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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Wolfram Sang <wsa@the-dreams.de>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.18 053/168] i2c: uniphier: issue STOP only for last message or I2C_M_STOP
Date:   Mon,  8 Oct 2018 20:30:33 +0200
Message-Id: <20181008175622.064836780@linuxfoundation.org>
In-Reply-To: <20181008175620.043587728@linuxfoundation.org>
References: <20181008175620.043587728@linuxfoundation.org>
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4.18-stable review patch.  If anyone has any objections, please let me know.

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

From: Masahiro Yamada <yamada.masahiro@socionext.com>

[ Upstream commit 38f5d8d8cbb2ffa2b54315118185332329ec891c ]

This driver currently emits a STOP if the next message is not
I2C_MD_RD.  It should not do it because it disturbs the I2C_RDWR
ioctl, where read/write transactions are combined without STOP
between.

Issue STOP only when the message is the last one _or_ flagged with
I2C_M_STOP.

Fixes: dd6fd4a32793 ("i2c: uniphier: add UniPhier FIFO-less I2C driver")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/i2c/busses/i2c-uniphier.c |    7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

--- a/drivers/i2c/busses/i2c-uniphier.c
+++ b/drivers/i2c/busses/i2c-uniphier.c
@@ -248,11 +248,8 @@ static int uniphier_i2c_master_xfer(stru
 		return ret;
 
 	for (msg = msgs; msg < emsg; msg++) {
-		/* If next message is read, skip the stop condition */
-		bool stop = !(msg + 1 < emsg && msg[1].flags & I2C_M_RD);
-		/* but, force it if I2C_M_STOP is set */
-		if (msg->flags & I2C_M_STOP)
-			stop = true;
+		/* Emit STOP if it is the last message or I2C_M_STOP is set. */
+		bool stop = (msg + 1 == emsg) || (msg->flags & I2C_M_STOP);
 
 		ret = uniphier_i2c_master_xfer_one(adap, msg, stop);
 		if (ret)