drm/buddy: Add start address support to trim function

- 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>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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);
 

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;
 	}
 

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);