diff options
| author | Matthew Auld <matthew.auld@intel.com> | 2021-01-26 13:30:19 +0300 |
|---|---|---|
| committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2021-03-24 21:30:35 +0300 |
| commit | a29a22917d4cf14ad4e7a8c4c503629d5a771f06 (patch) | |
| tree | 12c4b8765b23abc8bf0e012620679d3ac2331c0f /drivers/gpu/drm/i915/i915_buddy.h | |
| parent | b3f0c15a8ef16ce402a2a51f98b43b485c2e0c6d (diff) | |
| download | linux-a29a22917d4cf14ad4e7a8c4c503629d5a771f06.tar.xz | |
drm/i915/buddy: document the unused header bits
The largest possible order is (63-PAGE_SHIFT), given that our min chunk
size is PAGE_SIZE. With that we should only need at most 6 bits to
represent all possible orders, giving us back 4 bits for other potential
uses. Include a simple selftest to verify this.
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20210126103019.177622-1-matthew.auld@intel.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Diffstat (limited to 'drivers/gpu/drm/i915/i915_buddy.h')
| -rw-r--r-- | drivers/gpu/drm/i915/i915_buddy.h | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/drivers/gpu/drm/i915/i915_buddy.h b/drivers/gpu/drm/i915/i915_buddy.h index ed41f3507cdc..9ce5200f4001 100644 --- a/drivers/gpu/drm/i915/i915_buddy.h +++ b/drivers/gpu/drm/i915/i915_buddy.h @@ -15,7 +15,9 @@ struct i915_buddy_block { #define I915_BUDDY_ALLOCATED (1 << 10) #define I915_BUDDY_FREE (2 << 10) #define I915_BUDDY_SPLIT (3 << 10) -#define I915_BUDDY_HEADER_ORDER GENMASK_ULL(9, 0) +/* Free to be used, if needed in the future */ +#define I915_BUDDY_HEADER_UNUSED GENMASK_ULL(9, 6) +#define I915_BUDDY_HEADER_ORDER GENMASK_ULL(5, 0) u64 header; struct i915_buddy_block *left; @@ -34,7 +36,8 @@ struct i915_buddy_block { struct list_head tmp_link; }; -#define I915_BUDDY_MAX_ORDER I915_BUDDY_HEADER_ORDER +/* Order-zero must be at least PAGE_SIZE */ +#define I915_BUDDY_MAX_ORDER (63 - PAGE_SHIFT) /* * Binary Buddy System. |