patches.renesas/0965-i2c-rcar-fix-MNR-interrupt-handling.patch

From 331fb731824c9a0b18238f0cbf98dc0daac640a3 Mon Sep 17 00:00:00 2001
From: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Date: Tue, 2 Sep 2014 01:15:26 +0400
Subject: i2c: rcar: fix MNR interrupt handling

Sometimes the MNR and MST interrupts happen simultaneously  (stop  automatically
follows NACK, according to the manuals) and in such case the ID_NACK flag  isn't
set since the MST interrupt handling precedes MNR and all interrupts are cleared
and disabled then, so that MNR interrupt is never noticed -- this causes NACK'ed
transfers to be falsely reported as successful. Exchanging MNR and  MST handlers
fixes this issue, however the MNR bit  somehow  gets set again even after  being
explicitly cleared, so I decided to completely suppress handling of all disabled
interrupts (which is a good thing anyway)...

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Cc: stable@vger.kernel.org
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
(cherry picked from commit dd318b0df27c582ac0d72a346fd6e693700be23c)
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
---
 drivers/i2c/busses/i2c-rcar.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index f3c7139dfa25..dc32f5fa75d0 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -367,18 +367,15 @@ static irqreturn_t rcar_i2c_irq(int irq, void *ptr)
 
 	msr = rcar_i2c_read(priv, ICMSR);
 
+	/* Only handle interrupts that are currently enabled */
+	msr &= rcar_i2c_read(priv, ICMIER);
+
 	/* Arbitration lost */
 	if (msr & MAL) {
 		rcar_i2c_flags_set(priv, (ID_DONE | ID_ARBLOST));
 		goto out;
 	}
 
-	/* Stop */
-	if (msr & MST) {
-		rcar_i2c_flags_set(priv, ID_DONE);
-		goto out;
-	}
-
 	/* Nack */
 	if (msr & MNR) {
 		/* go to stop phase */
@@ -388,6 +385,12 @@ static irqreturn_t rcar_i2c_irq(int irq, void *ptr)
 		goto out;
 	}
 
+	/* Stop */
+	if (msr & MST) {
+		rcar_i2c_flags_set(priv, ID_DONE);
+		goto out;
+	}
+
 	if (rcar_i2c_is_recv(priv))
 		rcar_i2c_flags_set(priv, rcar_i2c_irq_recv(priv, msr));
 	else
-- 
2.1.2