1 files changed, 19 insertions, 5 deletions

diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index d3e06a5e981e..d87a17a819d0 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -1085,13 +1085,27 @@ void debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
         ref.dev = dev;
         ref.dev_addr = dma_addr;
         bucket = get_hash_bucket(&ref, &flags);
-        entry = bucket_find_exact(bucket, &ref);
 
-        if (!entry)
-                goto out;
+        list_for_each_entry(entry, &bucket->list, list) {
+                if (!exact_match(&ref, entry))
+                        continue;
+
+                /*
+                 * The same physical address can be mapped multiple
+                 * times. Without a hardware IOMMU this results in the
+                 * same device addresses being put into the dma-debug
+                 * hash multiple times too. This can result in false
+                 * positives being reported. Therefore we implement a
+                 * best-fit algorithm here which updates the first entry
+                 * from the hash which fits the reference value and is
+                 * not currently listed as being checked.
+                 */
+                if (entry->map_err_type == MAP_ERR_NOT_CHECKED) {
+                        entry->map_err_type = MAP_ERR_CHECKED;
+                        break;
+                }
+        }
 
-        entry->map_err_type = MAP_ERR_CHECKED;
-out:
         put_hash_bucket(bucket, &flags);
 }
 EXPORT_SYMBOL(debug_dma_mapping_error);