linux-kernel - [ 21/46] i2c: xiic: must always write 16-bit words to TX

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Message-Id: <20130506225822.882768175@linuxfoundation.org>
Date:	Mon,  6 May 2013 15:58:27 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Wolfram Sang <wsa@...-dreams.de>
Subject: [ 21/46] i2c: xiic: must always write 16-bit words to TX_FIFO

3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: "Steven A. Falco" <sfalco@...ris.com>

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@...ris.com>
Signed-off-by: Wolfram Sang <wsa@...-dreams.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/i2c/busses/i2c-xiic.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

--- a/drivers/i2c/busses/i2c-xiic.c
+++ b/drivers/i2c/busses/i2c-xiic.c
@@ -311,10 +311,8 @@ static void xiic_fill_tx_fifo(struct xii
 			/* 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);
 	}
 }

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