drm/ttm: Documentation update

Remove an obsolete comment about mm nodes.
Document the new bo range manager interface.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

2 files changed, 74 insertions, 13 deletions

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index a1cb783c7131..cf47978cf0e2 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -27,14 +27,6 @@
 /*
  * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
  */
-/* Notes:
- *
- * We store bo pointer in drm_mm_node struct so we know which bo own a
- * specific node. There is no protection on the pointer, thus to make
- * sure things don't go berserk you have to access this pointer while
- * holding the global lru lock and make sure anytime you free a node you
- * reset the pointer to NULL.
- */
 
 #include "ttm/ttm_module.h"
 #include "ttm/ttm_bo_driver.h"
diff --git a/include/drm/ttm/ttm_bo_driver.h b/include/drm/ttm/ttm_bo_driver.h
index d01b4ddbdc56..8e0c848326b6 100644
--- a/include/drm/ttm/ttm_bo_driver.h
+++ b/include/drm/ttm/ttm_bo_driver.h
@@ -206,14 +206,84 @@ struct ttm_tt {
 struct ttm_mem_type_manager;
 
 struct ttm_mem_type_manager_func {
+        /**
+         * struct ttm_mem_type_manager member init
+         *
+         * @man: Pointer to a memory type manager.
+         * @p_size: Implementation dependent, but typically the size of the
+         * range to be managed in pages.
+         *
+         * Called to initialize a private range manager. The function is
+         * expected to initialize the man::priv member.
+         * Returns 0 on success, negative error code on failure.
+         */
         int  (*init)(struct ttm_mem_type_manager *man, unsigned long p_size);
+
+        /**
+         * struct ttm_mem_type_manager member takedown
+         *
+         * @man: Pointer to a memory type manager.
+         *
+         * Called to undo the setup done in init. All allocated resources
+         * should be freed.
+         */
         int  (*takedown)(struct ttm_mem_type_manager *man);
+
+        /**
+         * struct ttm_mem_type_manager member get_node
+         *
+         * @man: Pointer to a memory type manager.
+         * @bo: Pointer to the buffer object we're allocating space for.
+         * @placement: Placement details.
+         * @mem: Pointer to a struct ttm_mem_reg to be filled in.
+         *
+         * This function should allocate space in the memory type managed
+         * by @man. Placement details if
+         * applicable are given by @placement. If successful,
+         * @mem::mm_node should be set to a non-null value, and
+         * @mem::start should be set to a value identifying the beginning
+         * of the range allocated, and the function should return zero.
+         * If the memory region accomodate the buffer object, @mem::mm_node
+         * should be set to NULL, and the function should return 0.
+         * If a system error occured, preventing the request to be fulfilled,
+         * the function should return a negative error code.
+         *
+         * Note that @mem::mm_node will only be dereferenced by
+         * struct ttm_mem_type_manager functions and optionally by the driver,
+         * which has knowledge of the underlying type.
+         *
+         * This function may not be called from within atomic context, so
+         * an implementation can and must use either a mutex or a spinlock to
+         * protect any data structures managing the space.
+         */
         int  (*get_node)(struct ttm_mem_type_manager *man,
                          struct ttm_buffer_object *bo,
                          struct ttm_placement *placement,
                          struct ttm_mem_reg *mem);
+
+        /**
+         * struct ttm_mem_type_manager member put_node
+         *
+         * @man: Pointer to a memory type manager.
+         * @mem: Pointer to a struct ttm_mem_reg to be filled in.
+         *
+         * This function frees memory type resources previously allocated
+         * and that are identified by @mem::mm_node and @mem::start. May not
+         * be called from within atomic context.
+         */
         void (*put_node)(struct ttm_mem_type_manager *man,
                          struct ttm_mem_reg *mem);
+
+        /**
+         * struct ttm_mem_type_manager member debug
+         *
+         * @man: Pointer to a memory type manager.
+         * @prefix: Prefix to be used in printout to identify the caller.
+         *
+         * This function is called to print out the state of the memory
+         * type manager to aid debugging of out-of-memory conditions.
+         * It may not be called from within atomic context.
+         */
         void (*debug)(struct ttm_mem_type_manager *man, const char *prefix);
 };
 
@@ -231,14 +301,13 @@ struct ttm_mem_type_manager {
         uint64_t size;
         uint32_t available_caching;
         uint32_t default_caching;
+        const struct ttm_mem_type_manager_func *func;
+        void *priv;
 
         /*
-         * Protected by the bdev->lru_lock.
-         * TODO: Consider one lru_lock per ttm_mem_type_manager.
-         * Plays ill with list removal, though.
+         * Protected by the global->lru_lock.
          */
-        const struct ttm_mem_type_manager_func *func;
-        void *priv;
+
         struct list_head lru;
 };