gpio: davinci: use chained_irq_enter/chained_irq_exit API

It's unsafe to call IRQ chip callbacks (.irq_mask/irq_unmask/irq_ack)
from chained IRQ handler directly. Because, Davinci GPIO block is used
by different SoCs, which, in turn, have different Main IRQ controllers
(Davinci - aintc, cp-intc; Keystone - arm-gic) which may introduce
diffrent set of IRQ chip callbacks. As result, call of
gpio_irq_handler() on Keysone will simply cause crash the system,
because ARM-GIC implements .irq_eoi() instead of .irq_ack().

Hence, fix it by using Kernel chained_irq_enter/chained_irq_exit APIs as
they are intended to handle exact such cases.
Signed-off-by: NGrygorii Strashko <grygorii.strashko@ti.com>
Acked-by: NLinus Walleij <linus.walleij@linaro.org>
Acked-by: NSantosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: NSekhar Nori <nsekhar@ti.com>

drivers/gpio/gpio-davinci.c

@@ -22,6 +22,7 @@
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/platform_data/gpio-davinci.h>
+#include <linux/irqchip/chained_irq.h>
 
 struct davinci_gpio_regs {
 	u32	dir;
@@ -321,8 +322,7 @@ gpio_irq_handler(unsigned irq, struct irq_desc *desc)
 		mask <<= 16;
 
 	/* temporarily mask (level sensitive) parent IRQ */
-	desc->irq_data.chip->irq_mask(&desc->irq_data);
-	desc->irq_data.chip->irq_ack(&desc->irq_data);
+	chained_irq_enter(irq_desc_get_chip(desc), desc);
 	while (1) {
 		u32		status;
 		int		bit;
@@ -343,7 +343,7 @@ gpio_irq_handler(unsigned irq, struct irq_desc *desc)
 						 d->chip.base + bit));
 		}
 	}
-	desc->irq_data.chip->irq_unmask(&desc->irq_data);
+	chained_irq_exit(irq_desc_get_chip(desc), desc);
 	/* now it may re-trigger */
 }