[PATCH] i2c: mvtwsi: Swab the register address if its size is > 1

[Stefan Roese]

Testing on Armada XP with an EEPROM using register address with size
of 2 has shown, that the register address bytes are sent to the I2C
EEPROM in the incorrect order. This patch swabs the address bytes so
that the correct address is transferred to the I2C device.

BTW: This worked without any issues before migrating Armada XP to
DM I2C.

Signed-off-by: Stefan Roese <sr at denx.de>
Cc: Heiko Schocher <hs at denx.de>
Cc: Samuel Holland <samuel at sholland.org>
Cc: Baruch Siach <baruch at tkos.co.il>
Cc: Pali Rohár <pali at kernel.org>
Cc: Marek Behún <marek.behun at nic.cz>
---
It would be good if other users of this I2C driver could test this change
with e.g. I2C EEPROM devices using 2 bytes (or more) for addressing.

 drivers/i2c/mvtwsi.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/mvtwsi.c b/drivers/i2c/mvtwsi.c
index 236bfb8d8e7f..ff21e3c52b58 100644
--- a/drivers/i2c/mvtwsi.c
+++ b/drivers/i2c/mvtwsi.c
@@ -860,6 +860,9 @@ static int mvtwsi_i2c_xfer(struct udevice *bus, struct i2c_msg *msg, int nmsgs)
 {
 	struct mvtwsi_i2c_dev *dev = dev_get_priv(bus);
 	struct i2c_msg *dmsg, *omsg, dummy;
+	u8 *addr_buf_ptr;
+	u8 addr_buf[4];
+	int i;
 
 	memset(&dummy, 0, sizeof(struct i2c_msg));
 
@@ -873,12 +876,17 @@ static int mvtwsi_i2c_xfer(struct udevice *bus, struct i2c_msg *msg, int nmsgs)
 	omsg = nmsgs == 1 ? &dummy : msg;
 	dmsg = nmsgs == 1 ? msg : msg + 1;
 
+	/* We need to swap the register address if its size is > 1 */
+	addr_buf_ptr = &addr_buf[0];
+	for (i = omsg->len; i > 0; i--)
+		*addr_buf_ptr++ = omsg->buf[i - 1];
+
 	if (dmsg->flags & I2C_M_RD)
-		return __twsi_i2c_read(dev->base, dmsg->addr, omsg->buf,
+		return __twsi_i2c_read(dev->base, dmsg->addr, addr_buf,
 				       omsg->len, dmsg->buf, dmsg->len,
 				       dev->tick);
 	else
-		return __twsi_i2c_write(dev->base, dmsg->addr, omsg->buf,
+		return __twsi_i2c_write(dev->base, dmsg->addr, addr_buf,
 					omsg->len, dmsg->buf, dmsg->len,
 					dev->tick);
 }
-- 
2.34.0