diff --git a/drivers/mtd/nand/pxa3xx_nand.c b/drivers/mtd/nand/pxa3xx_nand.c
index 7582581aefe3..cc55cbc2b308 100644
--- a/drivers/mtd/nand/pxa3xx_nand.c
+++ b/drivers/mtd/nand/pxa3xx_nand.c
@@ -298,7 +298,7 @@ static struct pxa3xx_nand_flash *builtin_flash_types[] = {
 #define NDTR1_tAR(c)	(min((c), 15) << 0)
 
 /* convert nano-seconds to nand flash controller clock cycles */
-#define ns2cycle(ns, clk)	(int)(((ns) * (clk / 1000000) / 1000) + 1)
+#define ns2cycle(ns, clk)	(int)(((ns) * (clk / 1000000) / 1000) - 1)
 
 static void pxa3xx_nand_set_timing(struct pxa3xx_nand_info *info,
 				   const struct pxa3xx_nand_timing *t)