linux-kernel - [PATCH 10/12] i2c: qup: send NACK for last read sub transfers

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Date:   Sat,  3 Feb 2018 13:28:15 +0530
From:   Abhishek Sahu <absahu@...eaurora.org>
To:     Andy Gross <andy.gross@...aro.org>,
        Wolfram Sang <wsa@...-dreams.de>
Cc:     David Brown <david.brown@...aro.org>,
        Sricharan R <sricharan@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        Abhishek Sahu <absahu@...eaurora.org>
Subject: [PATCH 10/12] i2c: qup: send NACK for last read sub transfers

According to I2c specification, “If a master-receiver sends a
repeated START condition, it sends a not-acknowledge (A) just
before the repeated START condition”. QUP v2 supports sending
of NACK without stop with QUP_TAG_V2_DATARD_NACK so added the
same.

Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
---
 drivers/i2c/busses/i2c-qup.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-qup.c b/drivers/i2c/busses/i2c-qup.c
index ba717bb..edea3b9 100644
--- a/drivers/i2c/busses/i2c-qup.c
+++ b/drivers/i2c/busses/i2c-qup.c
@@ -113,6 +113,7 @@
 #define QUP_TAG_V2_DATAWR              0x82
 #define QUP_TAG_V2_DATAWR_STOP         0x83
 #define QUP_TAG_V2_DATARD              0x85
+#define QUP_TAG_V2_DATARD_NACK         0x86
 #define QUP_TAG_V2_DATARD_STOP         0x87
 
 /* Status, Error flags */
@@ -609,7 +610,9 @@ static int qup_i2c_set_tags(u8 *tags, struct qup_i2c_dev *qup,
 			tags[len++] = QUP_TAG_V2_DATAWR_STOP;
 	} else {
 		if (msg->flags & I2C_M_RD)
-			tags[len++] = QUP_TAG_V2_DATARD;
+			tags[len++] = qup->blk.pos == (qup->blk.count - 1) ?
+				      QUP_TAG_V2_DATARD_NACK :
+				      QUP_TAG_V2_DATARD;
 		else
 			tags[len++] = QUP_TAG_V2_DATAWR;
 	}
-- 
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