[ 3.5.y.z extended stable ] Patch "i2c: xiic: must always write 16-bit words to TX_FIFO" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    i2c: xiic: must always write 16-bit words to TX_FIFO

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From a371255c82d65bca8c041bdc8634433be2690d4d Mon Sep 17 00:00:00 2001
From: "Steven A. Falco" <sfalco at harris.com>
Date: Mon, 22 Apr 2013 09:34:39 +0000
Subject: [PATCH] i2c: xiic: must always write 16-bit words to TX_FIFO

commit c39e8e4354ce4daf23336de5daa28a3b01f00aa6 upstream.

The TX_FIFO register is 10 bits wide.  The lower 8 bits are the data to be
written, while the upper two bits are flags to indicate stop/start.

The driver apparently attempted to optimize write access, by only writing a
byte in those cases where the stop/start bits are zero.  However, we have
seen cases where the lower byte is duplicated onto the upper byte by the
hardware, which causes inadvertent stop/starts.

This patch changes the write access to the transmit FIFO to always be 16 bits
wide.

Signed off by: Steven A. Falco <sfalco at harris.com>
Signed-off-by: Wolfram Sang <wsa at the-dreams.de>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/i2c/busses/i2c-xiic.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c
index 641d0e5..15d20de 100644
--- a/drivers/i2c/busses/i2c-xiic.c
+++ b/drivers/i2c/busses/i2c-xiic.c
@@ -312,10 +312,8 @@ static void xiic_fill_tx_fifo(struct xiic_i2c *i2c)
 			/* last message in transfer -> STOP */
 			data |= XIIC_TX_DYN_STOP_MASK;
 			dev_dbg(i2c->adap.dev.parent, "%s TX STOP\n", __func__);
-
-			xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET, data);
-		} else
-			xiic_setreg8(i2c, XIIC_DTR_REG_OFFSET, data);
+		}
+		xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET, data);
 	}
 }

--
1.8.1.2