drivers: gpio: add interrupt support for the CH32V family

The WCH GPIO peripheral integrates with the EXTI and supports firing
interrupts when a GPIO pin changes.

Add optional support for firing a callback on rising edge, falling
edge, or both edges.

Tested on the `linkw` and the `ch32v006evt` using
`samples/basic/button`.

Signed-off-by: Michael Hope <michaelh@juju.nz>

drivers/gpio/Kconfig.wch_ch32v00x

@@ -5,3 +5,12 @@ config GPIO_WCH_GPIO
 	bool "WCH CH32V00x GPIO driver"
 	depends on DT_HAS_WCH_GPIO_ENABLED
 	default y
+
+config GPIO_WCH_GPIO_INTERRUPTS
+	bool "Interrupt support"
+	depends on GPIO_WCH_GPIO
+	depends on DT_HAS_WCH_EXTI_ENABLED
+	default y
+	help
+	  Support triggering an interrupt on pin change. Uses approximately
+	  700 bytes of flash and 60 bytes of RAM.

drivers/gpio/wch_gpio_ch32v00x.c

@@ -7,6 +7,7 @@
 #include <zephyr/drivers/clock_control.h>
 #include <zephyr/drivers/gpio.h>
 #include <zephyr/drivers/gpio/gpio_utils.h>
+#include <zephyr/drivers/interrupt_controller/wch_exti.h>
 #include <zephyr/dt-bindings/gpio/gpio.h>
 #include <zephyr/irq.h>
 
@@ -23,6 +24,7 @@ struct gpio_ch32v00x_config {
 
 struct gpio_ch32v00x_data {
 	struct gpio_driver_data common;
+	sys_slist_t callbacks;
 };
 
 static int gpio_ch32v00x_configure(const struct device *dev, gpio_pin_t pin, gpio_flags_t flags)
@@ -111,6 +113,131 @@ static int gpio_ch32v00x_port_toggle_bits(const struct device *dev, uint32_t pin
 	return 0;
 }
 
+#if defined(CONFIG_GPIO_WCH_GPIO_INTERRUPTS)
+
+static void gpio_ch32v00x_isr(uint8_t line, void *user)
+{
+	const struct device *dev = user;
+	struct gpio_ch32v00x_data *data = dev->data;
+
+	gpio_fire_callbacks(&data->callbacks, dev, BIT(line));
+}
+
+static int gpio_ch32v00x_configure_exti(const struct device *dev, gpio_pin_t pin)
+{
+	const struct gpio_ch32v00x_config *config = dev->config;
+	AFIO_TypeDef *afio = (AFIO_TypeDef *)DT_REG_ADDR(DT_NODELABEL(pinctrl));
+	uint8_t port_id;
+	uint8_t cr_id;
+	uint8_t bit0;
+
+	/* Convert the device into a port ID by checking the address */
+	switch ((uintptr_t)config->regs) {
+	case DT_REG_ADDR(DT_NODELABEL(gpioa)):
+		port_id = 0;
+		break;
+#if DT_NODE_EXISTS(DT_NODELABEL(gpiob))
+	case DT_REG_ADDR(DT_NODELABEL(gpiob)):
+		port_id = 1;
+		break;
+#endif
+	case DT_REG_ADDR(DT_NODELABEL(gpioc)):
+		port_id = 2;
+		break;
+	case DT_REG_ADDR(DT_NODELABEL(gpiod)):
+		port_id = 3;
+		break;
+#if DT_NODE_EXISTS(DT_NODELABEL(gpioe))
+	case DT_REG_ADDR(DT_NODELABEL(gpioe)):
+		port_id = 4;
+		break;
+#endif
+	default:
+		return -EINVAL;
+	}
+
+#if defined(AFIO_EXTICR_EXTI0)
+	/* CH32V003 style with one register with 2 bits per map. */
+	BUILD_ASSERT(AFIO_EXTICR_EXTI0 == 0x03);
+
+	(void)cr_id;
+	bit0 = pin << 1;
+	afio->EXTICR = (afio->EXTICR & ~(AFIO_EXTICR_EXTI0 << bit0)) | (port_id << bit0);
+#elif defined(AFIO_EXTICR1_EXTI0)
+	/*
+	 * CH32V20x style with multiple registers with 4 pins per register and 4 bits per
+	 * map.
+	 */
+	BUILD_ASSERT(AFIO_EXTICR1_EXTI0 == 0x0F);
+	BUILD_ASSERT(ARRAY_SIZE(afio->EXTICR) == 4);
+
+	cr_id = pin / 4;
+	bit0 = (pin % 4) * 4;
+	afio->EXTICR[cr_id] =
+		(afio->EXTICR[cr_id] & ~(AFIO_EXTICR1_EXTI0 << bit0)) | (port_id << bit0);
+#else
+#error Unrecognised EXTICR format
+#endif
+
+	return 0;
+}
+
+static int gpio_ch32v00x_pin_interrupt_configure(const struct device *dev, gpio_pin_t pin,
+						 enum gpio_int_mode mode,
+						 enum gpio_int_trig trigger)
+{
+	int err;
+
+	switch (mode) {
+	case GPIO_INT_MODE_DISABLED:
+		wch_exti_disable(pin);
+		err = wch_exti_configure(pin, NULL, NULL);
+		break;
+	case GPIO_INT_MODE_EDGE:
+		err = wch_exti_configure(pin, gpio_ch32v00x_isr, (void *)dev);
+		if (err != 0) {
+			break;
+		}
+
+		err = gpio_ch32v00x_configure_exti(dev, pin);
+		if (err != 0) {
+			break;
+		}
+
+		switch (trigger) {
+		case GPIO_INT_TRIG_LOW:
+			wch_exti_set_trigger(pin, WCH_EXTI_TRIGGER_FALLING_EDGE);
+			break;
+		case GPIO_INT_TRIG_HIGH:
+			wch_exti_set_trigger(pin, WCH_EXTI_TRIGGER_RISING_EDGE);
+			break;
+		case GPIO_INT_TRIG_BOTH:
+			wch_exti_set_trigger(pin, WCH_EXTI_TRIGGER_FALLING_EDGE |
+							  WCH_EXTI_TRIGGER_RISING_EDGE);
+			break;
+		default:
+			return -ENOTSUP;
+		}
+
+		wch_exti_enable(pin);
+		break;
+	default:
+		return -ENOTSUP;
+	}
+
+	return err;
+}
+
+static int gpio_ch32v00x_manage_callback(const struct device *dev, struct gpio_callback *callback,
+					 bool set)
+{
+	struct gpio_ch32v00x_data *data = dev->data;
+
+	return gpio_manage_callback(&data->callbacks, callback, set);
+}
+
+#endif /* CONFIG_GPIO_WCH_GPIO_INTERRUPTS */
+
 static DEVICE_API(gpio, gpio_ch32v00x_driver_api) = {
 	.pin_configure = gpio_ch32v00x_configure,
 	.port_get_raw = gpio_ch32v00x_port_get_raw,
@@ -118,6 +245,10 @@ static DEVICE_API(gpio, gpio_ch32v00x_driver_api) = {
 	.port_set_bits_raw = gpio_ch32v00x_port_set_bits_raw,
 	.port_clear_bits_raw = gpio_ch32v00x_port_clear_bits_raw,
 	.port_toggle_bits = gpio_ch32v00x_port_toggle_bits,
+#if defined(CONFIG_GPIO_WCH_GPIO_INTERRUPTS)
+	.pin_interrupt_configure = gpio_ch32v00x_pin_interrupt_configure,
+	.manage_callback = gpio_ch32v00x_manage_callback,
+#endif
 };
 
 static int gpio_ch32v00x_init(const struct device *dev)