gpio: Return EPROBE_DEFER if gc->to_irq is NULL

We are racing the registering of .to_irq when probing the
i2c driver. This results in random failure of touchscreen
devices.

Following errors could be seen in dmesg logs when gc->to_irq is NULL

[2.101857] i2c_hid i2c-FTS3528:00: HID over i2c has not been provided an Int IRQ
[2.101953] i2c_hid: probe of i2c-FTS3528:00 failed with error -22

To avoid this situation, defer probing until to_irq is registered.

This issue has been reported many times in past and people have been
using workarounds like changing the pinctrl_amd to built-in instead
of loading it as a module or by adding a softdep for pinctrl_amd into
the config file.

References :-
https://bugzilla.kernel.org/show_bug.cgi?id=209413
Syniurge/i2c-amd-mp2#3

Signed-off-by: Shreeya Patel <shreeya.patel@collabora.com>

drivers/gpio/gpiolib.c

@@ -3065,6 +3065,14 @@ int gpiod_to_irq(const struct gpio_desc *desc)
 
 		return retirq;
 	}
+	if (gc->irq.chip) {
+		/* avoid race condition with other code, which tries to lookup
+		 * an IRQ before the irqchip has been properly registered
+		 * (i.e. while gpiochip is still being brought up).
+		 */
+		return -EPROBE_DEFER;
+	}
+
 	return -ENXIO;
 }
 EXPORT_SYMBOL_GPL(gpiod_to_irq);