pinctrl: apple: Always return valid type in apple_gpio_irq_type

apple_gpio_irq_type can possibly return -EINVAL which triggers the
following compile error with gcc 9 because the type no longer fits
into the mask.

  drivers/pinctrl/pinctrl-apple-gpio.c: In function 'apple_gpio_irq_set_type':
  ././include/linux/compiler_types.h:335:38: error: call to '__compiletime_assert_289' declared with attribute error: FIELD_PREP: value too large for the field
    335 |  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
        |                                      ^
  [...]
  drivers/pinctrl/pinctrl-apple-gpio.c:294:7: note: in expansion of macro 'FIELD_PREP'
    294 |       FIELD_PREP(REG_GPIOx_MODE, irqtype));
        |       ^~~~~~~~~~

Fix this by making the return value always valid and instead checking
for REG_GPIOx_IN_IRQ_OFF in apple_gpio_irq_set_type and return -EINVAL
from there.

Fixes: a0f160f ("pinctrl: add pinctrl/GPIO driver for Apple SoCs")
Signed-off-by: Sven Peter <sven@svenpeter.dev>
Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Link: https://lore.kernel.org/r/20211101150640.46553-1-sven@svenpeter.dev
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Author: svenpeter42

drivers/pinctrl/pinctrl-apple-gpio.c

@@ -258,7 +258,7 @@ static void apple_gpio_irq_ack(struct irq_data *data)
 	       pctl->base + REG_IRQ(irqgrp, data->hwirq));
 }
 
-static int apple_gpio_irq_type(unsigned int type)
+static unsigned int apple_gpio_irq_type(unsigned int type)
 {
 	switch (type & IRQ_TYPE_SENSE_MASK) {
 	case IRQ_TYPE_EDGE_RISING:
@@ -272,7 +272,7 @@ static int apple_gpio_irq_type(unsigned int type)
 	case IRQ_TYPE_LEVEL_LOW:
 		return REG_GPIOx_IN_IRQ_LO;
 	default:
-		return -EINVAL;
+		return REG_GPIOx_IN_IRQ_OFF;
 	}
 }
 
@@ -288,7 +288,7 @@ static void apple_gpio_irq_unmask(struct irq_data *data)
 {
 	struct apple_gpio_pinctrl *pctl =
 		gpiochip_get_data(irq_data_get_irq_chip_data(data));
-	int irqtype = apple_gpio_irq_type(irqd_get_trigger_type(data));
+	unsigned int irqtype = apple_gpio_irq_type(irqd_get_trigger_type(data));
 
 	apple_gpio_set_reg(pctl, data->hwirq, REG_GPIOx_MODE,
 			   FIELD_PREP(REG_GPIOx_MODE, irqtype));
@@ -313,10 +313,10 @@ static int apple_gpio_irq_set_type(struct irq_data *data,
 {
 	struct apple_gpio_pinctrl *pctl =
 		gpiochip_get_data(irq_data_get_irq_chip_data(data));
-	int irqtype = apple_gpio_irq_type(type);
+	unsigned int irqtype = apple_gpio_irq_type(type);
 
-	if (irqtype < 0)
-		return irqtype;
+	if (irqtype == REG_GPIOx_IN_IRQ_OFF)
+		return -EINVAL;
 
 	apple_gpio_set_reg(pctl, data->hwirq, REG_GPIOx_MODE,
 			   FIELD_PREP(REG_GPIOx_MODE, irqtype));