[PATCH] mfd: kempld-core: Fix potential hang-up during boot

[Guenter Roeck <linux@roeck-us.net>]

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@kontron.com>
Tested-by: Michael Brunner <michael.brunner@kontron.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 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 d3e2327..38917a8 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);
 
-- 
1.7.9.7