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@kontron.com>
Tested-by: Michael Brunner <michael.brunner@kontron.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/mfd/kempld-core.c b/drivers/mfd/kempld-core.c
index d3e2327..38917a8 100644 (file)
--- 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);