mxc: emulate GPIO interrupt on both-edges

MXC GPIO controller does not support generation of interrupts on both
edges. Emulate this mode in software by reconfiguring the irq trigger
polarity on each interrupt. This follows an example of
drivers/mfd/asic3.c.
Signed-off-by: Guennadi Liakhovetski <lg@denx.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

arch/arm/plat-mxc/gpio.c

@@ -64,6 +64,8 @@ static void gpio_unmask_irq(u32 irq)
 	_set_gpio_irqenable(&mxc_gpio_ports[gpio / 32], gpio & 0x1f, 1);
 }
 
+static int mxc_gpio_get(struct gpio_chip *chip, unsigned offset);
+
 static int gpio_set_irq_type(u32 irq, u32 type)
 {
 	u32 gpio = irq_to_gpio(irq);
@@ -72,6 +74,7 @@ static int gpio_set_irq_type(u32 irq, u32 type)
 	int edge;
 	void __iomem *reg = port->base;
 
+	port->both_edges &= ~(1 << (gpio & 31));
 	switch (type) {
 	case IRQ_TYPE_EDGE_RISING:
 		edge = GPIO_INT_RISE_EDGE;
@@ -79,13 +82,24 @@ static int gpio_set_irq_type(u32 irq, u32 type)
 	case IRQ_TYPE_EDGE_FALLING:
 		edge = GPIO_INT_FALL_EDGE;
 		break;
+	case IRQ_TYPE_EDGE_BOTH:
+		val = mxc_gpio_get(&port->chip, gpio & 31);
+		if (val) {
+			edge = GPIO_INT_LOW_LEV;
+			pr_debug("mxc: set GPIO %d to low trigger\n", gpio);
+		} else {
+			edge = GPIO_INT_HIGH_LEV;
+			pr_debug("mxc: set GPIO %d to high trigger\n", gpio);
+		}
+		port->both_edges |= 1 << (gpio & 31);
+		break;
 	case IRQ_TYPE_LEVEL_LOW:
 		edge = GPIO_INT_LOW_LEV;
 		break;
 	case IRQ_TYPE_LEVEL_HIGH:
 		edge = GPIO_INT_HIGH_LEV;
 		break;
-	default:	/* this includes IRQ_TYPE_EDGE_BOTH */
+	default:
 		return -EINVAL;
 	}
 
@@ -98,6 +112,34 @@ static int gpio_set_irq_type(u32 irq, u32 type)
 	return 0;
 }
 
+static void mxc_flip_edge(struct mxc_gpio_port *port, u32 gpio)
+{
+	void __iomem *reg = port->base;
+	u32 bit, val;
+	int edge;
+
+	reg += GPIO_ICR1 + ((gpio & 0x10) >> 2); /* lower or upper register */
+	bit = gpio & 0xf;
+	val = __raw_readl(reg);
+	edge = (val >> (bit << 1)) & 3;
+	val &= ~(0x3 << (bit << 1));
+	switch (edge) {
+	case GPIO_INT_HIGH_LEV:
+		edge = GPIO_INT_LOW_LEV;
+		pr_debug("mxc: switch GPIO %d to low trigger\n", gpio);
+		break;
+	case GPIO_INT_LOW_LEV:
+		edge = GPIO_INT_HIGH_LEV;
+		pr_debug("mxc: switch GPIO %d to high trigger\n", gpio);
+		break;
+	default:
+		pr_err("mxc: invalid configuration for GPIO %d: %x\n",
+		       gpio, edge);
+		return;
+	}
+	__raw_writel(val | (edge << (bit << 1)), reg);
+}
+
 /* handle n interrupts in one status register */
 static void mxc_gpio_irq_handler(struct mxc_gpio_port *port, u32 irq_stat)
 {
@@ -105,11 +147,16 @@ static void mxc_gpio_irq_handler(struct mxc_gpio_port *port, u32 irq_stat)
 
 	gpio_irq_no = port->virtual_irq_start;
 	for (; irq_stat != 0; irq_stat >>= 1, gpio_irq_no++) {
+		u32 gpio = irq_to_gpio(gpio_irq_no);
 
 		if ((irq_stat & 1) == 0)
 			continue;
 
 		BUG_ON(!(irq_desc[gpio_irq_no].handle_irq));
+
+		if (port->both_edges & (1 << (gpio & 31)))
+			mxc_flip_edge(port, gpio);
+
 		irq_desc[gpio_irq_no].handle_irq(gpio_irq_no,
 				&irq_desc[gpio_irq_no]);
 	}

arch/arm/plat-mxc/include/mach/gpio.h

@@ -35,6 +35,7 @@ struct mxc_gpio_port {
 	int irq;
 	int virtual_irq_start;
 	struct gpio_chip chip;
+	u32 both_edges;
 };
 
 int mxc_gpio_init(struct mxc_gpio_port*, int);