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

Matthew Auld <matthew.auld@xxxxxxxxx> · Wed, 10 Jul 2024 13:50:22 +0100

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?


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@xxxxxxx> 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>
Series is:
Acked-by: Alex Deucher <alexander.deucher@xxxxxxx>

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








