diff --git a/drivers/char/tpm/tpm_tis.c b/drivers/char/tpm/tpm_tis.c
index 7e55aa9ce680..ebd0e75a3e4d 100644
--- a/drivers/char/tpm/tpm_tis.c
+++ b/drivers/char/tpm/tpm_tis.c
@@ -223,7 +223,7 @@ static int tpm_tcg_read_bytes(struct tpm_tis_data *data, u32 addr, u16 len,
 }
 
 static int tpm_tcg_write_bytes(struct tpm_tis_data *data, u32 addr, u16 len,
-			       u8 *value)
+			       const u8 *value)
 {
 	struct tpm_tis_tcg_phy *phy = to_tpm_tis_tcg_phy(data);
 
diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 1e957e923d21..fdde971bc810 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -252,7 +252,7 @@ static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
  * tpm.c can skip polling for the data to be available as the interrupt is
  * waited for here
  */
-static int tpm_tis_send_data(struct tpm_chip *chip, u8 *buf, size_t len)
+static int tpm_tis_send_data(struct tpm_chip *chip, const u8 *buf, size_t len)
 {
 	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
 	int rc, status, burstcnt;
@@ -343,7 +343,7 @@ static void disable_interrupts(struct tpm_chip *chip)
  * tpm.c can skip polling for the data to be available as the interrupt is
  * waited for here
  */
-static int tpm_tis_send_main(struct tpm_chip *chip, u8 *buf, size_t len)
+static int tpm_tis_send_main(struct tpm_chip *chip, const u8 *buf, size_t len)
 {
 	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
 	int rc;
diff --git a/drivers/char/tpm/tpm_tis_core.h b/drivers/char/tpm/tpm_tis_core.h
index e2212f021a02..6bbac319ff3b 100644
--- a/drivers/char/tpm/tpm_tis_core.h
+++ b/drivers/char/tpm/tpm_tis_core.h
@@ -98,7 +98,7 @@ struct tpm_tis_phy_ops {
 	int (*read_bytes)(struct tpm_tis_data *data, u32 addr, u16 len,
 			  u8 *result);
 	int (*write_bytes)(struct tpm_tis_data *data, u32 addr, u16 len,
-			   u8 *value);
+			   const u8 *value);
 	int (*read16)(struct tpm_tis_data *data, u32 addr, u16 *result);
 	int (*read32)(struct tpm_tis_data *data, u32 addr, u32 *result);
 	int (*write32)(struct tpm_tis_data *data, u32 addr, u32 src);
@@ -128,7 +128,7 @@ static inline int tpm_tis_read32(struct tpm_tis_data *data, u32 addr,
 }
 
 static inline int tpm_tis_write_bytes(struct tpm_tis_data *data, u32 addr,
-				      u16 len, u8 *value)
+				      u16 len, const u8 *value)
 {
 	return data->phy_ops->write_bytes(data, addr, len, value);
 }
diff --git a/drivers/char/tpm/tpm_tis_spi.c b/drivers/char/tpm/tpm_tis_spi.c
index 88fe72ae967f..e49f5b9b739a 100644
--- a/drivers/char/tpm/tpm_tis_spi.c
+++ b/drivers/char/tpm/tpm_tis_spi.c
@@ -57,7 +57,7 @@ static inline struct tpm_tis_spi_phy *to_tpm_tis_spi_phy(struct tpm_tis_data *da
 }
 
 static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
-				u8 *buffer, u8 direction)
+				u8 *in, const u8 *out)
 {
 	struct tpm_tis_spi_phy *phy = to_tpm_tis_spi_phy(data);
 	int ret = 0;
@@ -71,7 +71,7 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
 	while (len) {
 		transfer_len = min_t(u16, len, MAX_SPI_FRAMESIZE);
 
-		phy->tx_buf[0] = direction | (transfer_len - 1);
+		phy->tx_buf[0] = (in ? 0x80 : 0) | (transfer_len - 1);
 		phy->tx_buf[1] = 0xd4;
 		phy->tx_buf[2] = addr >> 8;
 		phy->tx_buf[3] = addr;
@@ -112,14 +112,8 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
 		spi_xfer.cs_change = 0;
 		spi_xfer.len = transfer_len;
 		spi_xfer.delay_usecs = 5;
-
-		if (direction) {
-			spi_xfer.tx_buf = NULL;
-			spi_xfer.rx_buf = buffer;
-		} else {
-			spi_xfer.tx_buf = buffer;
-			spi_xfer.rx_buf = NULL;
-		}
+		spi_xfer.tx_buf = out;
+		spi_xfer.rx_buf = in;
 
 		spi_message_init(&m);
 		spi_message_add_tail(&spi_xfer, &m);
@@ -128,7 +122,10 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
 			goto exit;
 
 		len -= transfer_len;
-		buffer += transfer_len;
+		if (in)
+			in += transfer_len;
+		if (out)
+			out += transfer_len;
 	}
 
 exit:
@@ -139,13 +136,13 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
 static int tpm_tis_spi_read_bytes(struct tpm_tis_data *data, u32 addr,
 				  u16 len, u8 *result)
 {
-	return tpm_tis_spi_transfer(data, addr, len, result, 0x80);
+	return tpm_tis_spi_transfer(data, addr, len, result, NULL);
 }
 
 static int tpm_tis_spi_write_bytes(struct tpm_tis_data *data, u32 addr,
-				   u16 len, u8 *value)
+				   u16 len, const u8 *value)
 {
-	return tpm_tis_spi_transfer(data, addr, len, value, 0);
+	return tpm_tis_spi_transfer(data, addr, len, NULL, value);
 }
 
 static int tpm_tis_spi_read16(struct tpm_tis_data *data, u32 addr, u16 *result)
