gpio: max77620: Initialize hardware state of interrupts

I noticed on Nexus 7 that after rebooting from downstream kernel to
upstream, the GPIO interrupt is triggering non-stop despite interrupts
being disabled for all of GPIOs. This happens because Nexus 7 uses a
soft-reboot, meaning that bootloader should take care of resetting
hardware, but the bootloader doesn't do it well. As a result, GPIO
interrupt may be left ON at a boot time. Let's mask all GPIO interrupts
at the driver's initialization time in order to resolve the issue.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Laxman Dewangan <ldewangan@nvidia.com>
Link: https://lore.kernel.org/r/20200709171203.12950-7-digetx@gmail.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-max77620.c

@@ -260,6 +260,30 @@ static int max77620_gpio_set_config(struct gpio_chip *gc, unsigned int offset,
 	return -ENOTSUPP;
 }
 
+static int max77620_gpio_irq_init_hw(struct gpio_chip *gc)
+{
+	struct max77620_gpio *gpio = gpiochip_get_data(gc);
+	unsigned int i;
+	int err;
+
+	/*
+	 * GPIO interrupts may be left ON after bootloader, hence let's
+	 * pre-initialize hardware to the expected state by disabling all
+	 * the interrupts.
+	 */
+	for (i = 0; i < MAX77620_GPIO_NR; i++) {
+		err = regmap_update_bits(gpio->rmap, GPIO_REG_ADDR(i),
+					 MAX77620_CNFG_GPIO_INT_MASK, 0);
+		if (err < 0) {
+			dev_err(gpio->dev,
+				"failed to disable interrupt: %d\n", err);
+			return err;
+		}
+	}
+
+	return 0;
+}
+
 static int max77620_gpio_probe(struct platform_device *pdev)
 {
 	struct max77620_chip *chip =  dev_get_drvdata(pdev->dev.parent);
@@ -295,6 +319,7 @@ static int max77620_gpio_probe(struct platform_device *pdev)
 	mgpio->gpio_chip.irq.chip = &max77620_gpio_irqchip;
 	mgpio->gpio_chip.irq.default_type = IRQ_TYPE_NONE;
 	mgpio->gpio_chip.irq.handler = handle_edge_irq;
+	mgpio->gpio_chip.irq.init_hw = max77620_gpio_irq_init_hw,
 	mgpio->gpio_chip.irq.threaded = true;
 
 	platform_set_drvdata(pdev, mgpio);