drm/panfrost: Add the panfrost_gem_mapping concept

With the introduction of per-FD address space, the same BO can be mapped
in different address space if the BO is globally visible (GEM_FLINK)
and opened in different context or if the dmabuf is self-imported. The
current implementation does not take case into account, and attaches the
mapping directly to the panfrost_gem_object.

Let's create a panfrost_gem_mapping struct and allow multiple mappings
per BO.

The mappings are refcounted which helps solve another problem where
mappings were torn down (GEM handle closed by userspace) while GPU
jobs accessing those BOs were still in-flight. Jobs now keep a
reference on the mappings they use.

v2 (robh):
- Minor review comment clean-ups from Steven
- Use list_is_singular helper
- Just WARN if we add a mapping when madvise state is not WILLNEED.
  With that, drop the use of object_name_lock.

v3 (robh):
- Revert returning list iterator in panfrost_gem_mapping_get()

Fixes: a5efb4c9a562 ("drm/panfrost: Restructure the GEM object creation")
Fixes: 7282f7645d06 ("drm/panfrost: Implement per FD address spaces")
Cc: <stable@vger.kernel.org>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200116021554.15090-1-robh@kernel.org

1 files changed, 35 insertions, 6 deletions

diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.h b/drivers/gpu/drm/panfrost/panfrost_gem.h
index 4b17e7308764..ca1bc9019600 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gem.h
+++ b/drivers/gpu/drm/panfrost/panfrost_gem.h
@@ -13,23 +13,46 @@ struct panfrost_gem_object {
 	struct drm_gem_shmem_object base;
 	struct sg_table *sgts;
 
-	struct panfrost_mmu *mmu;
-	struct drm_mm_node node;
-	bool is_mapped		:1;
+	/*
+	 * Use a list for now. If searching a mapping ever becomes the
+	 * bottleneck, we should consider using an RB-tree, or even better,
+	 * let the core store drm_gem_object_mapping entries (where we
+	 * could place driver specific data) instead of drm_gem_object ones
+	 * in its drm_file->object_idr table.
+	 *
+	 * struct drm_gem_object_mapping {
+	 *	struct drm_gem_object *obj;
+	 *	void *driver_priv;
+	 * };
+	 */
+	struct {
+		struct list_head list;
+		struct mutex lock;
+	} mappings;
+
 	bool noexec		:1;
 	bool is_heap		:1;
 };
 
+struct panfrost_gem_mapping {
+	struct list_head node;
+	struct kref refcount;
+	struct panfrost_gem_object *obj;
+	struct drm_mm_node mmnode;
+	struct panfrost_mmu *mmu;
+	bool active		:1;
+};
+
 static inline
 struct  panfrost_gem_object *to_panfrost_bo(struct drm_gem_object *obj)
 {
 	return container_of(to_drm_gem_shmem_obj(obj), struct panfrost_gem_object, base);
 }
 
-static inline
-struct  panfrost_gem_object *drm_mm_node_to_panfrost_bo(struct drm_mm_node *node)
+static inline struct panfrost_gem_mapping *
+drm_mm_node_to_panfrost_mapping(struct drm_mm_node *node)
 {
-	return container_of(node, struct panfrost_gem_object, node);
+	return container_of(node, struct panfrost_gem_mapping, mmnode);
 }
 
 struct drm_gem_object *panfrost_gem_create_object(struct drm_device *dev, size_t size);
@@ -49,6 +72,12 @@ int panfrost_gem_open(struct drm_gem_object *obj, struct drm_file *file_priv);
 void panfrost_gem_close(struct drm_gem_object *obj,
 			struct drm_file *file_priv);
 
+struct panfrost_gem_mapping *
+panfrost_gem_mapping_get(struct panfrost_gem_object *bo,
+			 struct panfrost_file_priv *priv);
+void panfrost_gem_mapping_put(struct panfrost_gem_mapping *mapping);
+void panfrost_gem_teardown_mappings(struct panfrost_gem_object *bo);
+
 void panfrost_gem_shrinker_init(struct drm_device *dev);
 void panfrost_gem_shrinker_cleanup(struct drm_device *dev);