linux-kernel - [PATCH 3.11 085/182] mfd: kempld-core: Fix potential hang-up during boot

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Message-Id: <1398329507-5911-86-git-send-email-luis.henriques@canonical.com>
Date:	Thu, 24 Apr 2014 09:50:10 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Guenter Roeck <linux@...ck-us.net>,
	Lee Jones <lee.jones@...aro.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.11 085/182] mfd: kempld-core: Fix potential hang-up during boot

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

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

From: Guenter Roeck <linux@...ck-us.net>

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@...tron.com>
Tested-by: Michael Brunner <michael.brunner@...tron.com>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
Signed-off-by: Lee Jones <lee.jones@...aro.org>
Signed-off-by: Luis Henriques <luis.henriques@...onical.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

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