gpio: merrifield: Move hardware initialization to callback

The driver wants to initialize related registers before IRQ chip will be added.
That's why move it to a corresponding callback. It also fixes the NULL pointer
dereference.

Fixes: 8f86a5b ("gpio: merrifield: Pass irqchip when adding gpiochip")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-merrifield.c

@@ -362,8 +362,9 @@ static void mrfld_irq_handler(struct irq_desc *desc)
 	chained_irq_exit(irqchip, desc);
 }
 
-static void mrfld_irq_init_hw(struct mrfld_gpio *priv)
+static int mrfld_irq_init_hw(struct gpio_chip *chip)
 {
+	struct mrfld_gpio *priv = gpiochip_get_data(chip);
 	void __iomem *reg;
 	unsigned int base;
 
@@ -375,6 +376,8 @@ static void mrfld_irq_init_hw(struct mrfld_gpio *priv)
 		reg = gpio_reg(&priv->chip, base, GFER);
 		writel(0, reg);
 	}
+
+	return 0;
 }
 
 static const char *mrfld_gpio_get_pinctrl_dev_name(struct mrfld_gpio *priv)
@@ -447,6 +450,7 @@ static int mrfld_gpio_probe(struct pci_dev *pdev, const struct pci_device_id *id
 
 	girq = &priv->chip.irq;
 	girq->chip = &mrfld_irqchip;
+	girq->init_hw = mrfld_irq_init_hw;
 	girq->parent_handler = mrfld_irq_handler;
 	girq->num_parents = 1;
 	girq->parents = devm_kcalloc(&pdev->dev, girq->num_parents,
@@ -459,8 +463,6 @@ static int mrfld_gpio_probe(struct pci_dev *pdev, const struct pci_device_id *id
 	girq->default_type = IRQ_TYPE_NONE;
 	girq->handler = handle_bad_irq;
 
-	mrfld_irq_init_hw(priv);
-
 	pci_set_drvdata(pdev, priv);
 	retval = devm_gpiochip_add_data(&pdev->dev, &priv->chip, priv);
 	if (retval) {