[ARM] pxa: make pxa_gpio_irq_type() processor generic

The main issue here is that pxa3xx does not have GAFRx registers,
access directly to these registers should be avoided for pxa3xx:

1. introduce __gpio_is_occupied() to indicate the GAFRx and GPDRx
   registers are already configured on pxa{25x,27x} while returns
   0 always on pxa3xx

2. pxa_gpio_mode(gpio | GPIO_IN) is replaced directly with assign-
   ment of GPDRx, the side effect of this change is that the pin
   _must_ be configured before use, pxa_gpio_irq_type() will not
   change the pin to GPIO, as this restriction is sane, esp. with
   the new MFP framework
Signed-off-by: eric miao <eric.miao@marvell.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mach-pxa/gpio.c

@@ -164,6 +164,20 @@ static long GPIO_IRQ_rising_edge[4];
 static long GPIO_IRQ_falling_edge[4];
 static long GPIO_IRQ_mask[4];
 
+/*
+ * On PXA25x and PXA27x, GAFRx and GPDRx together decide the alternate
+ * function of a GPIO, and GPDRx cannot be altered once configured. It
+ * is attributed as "occupied" here (I know this terminology isn't
+ * accurate, you are welcome to propose a better one :-)
+ */
+static int __gpio_is_occupied(unsigned gpio)
+{
+	if (cpu_is_pxa25x() || cpu_is_pxa27x())
+		return GAFR(gpio) & (0x3 << (((gpio) & 0xf) * 2));
+	else
+		return 0;
+}
+
 static int pxa_gpio_irq_type(unsigned int irq, unsigned int type)
 {
 	int gpio, idx;
@@ -179,12 +193,14 @@ static int pxa_gpio_irq_type(unsigned int irq, unsigned int type)
 		     GPIO_IRQ_falling_edge[idx] |
 		     GPDR(gpio)) & GPIO_bit(gpio))
 			return 0;
-		if (GAFR(gpio) & (0x3 << (((gpio) & 0xf)*2)))
+
+		if (__gpio_is_occupied(gpio))
 			return 0;
+
 		type = IRQ_TYPE_EDGE_RISING | IRQ_TYPE_EDGE_FALLING;
 	}
 
-	pxa_gpio_mode(gpio | GPIO_IN);
+	GPDR(gpio) &= ~GPIO_bit(gpio);
 
 	if (type & IRQ_TYPE_EDGE_RISING)
 		__set_bit(gpio, GPIO_IRQ_rising_edge);