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drm/mm: Some doc polish

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Added some boilerplate for the structs, documented members where they
are relevant and plenty of markup for hyperlinks all over. And a few
small wording polish.

Note that the intro needs some more love after the DRM_MM_INSERT_*
patch from Chris has landed.

v2: Spelling fixes (Chris).

v3: Use &struct foo instead of &foo structure (Chris).

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1483044517-5770-3-git-send-email-daniel.vetter@ffwll.ch
This commit is contained in:
Daniel Vetter 2016-12-29 21:48:23 +01:00
parent a818286343
commit 05fc03217e
3 changed files with 89 additions and 38 deletions
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2
Documentation/gpu/drm-mm.rst
View File

@ -449,7 +449,7 @@ LRU Scan/Eviction Support
-------------------------
.. kernel-doc:: drivers/gpu/drm/drm_mm.c
:doc: lru scan roaster
:doc: lru scan roster
DRM MM Range Allocator Function References
------------------------------------------

41
drivers/gpu/drm/drm_mm.c
View File

@ -59,8 +59,8 @@
*
* The main data struct is &drm_mm, allocations are tracked in &drm_mm_node.
* Drivers are free to embed either of them into their own suitable
* datastructures. drm_mm itself will not do any allocations of its own, so if
* drivers choose not to embed nodes they need to still allocate them
* datastructures. drm_mm itself will not do any memory allocations of its own,
* so if drivers choose not to embed nodes they need to still allocate them
* themselves.
*
* The range allocator also supports reservation of preallocated blocks. This is
@ -78,7 +78,7 @@
* steep cliff not a real concern. Removing a node again is O(1).
*
* drm_mm supports a few features: Alignment and range restrictions can be
* supplied. Further more every &drm_mm_node has a color value (which is just an
* supplied. Furthermore every &drm_mm_node has a color value (which is just an
* opaque unsigned long) which in conjunction with a driver callback can be used
* to implement sophisticated placement restrictions. The i915 DRM driver uses
* this to implement guard pages between incompatible caching domains in the
@ -296,11 +296,11 @@ static void drm_mm_insert_helper(struct drm_mm_node *hole_node,
* @mm: drm_mm allocator to insert @node into
* @node: drm_mm_node to insert
*
* This functions inserts an already set-up drm_mm_node into the allocator,
* meaning that start, size and color must be set by the caller. This is useful
* to initialize the allocator with preallocated objects which must be set-up
* before the range allocator can be set-up, e.g. when taking over a firmware
* framebuffer.
* This functions inserts an already set-up &drm_mm_node into the allocator,
* meaning that start, size and color must be set by the caller. All other
* fields must be cleared to 0. This is useful to initialize the allocator with
* preallocated objects which must be set-up before the range allocator can be
* set-up, e.g. when taking over a firmware framebuffer.
*
* Returns:
* 0 on success, -ENOSPC if there's no hole where @node is.
@ -375,7 +375,7 @@ EXPORT_SYMBOL(drm_mm_reserve_node);
* @sflags: flags to fine-tune the allocation search
* @aflags: flags to fine-tune the allocation behavior
*
* The preallocated node must be cleared to 0.
* The preallocated @node must be cleared to 0.
*
* Returns:
* 0 on success, -ENOSPC if there's no suitable hole.
@ -537,7 +537,7 @@ void drm_mm_replace_node(struct drm_mm_node *old, struct drm_mm_node *new)
EXPORT_SYMBOL(drm_mm_replace_node);
/**
* DOC: lru scan roaster
* DOC: lru scan roster
*
* Very often GPUs need to have continuous allocations for a given object. When
* evicting objects to make space for a new one it is therefore not most
@ -549,9 +549,11 @@ EXPORT_SYMBOL(drm_mm_replace_node);
* The DRM range allocator supports this use-case through the scanning
* interfaces. First a scan operation needs to be initialized with
* drm_mm_scan_init() or drm_mm_scan_init_with_range(). The driver adds
* objects to the roster (probably by walking an LRU list, but this can be
* freely implemented) (using drm_mm_scan_add_block()) until a suitable hole
* is found or there are no further evictable objects.
* objects to the roster, probably by walking an LRU list, but this can be
* freely implemented. Eviction candiates are added using
* drm_mm_scan_add_block() until a suitable hole is found or there are no
* further evictable objects. Eviction roster metadata is tracked in struct
* &drm_mm_scan.
*
* The driver must walk through all objects again in exactly the reverse
* order to restore the allocator state. Note that while the allocator is used
@ -559,7 +561,7 @@ EXPORT_SYMBOL(drm_mm_replace_node);
*
* Finally the driver evicts all objects selected (drm_mm_scan_remove_block()
* reported true) in the scan, and any overlapping nodes after color adjustment
* (drm_mm_scan_evict_color()). Adding and removing an object is O(1), and
* (drm_mm_scan_color_evict()). Adding and removing an object is O(1), and
* since freeing a node is also O(1) the overall complexity is
* O(scanned_objects). So like the free stack which needs to be walked before a
* scan operation even begins this is linear in the number of objects. It
@ -705,14 +707,15 @@ EXPORT_SYMBOL(drm_mm_scan_add_block);
* @scan: the active drm_mm scanner
* @node: drm_mm_node to remove
*
* Nodes _must_ be removed in exactly the reverse order from the scan list as
* they have been added (e.g. using list_add as they are added and then
* list_for_each over that eviction list to remove), otherwise the internal
* Nodes **must** be removed in exactly the reverse order from the scan list as
* they have been added (e.g. using list_add() as they are added and then
* list_for_each() over that eviction list to remove), otherwise the internal
* state of the memory manager will be corrupted.
*
* When the scan list is empty, the selected memory nodes can be freed. An
* immediately following drm_mm_search_free with !DRM_MM_SEARCH_BEST will then
* return the just freed block (because its at the top of the free_stack list).
* immediately following drm_mm_insert_node_in_range_generic() or one of the
* simpler versions of that function with !DRM_MM_SEARCH_BEST will then return
* the just freed block (because its at the top of the free_stack list).
*
* Returns:
* True if this block should be evicted, false otherwise. Will always

84
include/drm/drm_mm.h
View File

@ -67,16 +67,29 @@ enum drm_mm_allocator_flags {
#define DRM_MM_BOTTOMUP DRM_MM_SEARCH_DEFAULT, DRM_MM_CREATE_DEFAULT
#define DRM_MM_TOPDOWN DRM_MM_SEARCH_BELOW, DRM_MM_CREATE_TOP
/**
* struct drm_mm_node - allocated block in the DRM allocator
*
* This represents an allocated block in a &drm_mm allocator. Except for
* pre-reserved nodes inserted using drm_mm_reserve_node() the structure is
* entirely opaque and should only be accessed through the provided funcions.
* Since allocation of these nodes is entirely handled by the driver they can be
* embedded.
*/
struct drm_mm_node {
/** @color: Opaque driver-private tag. */
unsigned long color;
/** @start: Start address of the allocated block. */
u64 start;
/** @size: Size of the allocated block. */
u64 size;
/* private: */
struct list_head node_list;
struct list_head hole_stack;
struct rb_node rb;
unsigned hole_follows : 1;
unsigned allocated : 1;
bool scanned_block : 1;
unsigned long color;
u64 start;
u64 size;
u64 __subtree_last;
struct drm_mm *mm;
#ifdef CONFIG_DRM_DEBUG_MM
@ -84,7 +97,29 @@ struct drm_mm_node {
#endif
};
/**
* struct drm_mm - DRM allocator
*
* DRM range allocator with a few special functions and features geared towards
* managing GPU memory. Except for the @color_adjust callback the structure is
* entirely opaque and should only be accessed through the provided functions
* and macros. This structure can be embedded into larger driver structures.
*/
struct drm_mm {
/**
* @color_adjust:
*
* Optional driver callback to further apply restrictions on a hole. The
* node argument points at the node containing the hole from which the
* block would be allocated (see drm_mm_hole_follows() and friends). The
* other arguments are the size of the block to be allocated. The driver
* can adjust the start and end as needed to e.g. insert guard pages.
*/
void (*color_adjust)(const struct drm_mm_node *node,
unsigned long color,
u64 *start, u64 *end);
/* private: */
/* List of all memory nodes that immediately precede a free hole. */
struct list_head hole_stack;
/* head_node.node_list is the list of all memory nodes, ordered
@ -93,14 +128,20 @@ struct drm_mm {
/* Keep an interval_tree for fast lookup of drm_mm_nodes by address. */
struct rb_root interval_tree;
void (*color_adjust)(const struct drm_mm_node *node,
unsigned long color,
u64 *start, u64 *end);
unsigned long scan_active;
};
/**
* struct drm_mm_scan - DRM allocator eviction roaster data
*
* This structure tracks data needed for the eviction roaster set up using
* drm_mm_scan_init(), and used with drm_mm_scan_add_block() and
* drm_mm_scan_remove_block(). The structure is entirely opaque and should only
* be accessed through the provided functions and macros. It is meant to be
* allocated temporarily by the driver on the stack.
*/
struct drm_mm_scan {
/* private: */
struct drm_mm *mm;
u64 size;
@ -159,7 +200,8 @@ static inline bool drm_mm_initialized(const struct drm_mm *mm)
*
* Holes are embedded into the drm_mm using the tail of a drm_mm_node.
* If you wish to know whether a hole follows this particular node,
* query this function.
* query this function. See also drm_mm_hole_node_start() and
* drm_mm_hole_node_end().
*
* Returns:
* True if a hole follows the @node.
@ -228,23 +270,23 @@ static inline u64 drm_mm_hole_node_end(const struct drm_mm_node *hole_node)
/**
* drm_mm_for_each_node - iterator to walk over all allocated nodes
* @entry: drm_mm_node structure to assign to in each iteration step
* @mm: drm_mm allocator to walk
* @entry: &struct drm_mm_node to assign to in each iteration step
* @mm: &drm_mm allocator to walk
*
* This iterator walks over all nodes in the range allocator. It is implemented
* with list_for_each, so not save against removal of elements.
* with list_for_each(), so not save against removal of elements.
*/
#define drm_mm_for_each_node(entry, mm) \
list_for_each_entry(entry, drm_mm_nodes(mm), node_list)
/**
* drm_mm_for_each_node_safe - iterator to walk over all allocated nodes
* @entry: drm_mm_node structure to assign to in each iteration step
* @next: drm_mm_node structure to store the next step
* @mm: drm_mm allocator to walk
* @entry: &struct drm_mm_node to assign to in each iteration step
* @next: &struct drm_mm_node to store the next step
* @mm: &drm_mm allocator to walk
*
* This iterator walks over all nodes in the range allocator. It is implemented
* with list_for_each_safe, so save against removal of elements.
* with list_for_each_safe(), so save against removal of elements.
*/
#define drm_mm_for_each_node_safe(entry, next, mm) \
list_for_each_entry_safe(entry, next, drm_mm_nodes(mm), node_list)
@ -259,13 +301,13 @@ static inline u64 drm_mm_hole_node_end(const struct drm_mm_node *hole_node)
/**
* drm_mm_for_each_hole - iterator to walk over all holes
* @entry: drm_mm_node used internally to track progress
* @mm: drm_mm allocator to walk
* @entry: &drm_mm_node used internally to track progress
* @mm: &drm_mm allocator to walk
* @hole_start: ulong variable to assign the hole start to on each iteration
* @hole_end: ulong variable to assign the hole end to on each iteration
*
* This iterator walks over all holes in the range allocator. It is implemented
* with list_for_each, so not save against removal of elements. @entry is used
* with list_for_each(), so not save against removal of elements. @entry is used
* internally and will not reflect a real drm_mm_node for the very first hole.
* Hence users of this iterator may not access it.
*
@ -334,6 +376,9 @@ static inline int drm_mm_insert_node_in_range(struct drm_mm *mm,
* @sflags: flags to fine-tune the allocation search
* @aflags: flags to fine-tune the allocation behavior
*
* This is a simplified version of drm_mm_insert_node_in_range_generic() with no
* range restrictions applied.
*
* The preallocated node must be cleared to 0.
*
* Returns:
@ -434,6 +479,9 @@ void drm_mm_scan_init_with_range(struct drm_mm_scan *scan,
* @color: opaque tag value to use for the allocation
* @flags: flags to specify how the allocation will be performed afterwards
*
* This is a simplified version of drm_mm_scan_init_with_range() with no range
* restrictions applied.
*
* This simply sets up the scanning routines with the parameters for the desired
* hole.
*