Blackfin arch: reset POLAR setting when acquiring a gpio for the first time

when requesting a GPIO for the first time, the POLAR setting is not
set to a sane state.  this can lead to indeterminate behavior that
cannot be resolved without an explicit write to the Blackfin port POLAR
register.

when requesting a GPIO for the first time via gpio_request(), the POLAR
setting for the GPIO in question should be set to sane state.  this
should occur if the GPIO has not been allocated in any other way.

some examples:
 - when doing something like "request_irq(); gpio_request();" on the
   same GPIO, the POLAR setting should not be reset.
 - when doing "gpio_request(); gpio_request();" on the same GPIO, the
   POLAR setting should be reset only the first time and not the second.
Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>

arch/blackfin/kernel/bfin_gpio.c

@@ -1053,9 +1053,15 @@ int bfin_gpio_request(unsigned gpio, const char *label)
 		local_irq_restore_hw(flags);
 		return -EBUSY;
 	}
-	if (unlikely(reserved_gpio_irq_map[gpio_bank(gpio)] & gpio_bit(gpio)))
+	if (unlikely(reserved_gpio_irq_map[gpio_bank(gpio)] & gpio_bit(gpio))) {
 		printk(KERN_NOTICE "bfin-gpio: GPIO %d is already reserved as gpio-irq!"
 		       " (Documentation/blackfin/bfin-gpio-notes.txt)\n", gpio);
+	}
+#ifndef BF548_FAMILY
+	else {	/* Reset POLAR setting when acquiring a gpio for the first time */
+		set_gpio_polar(gpio, 0);
+	}
+#endif
 
 	reserved_gpio_map[gpio_bank(gpio)] |= gpio_bit(gpio);
 	set_label(gpio, label);