linux-kernel - [PATCH 4.4 21/37] i2c: rcar: dont issue stop when HW does it automatically

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Date:   Tue,  5 Jun 2018 19:01:26 +0200
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+renesas@...g-engineering.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        Fabrizio Castro <fabrizio.castro@...renesas.com>,
        Biju Das <biju.das@...renesas.com>
Subject: [PATCH 4.4 21/37] i2c: rcar: dont issue stop when HW does it automatically

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

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

From: Wolfram Sang <wsa+renesas@...g-engineering.com>

commit d89667b14f9d13b684287f6189ca209af5feee43 upstream.

The manual says (55.4.8.6) that HW does automatically send STOP after
NACK was received. My measuerments confirm that.

Signed-off-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
Signed-off-by: Wolfram Sang <wsa@...-dreams.de>
Signed-off-by: Fabrizio Castro <fabrizio.castro@...renesas.com>
Reviewed-by: Biju Das <biju.das@...renesas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -455,8 +455,8 @@ static irqreturn_t rcar_i2c_irq(int irq,
 
 	/* Nack */
 	if (msr & MNR) {
-		/* go to stop phase */
-		rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_STOP);
+		/* HW automatically sends STOP after received NACK */
+		rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_DATA);
 		rcar_i2c_write(priv, ICMIER, RCAR_IRQ_STOP);
 		rcar_i2c_flags_set(priv, ID_NACK);
 		goto out;