diff --git a/drivers/spi/spi_mpc83xx.c b/drivers/spi/spi_mpc83xx.c
index ff0b04895db0..e9798bf7b8c6 100644
--- a/drivers/spi/spi_mpc83xx.c
+++ b/drivers/spi/spi_mpc83xx.c
@@ -112,6 +112,8 @@ u32 mpc83xx_spi_tx_buf_##type(struct mpc83xx_spi *mpc83xx_spi)	\
 {								\
 	u32 data;						\
 	const type * tx = mpc83xx_spi->tx;			\
+	if (!tx)						\
+		return 0;					\
 	data = *tx++;						\
 	mpc83xx_spi->tx = tx;					\
 	return data;						\
diff --git a/drivers/spi/spi_s3c24xx.c b/drivers/spi/spi_s3c24xx.c
index 2ebe1fc4c398..8ca08713528e 100644
--- a/drivers/spi/spi_s3c24xx.c
+++ b/drivers/spi/spi_s3c24xx.c
@@ -174,7 +174,7 @@ static int s3c24xx_spi_setup(struct spi_device *spi)
 
 static inline unsigned int hw_txbyte(struct s3c24xx_spi *hw, int count)
 {
-	return hw->tx ? hw->tx[count] : 0xff;
+	return hw->tx ? hw->tx[count] : 0;
 }
 
 static int s3c24xx_spi_txrx(struct spi_device *spi, struct spi_transfer *t)
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index c8bb68099eb9..176f6e36dbfa 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -289,7 +289,7 @@ extern struct spi_master *spi_busnum_to_master(u16 busnum);
  * the data being transferred; that may reduce overhead, when the
  * underlying driver uses dma.
  *
- * If the transmit buffer is null, undefined data will be shifted out
+ * If the transmit buffer is null, zeroes will be shifted out
  * while filling rx_buf.  If the receive buffer is null, the data
  * shifted in will be discarded.  Only "len" bytes shift out (or in).
  * It's an error to try to shift out a partial word.  (For example, by