[3.13.y.z extended stable] Patch "i2c: rcar: fix MNR interrupt handling" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    i2c: rcar: fix MNR interrupt handling

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.8.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 27d1ba1a2083fe64b0aa2482a72a1539d5f34b95 Mon Sep 17 00:00:00 2001
From: Sergei Shtylyov <sergei.shtylyov at cogentembedded.com>
Date: Tue, 2 Sep 2014 01:15:26 +0400
Subject: i2c: rcar: fix MNR interrupt handling

commit dd318b0df27c582ac0d72a346fd6e693700be23c upstream.

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 at cogentembedded.com>
Signed-off-by: Wolfram Sang <wsa at the-dreams.de>
[ kamal: backport to 3.13-stable: context ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/i2c/busses/i2c-rcar.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index 56de337..e64bb5b 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -488,6 +488,9 @@ static irqreturn_t rcar_i2c_irq(int irq, void *ptr)

 	msr = rcar_i2c_status_get(priv);

+	/* Only handle interrupts that are currently enabled */
+	msr &= rcar_i2c_read(priv, ICMIER);
+
 	/*
 	 * Arbitration lost
 	 */
@@ -503,15 +506,6 @@ static irqreturn_t rcar_i2c_irq(int irq, void *ptr)
 	}

 	/*
-	 * Stop
-	 */
-	if (msr & MST) {
-		dev_dbg(dev, "Stop\n");
-		rcar_i2c_flags_set(priv, ID_DONE);
-		goto out;
-	}
-
-	/*
 	 * Nack
 	 */
 	if (msr & MNR) {
@@ -524,6 +518,12 @@ 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;
+	}
+
 	/*
 	 * recv/send
 	 */
--
1.9.1