gpio/langwell: Clear edge bit before handling

I don't have the specs for this beast, but it looks a lot like the PXA
GPIO block. Though I bet it's the same IP and the driver should have
reused the PXA code.

Acknowleding the edge detect status after handling one or more gpio
interrupts looks wrong. We might lose an edge which came in while we
handled the previous one.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Alek Du <alek.du@intel.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/gpio/langwell_gpio.c

@@ -190,23 +190,22 @@ static void lnw_irq_handler(unsigned irq, struct irq_desc *desc)
 	struct irq_data *data = irq_desc_get_irq_data(desc);
 	struct lnw_gpio *lnw = irq_data_get_irq_handler_data(data);
 	struct irq_chip *chip = irq_data_get_irq_chip(data);
-	u32 base, gpio, gedr_v;
+	u32 base, gpio, mask;
 	unsigned long pending;
 	void __iomem *gedr;
 
 	/* check GPIO controller to check which pin triggered the interrupt */
 	for (base = 0; base < lnw->chip.ngpio; base += 32) {
 		gedr = gpio_reg(&lnw->chip, base, GEDR);
-		gedr_v = pending = readl(gedr);
-		if (!gedr_v)
-			continue;
+		pending = readl(gedr);
 		while (pending) {
 			gpio = __ffs(pending) - 1;
-			pending &= ~BIT(gpio);
+			mask = BIT(gpio);
+			pending &= ~mask;
+			/* Clear before handling so we can't lose an edge */
+			writel(mask, gedr);
 			generic_handle_irq(lnw->irq_base + base + gpio);
 		}
-		/* clear the edge detect status bit */
-		writel(gedr_v, gedr);
 	}
 
 	chip->irq_eoi(data);