spi: nuc900: Fix setting multiple bits settings in register

The correct way to set multiple bits settings is always clear these
bit fields before set new settings.

Current code does not cause problem because the reset value of these
bit fields are 0, and these settings only set once during probe.
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

drivers/spi/spi-nuc900.c

@@ -38,7 +38,9 @@
 /* usi register bit */
 #define ENINT		(0x01 << 17)
 #define ENFLG		(0x01 << 16)
+#define SLEEP		(0x0f << 12)
 #define TXNUM		(0x03 << 8)
+#define TXBITLEN	(0x1f << 3)
 #define TXNEG		(0x01 << 2)
 #define RXNEG		(0x01 << 1)
 #define LSB		(0x01 << 10)
@@ -116,19 +118,16 @@ static void nuc900_spi_chipsel(struct spi_device *spi, int value)
 	}
 }
 
-static void nuc900_spi_setup_txnum(struct nuc900_spi *hw,
-							unsigned int txnum)
+static void nuc900_spi_setup_txnum(struct nuc900_spi *hw, unsigned int txnum)
 {
 	unsigned int val;
 	unsigned long flags;
 
 	spin_lock_irqsave(&hw->lock, flags);
 
-	val = __raw_readl(hw->regs + USI_CNT);
+	val = __raw_readl(hw->regs + USI_CNT) & ~TXNUM;
 
-	if (!txnum)
-		val &= ~TXNUM;
-	else
+	if (txnum)
 		val |= txnum << 0x08;
 
 	__raw_writel(val, hw->regs + USI_CNT);
@@ -145,7 +144,7 @@ static void nuc900_spi_setup_txbitlen(struct nuc900_spi *hw,
 
 	spin_lock_irqsave(&hw->lock, flags);
 
-	val = __raw_readl(hw->regs + USI_CNT);
+	val = __raw_readl(hw->regs + USI_CNT) & ~TXBITLEN;
 
 	val |= (txbitlen << 0x03);
 
@@ -284,12 +283,11 @@ static void nuc900_set_sleep(struct nuc900_spi *hw, unsigned int sleep)
 
 	spin_lock_irqsave(&hw->lock, flags);
 
-	val = __raw_readl(hw->regs + USI_CNT);
+	val = __raw_readl(hw->regs + USI_CNT) & ~SLEEP;
 
 	if (sleep)
 		val |= (sleep << 12);
-	else
-		val &= ~(0x0f << 12);
+
 	__raw_writel(val, hw->regs + USI_CNT);
 
 	spin_unlock_irqrestore(&hw->lock, flags);