex_lock(&priv->mm_lock);
-		msm_obj->gpu = NULL;
 		list_del_init(&msm_obj->mm_list);
 		list_add_tail(&msm_obj->mm_list, &priv->inactive_list);
 		mutex_unlock(&priv->mm_lock);

drivers/gpu/drm/msm/msm_gem.h

@@ -64,7 +64,6 @@ struct msm_gem_object {
 	 *
 	 */
 	struct list_head mm_list;
-	struct msm_gpu *gpu;     /* non-null if active */
 
 	/* Transiently in the process of submit ioctl, objects associated
 	 * with the submit are on submit->bo_list.. this only lasts for

drivers/gpu/drm/msm/msm_gpu.c

@@ -805,11 +805,6 @@ void msm_gpu_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
 		struct drm_gem_object *drm_obj = &msm_obj->base;
 		uint64_t iova;
 
-		/* can't happen yet.. but when we add 2d support we'll have
-		 * to deal w/ cross-ring synchronization:
-		 */
-		WARN_ON(is_active(msm_obj) && (msm_obj->gpu != gpu));
-
 		/* submit takes a reference to the bo and iova until retired: */
 		drm_gem_object_get(&msm_obj->base);
 		msm_gem_get_and_pin_iova_locked(&msm_obj->base, submit->aspace, &iova);