diff --git a/drivers/edac/amd64_edac.c b/drivers/edac/amd64_edac.c
index 475235c402e8..0c0d11c72925 100644
--- a/drivers/edac/amd64_edac.c
+++ b/drivers/edac/amd64_edac.c
@@ -2796,13 +2796,13 @@ static inline void decode_bus_error(int node_id, struct mce *m)
  * the instance_id. For example, instance_id=0xYXXXXX where Y is the channel
  * number.
  *
- * For DRAM ECC errors, the Chip Select number is given in bits [2:0] of
+ * For DRAM ECC errors, the Chip Select number is given in bits [1:0] of
  * the MCA_SYND[ErrorInformation] field.
  */
 static void umc_get_err_info(struct mce *m, struct err_info *err)
 {
 	err->channel = (m->ipid & GENMASK(31, 0)) >> 20;
-	err->csrow = m->synd & 0x7;
+	err->csrow = m->synd & 0x3;
 }
 
 static void decode_umc_error(int node_id, struct mce *m)