pinctrl: sunxi: fix gpiochip_lock_as_irq() failure when pinmux is unknown

Fixes kernel hang during boot due to inability to set up IRQ on AXP313a.

The issue is caused by gpiochip_lock_as_irq() which is failing when gpio
is in uninitialized state.

Solution is to set pinmux to GPIO INPUT in
sunxi_pinctrl_irq_request_resources() if it wasn't initialized
earlier.

Tested on Orange Pi Zero 3.

Fixes: 01e10d0272b9 ("pinctrl: sunxi: Implement gpiochip::get_direction()")
Reviewed-by: Andre Przywara <[e-mail]>
Reviewed-by: Chen-Yu Tsai <[e-mail]>
Signed-off-by: Michal Piekos <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

drivers/pinctrl/sunxi/pinctrl-sunxi.c

···
 {
 	struct sunxi_pinctrl *pctl = irq_data_get_irq_chip_data(d);
 	struct sunxi_desc_function *func;
+	unsigned int offset;
+	u32 reg, shift, mask;
+	u8 disabled_mux, muxval;
 	int ret;
 
 	func = sunxi_pinctrl_desc_find_function_by_pin(pctl,
···
 	if (!func)
 		return -EINVAL;
 
-	ret = gpiochip_lock_as_irq(pctl->chip,
-			pctl->irq_array[d->hwirq] - pctl->desc->pin_base);
+	offset = pctl->irq_array[d->hwirq] - pctl->desc->pin_base;
+	sunxi_mux_reg(pctl, offset, &reg, &shift, &mask);
+	muxval = (readl(pctl->membase + reg) & mask) >> shift;
+
+	/* Change muxing to GPIO INPUT mode if at reset value */
+	if (pctl->flags & SUNXI_PINCTRL_NEW_REG_LAYOUT)
+		disabled_mux = SUN4I_FUNC_DISABLED_NEW;
+	else
+		disabled_mux = SUN4I_FUNC_DISABLED_OLD;
+
+	if (muxval == disabled_mux)
+		sunxi_pmx_set(pctl->pctl_dev, pctl->irq_array[d->hwirq],
+			      SUN4I_FUNC_INPUT);
+
+	ret = gpiochip_lock_as_irq(pctl->chip, offset);
 	if (ret) {
 		dev_err(pctl->dev, "unable to lock HW IRQ %lu for IRQ\n",
 			irqd_to_hwirq(d));

drivers/pinctrl/sunxi/pinctrl-sunxi.h

···
 
 #define SUN4I_FUNC_INPUT	0
 #define SUN4I_FUNC_IRQ		6
+#define SUN4I_FUNC_DISABLED_OLD 7
+#define SUN4I_FUNC_DISABLED_NEW 15
 
 #define SUNXI_PINCTRL_VARIANT_MASK	GENMASK(7, 0)
 #define SUNXI_PINCTRL_NEW_REG_LAYOUT	BIT(8)