--- a/drivers/mtd/nand/davinci_nand.c
+++ b/drivers/mtd/nand/davinci_nand.c
@@ -350,13 +350,16 @@ compare:
 
 	/*
 	 * Clear any previous address calculation by doing a dummy read of an
-	 * error address register.
+	 * error address register.  UNDOCUMENTED that the ECC engine won't
+	 * recover after 5-bit ECC errors without this step.
 	 */
 	davinci_nand_readl(info, NAND_ERR_ADD1_OFFSET);
 
 	/* Start address calculation, and wait for it to complete.
 	 * We _could_ start reading more data while this is working,
-	 * to speed up the overall page read.
+	 * to speed up the overall page read.  UNDOCUMENTED that
+	 * reading some ERRVAL register is needed in all cases, not
+	 * just when an error must be corrected.
 	 */
 	davinci_nand_writel(info, NANDFCR_OFFSET,
 			davinci_nand_readl(info, NANDFCR_OFFSET) | BIT(13));