[RFC PATCH V7 2/9] drm/gpu: Add gpu_buddy_addr_to_block helper

[Tejas Upadhyay <tejas.upadhyay@intel.com>]

Add helper with primary purpose is to efficiently trace a specific
physical memory address back to its corresponding TTM buffer object.

Signed-off-by: Tejas Upadhyay <tejas.upadhyay@intel.com>
---
 drivers/gpu/buddy.c       | 56 +++++++++++++++++++++++++++++++++++++++
 include/linux/gpu_buddy.h |  2 ++
 2 files changed, 58 insertions(+)

diff --git a/drivers/gpu/buddy.c b/drivers/gpu/buddy.c
index 52686672e99f..2d26c2a0f971 100644
--- a/drivers/gpu/buddy.c
+++ b/drivers/gpu/buddy.c
@@ -589,6 +589,62 @@ void gpu_buddy_free_block(struct gpu_buddy *mm,
 }
 EXPORT_SYMBOL(gpu_buddy_free_block);
 
+/**
+ * gpu_buddy_addr_to_block - given physical address find a block
+ *
+ * @mm: GPU buddy manager
+ * @addr: Physical address
+ *
+ * Returns:
+ * gpu_buddy_block on success, NULL or error code on failure
+ */
+struct gpu_buddy_block *gpu_buddy_addr_to_block(struct gpu_buddy *mm, u64 addr)
+{
+	struct gpu_buddy_block *block;
+	LIST_HEAD(dfs);
+	u64 end;
+	int i;
+
+	end = addr + SZ_4K - 1;
+	for (i = 0; i < mm->n_roots; ++i)
+		list_add_tail(&mm->roots[i]->tmp_link, &dfs);
+
+	do {
+		u64 block_start;
+		u64 block_end;
+
+		block = list_first_entry_or_null(&dfs,
+						 struct gpu_buddy_block,
+						 tmp_link);
+		if (!block)
+			break;
+
+		list_del(&block->tmp_link);
+
+		block_start = gpu_buddy_block_offset(block);
+		block_end = block_start + gpu_buddy_block_size(mm, block) - 1;
+
+		if (!overlaps(addr, end, block_start, block_end))
+			continue;
+
+		if (contains(addr, end, block_start, block_end) &&
+		    !gpu_buddy_block_is_split(block)) {
+			if (gpu_buddy_block_is_free(block))
+				return NULL;
+			else if (gpu_buddy_block_is_allocated(block) && !mm->clear_avail)
+				return block;
+		}
+
+		if (gpu_buddy_block_is_split(block)) {
+			list_add(&block->right->tmp_link, &dfs);
+			list_add(&block->left->tmp_link, &dfs);
+		}
+	} while (1);
+
+	return ERR_PTR(-ENXIO);
+}
+EXPORT_SYMBOL(gpu_buddy_addr_to_block);
+
 static void __gpu_buddy_free_list(struct gpu_buddy *mm,
 				  struct list_head *objects,
 				  bool mark_clear,
diff --git a/include/linux/gpu_buddy.h b/include/linux/gpu_buddy.h
index 5fa917ba5450..957c69c560bc 100644
--- a/include/linux/gpu_buddy.h
+++ b/include/linux/gpu_buddy.h
@@ -231,6 +231,8 @@ void gpu_buddy_reset_clear(struct gpu_buddy *mm, bool is_clear);
 
 void gpu_buddy_free_block(struct gpu_buddy *mm, struct gpu_buddy_block *block);
 
+struct gpu_buddy_block *gpu_buddy_addr_to_block(struct gpu_buddy *mm, u64 addr);
+
 void gpu_buddy_free_list(struct gpu_buddy *mm,
 			 struct list_head *objects,
 			 unsigned int flags);
-- 
2.52.0