diff --git a/drivers/mtd/nand/pxa3xx_nand.c b/drivers/mtd/nand/pxa3xx_nand.c
index 6ea520a..32cb4d1 100644
--- a/drivers/mtd/nand/pxa3xx_nand.c
+++ b/drivers/mtd/nand/pxa3xx_nand.c
@@ -316,7 +316,7 @@ static struct pxa3xx_nand_flash *builtin_flash_types[] = {
 #define tAR_NDTR1(r)	(((r) >> 0) & 0xf)
 
 /* convert nano-seconds to nand flash controller clock cycles */
-#define ns2cycle(ns, clk)	(int)(((ns) * (clk / 1000000) / 1000) - 1)
+#define ns2cycle(ns, clk)	(int)(DIV_ROUND_UP((ns) * (clk / 1000000), 1000) - 1)
 
 /* convert nand flash controller clock cycles to nano-seconds */
 #define cycle2ns(c, clk)	((((c) + 1) * 1000000 + clk / 500) / (clk / 1000))