[3.11.y.z extended stable] Patch "mfd: kempld-core: Fix potential hang-up during boot" has been added to staging queue

[Luis Henriques]

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

    mfd: kempld-core: Fix potential hang-up during boot

to the linux-3.11.y-queue branch of the 3.11.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-3.11.y-queue

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

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 8f3e5855bfa1145893052465cc0c23ce40c2bb03 Mon Sep 17 00:00:00 2001
From: Guenter Roeck <linux at roeck-us.net>
Date: Thu, 20 Mar 2014 08:12:28 -0700
Subject: mfd: kempld-core: Fix potential hang-up during boot

commit 204747c970c0d568721c76ab8a57dde0e5dcf0d5 upstream.

On PXT and COMe-cPC2 boards it is observed that the hardware
mutex is acquired but not being released during initialization.
This can result in a hang-up during boot if the driver is built
into the kernel.

Releasing the mutex twice if it was acquired fixes the problem.
Subsequent request/release cycles work as expected, so the fix is
only needed during initialization.

Reviewed-by: Michael Brunner <michael.brunner at kontron.com>
Tested-by: Michael Brunner <michael.brunner at kontron.com>
Signed-off-by: Guenter Roeck <linux at roeck-us.net>
Signed-off-by: Lee Jones <lee.jones at linaro.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/mfd/kempld-core.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/mfd/kempld-core.c b/drivers/mfd/kempld-core.c
index 686a456..1b1b462 100644
--- a/drivers/mfd/kempld-core.c
+++ b/drivers/mfd/kempld-core.c
@@ -322,9 +322,12 @@ static int kempld_detect_device(struct kempld_device_data *pld)
 		return -ENODEV;
 	}

-	/* Release hardware mutex if aquired */
-	if (!(index_reg & KEMPLD_MUTEX_KEY))
+	/* Release hardware mutex if acquired */
+	if (!(index_reg & KEMPLD_MUTEX_KEY)) {
 		iowrite8(KEMPLD_MUTEX_KEY, pld->io_index);
+		/* PXT and COMe-cPC2 boards may require a second release */
+		iowrite8(KEMPLD_MUTEX_KEY, pld->io_index);
+	}

 	mutex_unlock(&pld->lock);

--
1.9.1