Re: [PATCH] drm/buddy: Add start address support to trim function

["Paneer Selvam, Arunpravin" <arunpravin.paneerselvam@amd.com>]

Hi Matthew,

On 7/10/2024 6:20 PM, Matthew Auld wrote:
> On 10/07/2024 07:03, Paneer Selvam, Arunpravin wrote:
>> Thanks Alex.
>>
>> Hi Matthew,
>> Any comments?
>
> Do we not pass the required address alignment when allocating the 
> pages in the first place?
If address alignment is really useful, we can add that in the 
drm_buddy_alloc_blocks() function.

Thanks,
Arun.
>
>>
>> Thanks,
>> Arun.
>>
>> On 7/9/2024 1:42 AM, Alex Deucher wrote:
>>> On Thu, Jul 4, 2024 at 4:40 AM Arunpravin Paneer Selvam
>>> <Arunpravin.PaneerSelvam@amd.com> 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@amd.com>
>>> Series is:
>>> Acked-by: Alex Deucher <alexander.deucher@amd.com>
>>>
>>> I'd like to take this series through the amdgpu tree if there are no
>>> objections as it's required for display buffers on some chips and I'd
>>> like to make sure it lands in 6.11.
>>>
>>> Thanks,
>>>
>>> Alex
>>>
>>>> ---
>>>>   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 94f8c34fc293..8cebe1fa4e9d 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 82570f77e817..0c2f735f0265 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);
>>>>
>>>> -- 
>>>> 2.25.1
>>>>
>>