drm/armada: use a private mutex to protect priv->linear

Reusing the Big DRM Lock just leaks, and the few things left that
dev->struct_mutex protected are very well contained - it's just the
linear drm_mm manager.

With this armada is completely struct_mutex free!

v2: Convert things properly and also take the lock in
armada_gem_free_object, and remove the stale comment (Russell).

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

drivers/gpu/drm/armada/armada_debugfs.c

@@ -21,9 +21,9 @@ static int armada_debugfs_gem_linear_show(struct seq_file *m, void *data)
 	struct armada_private *priv = dev->dev_private;
 	int ret;
 
-	mutex_lock(&dev->struct_mutex);
+	mutex_lock(&priv->linear_lock);
 	ret = drm_mm_dump_table(m, &priv->linear);
-	mutex_unlock(&dev->struct_mutex);
+	mutex_unlock(&priv->linear_lock);
 
 	return ret;
 }

drivers/gpu/drm/armada/armada_drm.h

@@ -57,7 +57,8 @@ struct armada_private {
 	DECLARE_KFIFO(fb_unref, struct drm_framebuffer *, 8);
 	struct drm_fb_helper	*fbdev;
 	struct armada_crtc	*dcrtc[2];
-	struct drm_mm		linear;
+	struct drm_mm		linear; /* protected by linear_lock */
+	struct mutex		linear_lock;
 	struct drm_property	*csc_yuv_prop;
 	struct drm_property	*csc_rgb_prop;
 	struct drm_property	*colorkey_prop;

drivers/gpu/drm/armada/armada_drv.c

@@ -101,6 +101,7 @@ static int armada_drm_load(struct drm_device *dev, unsigned long flags)
 	dev->mode_config.preferred_depth = 24;
 	dev->mode_config.funcs = &armada_drm_mode_config_funcs;
 	drm_mm_init(&priv->linear, mem->start, resource_size(mem));
+	mutex_init(&priv->linear_lock);
 
 	ret = component_bind_all(dev->dev, dev);
 	if (ret)

drivers/gpu/drm/armada/armada_gem.c

@@ -46,22 +46,26 @@ static size_t roundup_gem_size(size_t size)
 	return roundup(size, PAGE_SIZE);
 }
 
-/* dev->struct_mutex is held here */
 void armada_gem_free_object(struct drm_gem_object *obj)
 {
 	struct armada_gem_object *dobj = drm_to_armada_gem(obj);
+	struct armada_private *priv = obj->dev->dev_private;
 
 	DRM_DEBUG_DRIVER("release obj %p\n", dobj);
 
 	drm_gem_free_mmap_offset(&dobj->obj);
 
+	might_lock(&priv->linear_lock);
+
 	if (dobj->page) {
 		/* page backed memory */
 		unsigned int order = get_order(dobj->obj.size);
 		__free_pages(dobj->page, order);
 	} else if (dobj->linear) {
 		/* linear backed memory */
+		mutex_lock(&priv->linear_lock);
 		drm_mm_remove_node(dobj->linear);
+		mutex_unlock(&priv->linear_lock);
 		kfree(dobj->linear);
 		if (dobj->addr)
 			iounmap(dobj->addr);
@@ -144,10 +148,10 @@ armada_gem_linear_back(struct drm_device *dev, struct armada_gem_object *obj)
 		if (!node)
 			return -ENOSPC;
 
-		mutex_lock(&dev->struct_mutex);
+		mutex_lock(&priv->linear_lock);
 		ret = drm_mm_insert_node(&priv->linear, node, size, align,
 					 DRM_MM_SEARCH_DEFAULT);
-		mutex_unlock(&dev->struct_mutex);
+		mutex_unlock(&priv->linear_lock);
 		if (ret) {
 			kfree(node);
 			return ret;
@@ -158,9 +162,9 @@ armada_gem_linear_back(struct drm_device *dev, struct armada_gem_object *obj)
 		/* Ensure that the memory we're returning is cleared. */
 		ptr = ioremap_wc(obj->linear->start, size);
 		if (!ptr) {
-			mutex_lock(&dev->struct_mutex);
+			mutex_lock(&priv->linear_lock);
 			drm_mm_remove_node(obj->linear);
-			mutex_unlock(&dev->struct_mutex);
+			mutex_unlock(&priv->linear_lock);
 			kfree(obj->linear);
 			obj->linear = NULL;
 			return -ENOMEM;