The reason is that our DCC requires 768K alignment in some cases. I haven't read this patch series, but one way to do that is to align to 256K, overallocate by 512K, and then not use either 0, 256K, or 512K at the beginning to get to 768K alignment.
Marek
On Tue, Jul 23, 2024, 11:04 Matthew Auld <matthew.auld@xxxxxxxxx> wrote:
On 23/07/2024 14:43, Paneer Selvam, Arunpravin wrote:
> Hi Matthew,
>
> Can we push this version for now as we need to mainline the DCC changes
> ASAP,
> while we continue our discussion and proceed to implement the permanent
> solution
> for address alignment?
Yeah, we can always merge now and circle back around later, if this for
sure helps your usecase and is needed asap. I just didn't fully get the
idea for needing this interface, but likely I am missing something.
>
> Thanks,
> Arun.
>
> On 7/23/2024 6:55 PM, Arunpravin Paneer Selvam wrote:
>> - Add a new start parameter in trim function to specify exact
>> address from where to start the trimming. This would help us
>> in situations like if drivers would like to do address alignment
>> for specific requirements.
>>
>> - Add a new flag DRM_BUDDY_TRIM_DISABLE. Drivers can use this
>> flag to disable the allocator trimming part. This patch enables
>> the drivers control trimming and they can do it themselves
>> based on the application requirements.
>>
>> v1:(Matthew)
>> - check new_start alignment with min chunk_size
>> - use range_overflows()
>>
>> Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@xxxxxxx>
>> Acked-by: Alex Deucher <alexander.deucher@xxxxxxx>
>> Acked-by: Christian König <christian.koenig@xxxxxxx>
>> ---
>> drivers/gpu/drm/drm_buddy.c | 25 +++++++++++++++++++++++--
>> drivers/gpu/drm/xe/xe_ttm_vram_mgr.c | 2 +-
>> include/drm/drm_buddy.h | 2 ++
>> 3 files changed, 26 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
>> index 6a8e45e9d0ec..103c185bb1c8 100644
>> --- a/drivers/gpu/drm/drm_buddy.c
>> +++ b/drivers/gpu/drm/drm_buddy.c
>> @@ -851,6 +851,7 @@ static int __alloc_contig_try_harder(struct
>> drm_buddy *mm,
>> * drm_buddy_block_trim - free unused pages
>> *
>> * @mm: DRM buddy manager
>> + * @start: start address to begin the trimming.
>> * @new_size: original size requested
>> * @blocks: Input and output list of allocated blocks.
>> * MUST contain single block as input to be trimmed.
>> @@ -866,11 +867,13 @@ static int __alloc_contig_try_harder(struct
>> drm_buddy *mm,
>> * 0 on success, error code on failure.
>> */
>> int drm_buddy_block_trim(struct drm_buddy *mm,
>> + u64 *start,
>> u64 new_size,
>> struct list_head *blocks)
>> {
>> struct drm_buddy_block *parent;
>> struct drm_buddy_block *block;
>> + u64 block_start, block_end;
>> LIST_HEAD(dfs);
>> u64 new_start;
>> int err;
>> @@ -882,6 +885,9 @@ int drm_buddy_block_trim(struct drm_buddy *mm,
>> struct drm_buddy_block,
>> link);
>> + block_start = drm_buddy_block_offset(block);
>> + block_end = block_start + drm_buddy_block_size(mm, block);
>> +
>> if (WARN_ON(!drm_buddy_block_is_allocated(block)))
>> return -EINVAL;
>> @@ -894,6 +900,20 @@ int drm_buddy_block_trim(struct drm_buddy *mm,
>> if (new_size == drm_buddy_block_size(mm, block))
>> return 0;
>> + new_start = block_start;
>> + if (start) {
>> + new_start = *start;
>> +
>> + if (new_start < block_start)
>> + return -EINVAL;
>> +
>> + if (!IS_ALIGNED(new_start, mm->chunk_size))
>> + return -EINVAL;
>> +
>> + if (range_overflows(new_start, new_size, block_end))
>> + return -EINVAL;
>> + }
>> +
>> list_del(&block->link);
>> mark_free(mm, block);
>> mm->avail += drm_buddy_block_size(mm, block);
>> @@ -904,7 +924,6 @@ int drm_buddy_block_trim(struct drm_buddy *mm,
>> 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, NULL);
>> if (err) {
>> @@ -1066,7 +1085,8 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm,
>> } while (1);
>> /* Trim the allocated block to the required size */
>> - if (original_size != size) {
>> + if (!(flags & DRM_BUDDY_TRIM_DISABLE) &&
>> + original_size != size) {
>> struct list_head *trim_list;
>> LIST_HEAD(temp);
>> u64 trim_size;
>> @@ -1083,6 +1103,7 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm,
>> }
>> drm_buddy_block_trim(mm,
>> + NULL,
>> trim_size,
>> trim_list);
>> diff --git a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
>> b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
>> index fe3779fdba2c..423b261ea743 100644
>> --- a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
>> +++ b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
>> @@ -150,7 +150,7 @@ static int xe_ttm_vram_mgr_new(struct
>> ttm_resource_manager *man,
>> } while (remaining_size);
>> if (place->flags & TTM_PL_FLAG_CONTIGUOUS) {
>> - if (!drm_buddy_block_trim(mm, vres->base.size, &vres->blocks))
>> + if (!drm_buddy_block_trim(mm, NULL, vres->base.size,
>> &vres->blocks))
>> size = vres->base.size;
>> }
>> diff --git a/include/drm/drm_buddy.h b/include/drm/drm_buddy.h
>> index 2a74fa9d0ce5..9689a7c5dd36 100644
>> --- a/include/drm/drm_buddy.h
>> +++ b/include/drm/drm_buddy.h
>> @@ -27,6 +27,7 @@
>> #define DRM_BUDDY_CONTIGUOUS_ALLOCATION BIT(2)
>> #define DRM_BUDDY_CLEAR_ALLOCATION BIT(3)
>> #define DRM_BUDDY_CLEARED BIT(4)
>> +#define DRM_BUDDY_TRIM_DISABLE BIT(5)
>> struct drm_buddy_block {
>> #define DRM_BUDDY_HEADER_OFFSET GENMASK_ULL(63, 12)
>> @@ -155,6 +156,7 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm,
>> unsigned long flags);
>> int drm_buddy_block_trim(struct drm_buddy *mm,
>> + u64 *start,
>> u64 new_size,
>> struct list_head *blocks);
>>
>> base-commit: b27d70e1042bf6a31ba7e5acf58b61c9cd28f95b
>
