Commit 95ee2a8b authored by Arunpravin's avatar Arunpravin Committed by Christian König
Browse files

drm: implement a method to free unused pages 



On contiguous allocation, we round up the size
to the *next* power of 2, implement a function
to free the unused pages after the newly allocate block.

v2(Matthew Auld):
  - replace function name 'drm_buddy_free_unused_pages' with
    drm_buddy_block_trim
  - replace input argument name 'actual_size' with 'new_size'
  - add more validation checks for input arguments
  - add overlaps check to avoid needless searching and splitting
  - merged the below patch to see the feature in action
     - add free unused pages support to i915 driver
  - lock drm_buddy_block_trim() function as it calls mark_free/mark_split
    are all globally visible

v3(Matthew Auld):
  - remove trim method error handling as we address the failure case
    at drm_buddy_block_trim() function

v4:
  - in case of trim, at __alloc_range() split_block failure path
    marks the block as free and removes it from the original list,
    potentially also freeing it, to overcome this problem, we turn
    the drm_buddy_block_trim() input node into a temporary node to
    prevent recursively freeing itself, but still retain the
    un-splitting/freeing of the other nodes(Matthew Auld)

  - modify the drm_buddy_block_trim() function return type

v5(Matthew Auld):
  - revert drm_buddy_block_trim() function return type changes in v4
  - modify drm_buddy_block_trim() passing argument n_pages to original_size
    as n_pages has already been rounded up to the next power-of-two and
    passing n_pages results noop

v6:
  - fix warnings reported by kernel test robot <lkp@intel.com>

v7:
  - modify drm_buddy_block_trim() function doc description
  - at drm_buddy_block_trim() handle non-allocated block as
    a serious programmer error
  - fix a typo

Signed-off-by: default avatarArunpravin <Arunpravin.PaneerSelvam@amd.com>
Reviewed-by: default avatarMatthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220221164552.2434-3-Arunpravin.PaneerSelvam@amd.com


Signed-off-by: default avatarChristian König <christian.koenig@amd.com>
parent 476e4063

drivers/gpu/drm/drm_buddy.c

+69 −0
Original line number Diff line number Diff line
@@ -525,6 +525,75 @@ static int __drm_buddy_alloc_range(struct drm_buddy *mm, 
	return __alloc_range(mm, &dfs, start, size, blocks);

}



/**

 * drm_buddy_block_trim - free unused pages

 *

 * @mm: DRM buddy manager

 * @new_size: original size requested

 * @blocks: Input and output list of allocated blocks.

 * MUST contain single block as input to be trimmed.

 * On success will contain the newly allocated blocks

 * making up the @new_size. Blocks always appear in

 * ascending order

 *

 * For contiguous allocation, we round up the size to the nearest

 * power of two value, drivers consume *actual* size, so remaining

 * portions are unused and can be optionally freed with this function

 *

 * Returns:

 * 0 on success, error code on failure.

 */

int drm_buddy_block_trim(struct drm_buddy *mm,

			 u64 new_size,

			 struct list_head *blocks)

{

	struct drm_buddy_block *parent;

	struct drm_buddy_block *block;

	LIST_HEAD(dfs);

	u64 new_start;

	int err;



	if (!list_is_singular(blocks))

		return -EINVAL;



	block = list_first_entry(blocks,

				 struct drm_buddy_block,

				 link);



	if (WARN_ON(!drm_buddy_block_is_allocated(block)))

		return -EINVAL;



	if (new_size > drm_buddy_block_size(mm, block))

		return -EINVAL;



	if (!new_size || !IS_ALIGNED(new_size, mm->chunk_size))

		return -EINVAL;



	if (new_size == drm_buddy_block_size(mm, block))

		return 0;



	list_del(&block->link);

	mark_free(mm, block);

	mm->avail += drm_buddy_block_size(mm, block);



	/* Prevent recursively freeing this node */

	parent = block->parent;

	block->parent = NULL;



	new_start = drm_buddy_block_offset(block);

	list_add(&block->tmp_link, &dfs);

	err =  __alloc_range(mm, &dfs, new_start, new_size, blocks);

	if (err) {

		mark_allocated(block);

		mm->avail -= drm_buddy_block_size(mm, block);

		list_add(&block->link, blocks);

	}



	block->parent = parent;

	return err;

}

EXPORT_SYMBOL(drm_buddy_block_trim);



/**

 * drm_buddy_alloc_blocks - allocate power-of-two blocks

 *

drivers/gpu/drm/i915/i915_ttm_buddy_manager.c

+10 −0
Original line number Diff line number Diff line
@@ -97,6 +97,16 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man, 
	if (unlikely(err))

		goto err_free_blocks;



	if (place->flags & TTM_PL_FLAG_CONTIGUOUS) {

		u64 original_size = (u64)bman_res->base.num_pages << PAGE_SHIFT;



		mutex_lock(&bman->lock);

		drm_buddy_block_trim(mm,

				     original_size,

				     &bman_res->blocks);

		mutex_unlock(&bman->lock);

	}



	*res = &bman_res->base;

	return 0;

include/drm/drm_buddy.h

+4 −0
Original line number Diff line number Diff line
@@ -140,6 +140,10 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm, 
			   struct list_head *blocks,

			   unsigned long flags);



int drm_buddy_block_trim(struct drm_buddy *mm,

			 u64 new_size,

			 struct list_head *blocks);



void drm_buddy_free_block(struct drm_buddy *mm, struct drm_buddy_block *block);



void drm_buddy_free_list(struct drm_buddy *mm, struct list_head *objects);