drm/ttm: use a static ttm_bo_global instance

As the name says we only need one global instance of ttm_bo_global.

Just use a single exported instance which is save to initialize multiple times.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/ttm/ttm_bo.c

@@ -49,6 +49,9 @@ static void ttm_bo_global_kobj_release(struct kobject *kobj);
  * ttm_global_mutex - protecting the global BO state
  */
 DEFINE_MUTEX(ttm_global_mutex);
+struct ttm_bo_global ttm_bo_glob = {
+	.use_count = 0
+};
 
 static struct attribute ttm_bo_count = {
 	.name = "bo_count",
@@ -1527,22 +1530,35 @@ static void ttm_bo_global_kobj_release(struct kobject *kobj)
 	kfree(glob);
 }
 
-void ttm_bo_global_release(struct ttm_bo_global *glob)
+void ttm_bo_global_release(void)
 {
+	struct ttm_bo_global *glob = &ttm_bo_glob;
+
+	mutex_lock(&ttm_global_mutex);
+	if (--glob->use_count > 0)
+		goto out;
+
 	kobject_del(&glob->kobj);
 	kobject_put(&glob->kobj);
 	ttm_mem_global_release(&ttm_mem_glob);
+out:
+	mutex_unlock(&ttm_global_mutex);
 }
 EXPORT_SYMBOL(ttm_bo_global_release);
 
-int ttm_bo_global_init(struct ttm_bo_global *glob)
+int ttm_bo_global_init(void)
 {
-	int ret;
+	struct ttm_bo_global *glob = &ttm_bo_glob;
+	int ret = 0;
 	unsigned i;
 
+	mutex_lock(&ttm_global_mutex);
+	if (++glob->use_count > 1)
+		goto out;
+
 	ret = ttm_mem_global_init(&ttm_mem_glob);
 	if (ret)
-		return ret;
+		goto out;
 
 	spin_lock_init(&glob->lru_lock);
 	glob->mem_glob = &ttm_mem_glob;
@@ -1551,7 +1567,7 @@ int ttm_bo_global_init(struct ttm_bo_global *glob)
 
 	if (unlikely(glob->dummy_read_page == NULL)) {
 		ret = -ENOMEM;
-		goto out_no_drp;
+		goto out;
 	}
 
 	for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i)
@@ -1563,9 +1579,8 @@ int ttm_bo_global_init(struct ttm_bo_global *glob)
 		&glob->kobj, &ttm_bo_glob_kobj_type, ttm_get_kobj(), "buffer_objects");
 	if (unlikely(ret != 0))
 		kobject_put(&glob->kobj);
-	return ret;
-out_no_drp:
-	kfree(glob);
+out:
+	mutex_unlock(&ttm_global_mutex);
 	return ret;
 }
 EXPORT_SYMBOL(ttm_bo_global_init);

include/drm/ttm/ttm_bo_driver.h

@@ -398,7 +398,7 @@ struct ttm_bo_driver {
  * @swap_lru: Lru list of buffer objects used for swapping.
  */
 
-struct ttm_bo_global {
+extern struct ttm_bo_global {
 
 	/**
 	 * Constant after init.
@@ -410,8 +410,9 @@ struct ttm_bo_global {
 	spinlock_t lru_lock;
 
 	/**
-	 * Protected by device_list_mutex.
+	 * Protected by ttm_global_mutex.
 	 */
+	unsigned int use_count;
 	struct list_head device_list;
 
 	/**
@@ -423,7 +424,7 @@ struct ttm_bo_global {
 	 * Internal protection.
 	 */
 	atomic_t bo_count;
-};
+} ttm_bo_glob;
 
 
 #define TTM_NUM_MEM_TYPES 8
@@ -568,8 +569,8 @@ void ttm_bo_mem_put(struct ttm_buffer_object *bo, struct ttm_mem_reg *mem);
 void ttm_bo_mem_put_locked(struct ttm_buffer_object *bo,
 			   struct ttm_mem_reg *mem);
 
-void ttm_bo_global_release(struct ttm_bo_global *glob);
-int ttm_bo_global_init(struct ttm_bo_global *glob);
+void ttm_bo_global_release(void);
+int ttm_bo_global_init(void);
 
 int ttm_bo_device_release(struct ttm_bo_device *bdev);
 
@@ -906,7 +907,7 @@ struct ttm_bo_global_ref {
  */
 static inline int ttm_bo_global_ref_init(struct drm_global_reference *ref)
 {
-	return ttm_bo_global_init(ref->object);
+	return ttm_bo_global_init();
 }
 
 /**
@@ -920,7 +921,7 @@ static inline int ttm_bo_global_ref_init(struct drm_global_reference *ref)
  */
 static inline void ttm_bo_global_ref_release(struct drm_global_reference *ref)
 {
-	ttm_bo_global_release(ref->object);
+	ttm_bo_global_release();
 }
 
 #endif