drm/xe/vram: drop 2G block restriction

Currently we limit the max block size for all users to ensure each block
can fit within a sg entry (uint). Drop this restriction and tweak the sg
construction to instead handle this itself and break down blocks which
are too big, if needed. Most users don't need an sg list in the first
place.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Satyanarayana K V P <satyanarayana.k.v.p@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Tested-by: Satyanarayana K V P <satyanarayana.k.v.p@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241113172346.256165-2-matthew.auld@intel.com

drivers/gpu/drm/xe/xe_ttm_vram_mgr.c

@@ -52,7 +52,7 @@ static int xe_ttm_vram_mgr_new(struct ttm_resource_manager *man,
 	struct xe_ttm_vram_mgr *mgr = to_xe_ttm_vram_mgr(man);
 	struct xe_ttm_vram_mgr_resource *vres;
 	struct drm_buddy *mm = &mgr->mm;
-	u64 size, remaining_size, min_page_size;
+	u64 size, min_page_size;
 	unsigned long lpfn;
 	int err;
 
@@ -98,27 +98,15 @@ static int xe_ttm_vram_mgr_new(struct ttm_resource_manager *man,
 		goto error_fini;
 	}
 
-	if (WARN_ON(min_page_size > SZ_2G)) { /* FIXME: sg limit */
-		err = -EINVAL;
-		goto error_fini;
-	}
-
-	if (WARN_ON((size > SZ_2G &&
-		     (vres->base.placement & TTM_PL_FLAG_CONTIGUOUS)))) {
-		err = -EINVAL;
-		goto error_fini;
-	}
-
 	if (WARN_ON(!IS_ALIGNED(size, min_page_size))) {
 		err = -EINVAL;
 		goto error_fini;
 	}
 
 	mutex_lock(&mgr->lock);
 	if (lpfn <= mgr->visible_size >> PAGE_SHIFT && size > mgr->visible_avail) {
-		mutex_unlock(&mgr->lock);
 		err = -ENOSPC;
-		goto error_fini;
+		goto error_unlock;
 	}
 
 	if (place->fpfn + (size >> PAGE_SHIFT) != place->lpfn &&
@@ -129,25 +117,11 @@ static int xe_ttm_vram_mgr_new(struct ttm_resource_manager *man,
 		lpfn = max_t(unsigned long, place->fpfn + (size >> PAGE_SHIFT), lpfn);
 	}
 
-	remaining_size = size;
-	do {
-		/*
-		 * Limit maximum size to 2GiB due to SG table limitations.
-		 * FIXME: Should maybe be handled as part of sg construction.
-		 */
-		u64 alloc_size = min_t(u64, remaining_size, SZ_2G);
-
-		err = drm_buddy_alloc_blocks(mm, (u64)place->fpfn << PAGE_SHIFT,
-					     (u64)lpfn << PAGE_SHIFT,
-					     alloc_size,
-					     min_page_size,
-					     &vres->blocks,
-					     vres->flags);
-		if (err)
-			goto error_free_blocks;
-
-		remaining_size -= alloc_size;
-	} while (remaining_size);
+	err = drm_buddy_alloc_blocks(mm, (u64)place->fpfn << PAGE_SHIFT,
+				     (u64)lpfn << PAGE_SHIFT, size,
+				     min_page_size, &vres->blocks, vres->flags);
+	if (err)
+		goto error_unlock;
 
 	if (place->flags & TTM_PL_FLAG_CONTIGUOUS) {
 		if (!drm_buddy_block_trim(mm, NULL, vres->base.size, &vres->blocks))
@@ -194,9 +168,7 @@ static int xe_ttm_vram_mgr_new(struct ttm_resource_manager *man,
 
 	*res = &vres->base;
 	return 0;
-
-error_free_blocks:
-	drm_buddy_free_list(mm, &vres->blocks, 0);
+error_unlock:
 	mutex_unlock(&mgr->lock);
 error_fini:
 	ttm_resource_fini(man, &vres->base);
@@ -393,7 +365,8 @@ int xe_ttm_vram_mgr_alloc_sgt(struct xe_device *xe,
 	xe_res_first(res, offset, length, &cursor);
 	while (cursor.remaining) {
 		num_entries++;
-		xe_res_next(&cursor, cursor.size);
+		/* Limit maximum size to 2GiB due to SG table limitations. */
+		xe_res_next(&cursor, min_t(u64, cursor.size, SZ_2G));
 	}
 
 	r = sg_alloc_table(*sgt, num_entries, GFP_KERNEL);
@@ -413,7 +386,7 @@ int xe_ttm_vram_mgr_alloc_sgt(struct xe_device *xe,
 	xe_res_first(res, offset, length, &cursor);
 	for_each_sgtable_sg((*sgt), sg, i) {
 		phys_addr_t phys = cursor.start + tile->mem.vram.io_start;
-		size_t size = cursor.size;
+		size_t size = min_t(u64, cursor.size, SZ_2G);
 		dma_addr_t addr;
 
 		addr = dma_map_resource(dev, phys, size, dir,
@@ -426,7 +399,7 @@ int xe_ttm_vram_mgr_alloc_sgt(struct xe_device *xe,
 		sg_dma_address(sg) = addr;
 		sg_dma_len(sg) = size;
 
-		xe_res_next(&cursor, cursor.size);
+		xe_res_next(&cursor, size);
 	}
 
 	return 0;