[PATCH AUTOSEL 4.9 14/23] i2c: uniphier-f: issue STOP only for last message or I2C_M_STOP

From: Sasha Levin <Alexander.Levin@microsoft.com>
To: "stable@vger.kernel.org" <stable@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>,
	Wolfram Sang <wsa@the-dreams.de>,
	Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL 4.9 14/23] i2c: uniphier-f: issue STOP only for last message or I2C_M_STOP
Date: Mon, 24 Sep 2018 14:49:31 +0000	[thread overview]
Message-ID: <20180924144919.164617-14-alexander.levin@microsoft.com> (raw)
In-Reply-To: <20180924144919.164617-1-alexander.levin@microsoft.com>

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

[ Upstream commit 4c85609b08c4761eca0a40fd7beb06bc650f252d ]

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: 6a62974b667f ("i2c: uniphier_f: add UniPhier FIFO-builtin 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>
---
 drivers/i2c/busses/i2c-uniphier-f.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/i2c/busses/i2c-uniphier-f.c b/drivers/i2c/busses/i2c-uniphier-f.c
index db9105e52c79..0da4991dd356 100644
--- a/drivers/i2c/busses/i2c-uniphier-f.c
+++ b/drivers/i2c/busses/i2c-uniphier-f.c
@@ -400,11 +400,8 @@ static int uniphier_fi2c_master_xfer(struct i2c_adapter *adap,
 		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_fi2c_master_xfer_one(adap, msg, stop);
 		if (ret)
-- 
2.17.1
