diff --git a/arch/arm/include/asm/arch-kirkwood/spi.h b/arch/arm/include/asm/arch-kirkwood/spi.h
index c79bed7..113f258 100644
--- a/arch/arm/include/asm/arch-kirkwood/spi.h
+++ b/arch/arm/include/asm/arch-kirkwood/spi.h
@@ -49,6 +49,7 @@
 #define MISO_MPP11	(1 << 2)
 
 #define KWSPI_CLKPRESCL_MASK	0x1f
+#define KWSPI_CLKPRESCL_MIN	0x12
 #define KWSPI_CSN_ACT		1 /* Activates serial memory interface */
 #define KWSPI_SMEMRDY		(1 << 1) /* SerMem Data xfer ready */
 #define KWSPI_IRQUNMASK		1 /* unmask SPI interrupt */
diff --git a/drivers/spi/kirkwood_spi.c b/drivers/spi/kirkwood_spi.c
index f4523a3..a7cda75 100644
--- a/drivers/spi/kirkwood_spi.c
+++ b/drivers/spi/kirkwood_spi.c
@@ -56,8 +56,9 @@
 	writel(~KWSPI_CSN_ACT | KWSPI_SMEMRDY, &spireg->ctrl);
 
 	/* calculate spi clock prescaller using max_hz */
-	data = ((CONFIG_SYS_TCLK / 2) / max_hz) & KWSPI_CLKPRESCL_MASK;
-	data |= 0x10;
+	data = ((CONFIG_SYS_TCLK / 2) / max_hz) + 0x10;
+	data = data < KWSPI_CLKPRESCL_MIN ? KWSPI_CLKPRESCL_MIN : data;
+	data = data > KWSPI_CLKPRESCL_MASK ? KWSPI_CLKPRESCL_MASK : data;
 
 	/* program spi clock prescaller using max_hz */
 	writel(KWSPI_ADRLEN_3BYTE | data, &spireg->cfg);