core: pinmux: improve dynamic pinmux configuration at runtime

cores/arduino/SerialUSB.h

@@ -41,10 +41,6 @@ class SerialUSB_ : public ZephyrSerial {
 	uint32_t baudrate;
 	static void baudChangeHandler(const struct device *dev, uint32_t rate);
 
-	void _reinit_if_needed() override {
-		/* prevent reinit: USB device is always available */
-	}
-
 private:
 	bool started = false;
 

cores/arduino/zephyrCommon.cpp

@@ -1,3 +1,3 @@
 /*
  * Copyright (c) 2022 Dhruva Gole
  *
@@ -6,20 +6,152 @@
 
 #include <Arduino.h>
 #include "zephyrInternal.h"
+#include <zephyr/drivers/pinctrl.h>
 
 #include <zephyr/spinlock.h>
 
-// create an array of arduino_pins with functions to reinitialize pins if needed
-static const struct device *pinmux_array[DT_PROP_LEN(DT_PATH(zephyr_user), digital_pin_gpios)] = {
-	nullptr};
+#if defined(ARDUINO)
+/*
+ * The global ARDUINO macro is numeric (e.g. 10607) in Arduino builds.
+ * Temporarily hide it so pinctrl token concatenation can use the literal
+ * custom state name "ARDUINO" from devicetree pinctrl-names.
+ * Otherwise, the generated pinctrl state identifiers would be like PINCTRL_STATE_10607 instead of
+ * PINCTRL_STATE_ARDUINO.
+ */
+#pragma push_macro("ARDUINO")
+#undef ARDUINO
+#endif
+
+/*
+ * Pinctrl configuration structures for dynamic pin switching.
+ *
+ * Map deferred-init peripherals with their pinctrl configuration from devicetree.
+ */
+#define PINCTRL_NODE_DEFERRED(node_id) DT_PROP(node_id, zephyr_deferred_init)
+
+#define PINCTRL_DECLARE_IF_DEFERRED(node_id)                                                       \
+	COND_CODE_1(PINCTRL_NODE_DEFERRED(node_id), (PINCTRL_DT_DEV_CONFIG_DECLARE(node_id);), ())
+
+DT_FOREACH_STATUS_OKAY_NODE(PINCTRL_DECLARE_IF_DEFERRED)
+
+#if DT_HAS_ALIAS(arduino_log_uart)
+PINCTRL_DT_DEV_CONFIG_DECLARE(DT_ALIAS(arduino_log_uart));
+#endif
+
+struct pinctrl_map_entry {
+	const struct device *dev;
+	const struct pinctrl_dev_config *pcfg;
+};
+
+#define PINCTRL_MAP_ENTRY(node_id) {DEVICE_DT_GET(node_id), PINCTRL_DT_DEV_CONFIG_GET(node_id)},
+#define PINCTRL_MAP_ENTRY_IF_PRESENT(node_id)                                                      \
+	COND_CODE_1(PINCTRL_NODE_DEFERRED(node_id), (PINCTRL_MAP_ENTRY(node_id)), ())
+
+/* Add the pinctrl_dev_config for the log-uart nodes, that are not deferred init */
+#if DT_HAS_ALIAS(arduino_log_uart)
+#define PINCTRL_MAP_LOG_UART_ENTRY PINCTRL_MAP_ENTRY(DT_ALIAS(arduino_log_uart))
+#else
+#define PINCTRL_MAP_LOG_UART_ENTRY
+#endif
+
+static const struct pinctrl_map_entry pinctrl_map[] = {DT_FOREACH_STATUS_OKAY_NODE(
+	PINCTRL_MAP_ENTRY_IF_PRESENT) PINCTRL_MAP_LOG_UART_ENTRY{nullptr, nullptr}};
+
+#if defined(ARDUINO)
+#pragma pop_macro("ARDUINO")
+#endif
+
+/* Get pinctrl_dev_config for a device from the generated map. */
+static const struct pinctrl_dev_config *get_known_pcfg(const struct device *dev) {
+	for (size_t i = 0; i < ARRAY_SIZE(pinctrl_map); i++) {
+		if (pinctrl_map[i].dev == dev) {
+			return pinctrl_map[i].pcfg;
+		}
+	}
+
+	return nullptr;
+}
+
+/**
+ * @brief Initialize the peripheral and acquire a single pin to ARDUINO state.
+ *
+ * Switches peripheral pins back to ARDUINO pinctrl state (alternate function),
+ * typically after a temporary transition to GPIO mode.
+ *
+ * @param dev Pointer to the peripheral device
+ * @param state_pin_idx Index of the pin within the device's ARDUINO pinctrl state
+ * @return 0 on success, negative on error
+ */
+int init_dev_apply_channel_pinctrl(const struct device *dev, size_t state_pin_idx) {
+
+	if (dev == nullptr) {
+		return -EINVAL;
+	}
+
+	if (!device_is_ready(dev)) {
+		// init device for first usage, if not ready
+		int err = device_init(dev);
+		if (err < 0) {
+			return err;
+		}
+	}
+
+	const struct pinctrl_state *state;
+	const struct pinctrl_dev_config *pcfg = get_known_pcfg(dev);
 
-void _reinit_peripheral_if_needed(pin_size_t pin, const struct device *dev) {
-	if (pinmux_array[pin] != dev) {
-		pinmux_array[pin] = dev;
-		if (dev != NULL) {
-			dev->ops.init(dev);
+	if (pcfg == nullptr) {
+		/* Device not in DT mapping - add to pinctrl_map if needed */
+		return -ENOTSUP;
+	}
+
+	int err = pinctrl_lookup_state(pcfg, PINCTRL_STATE_ARDUINO, &state);
+	if (err < 0) {
+		return err; /* Fails if the state is not defined in pinctrl-names */
+	}
+
+	/* bounds check */
+	if (state_pin_idx >= state->pin_cnt) {
+		return -ERANGE;
+	}
+
+	/*
+	 * On platforms without CONFIG_PINCTRL_STORE_REG (e.g. STM32) the pcfg->reg is not present but
+	 * the argument is ignored by their pinctrl driver, so passing PINCTRL_REG_NONE is safe.
+	 */
+#ifdef CONFIG_PINCTRL_STORE_REG
+	uintptr_t reg = pcfg->reg;
+#else
+	uintptr_t reg = PINCTRL_REG_NONE;
+#endif
+
+	return pinctrl_configure_pins(&state->pins[state_pin_idx], 1, reg);
+}
+
+/**
+ * @brief Optimize peripheral transitions applying pinctrl state PINCTRL_STATE_DEFAULT.
+ *
+ * @param dev Target peripheral device to acquire pin for
+ */
+int init_dev_apply_pinctrl(const struct device *dev) {
+
+	if (dev == nullptr) {
+		return -EINVAL;
+	}
+
+	if (!device_is_ready(dev)) {
+		int ret = device_init(dev);
+		if (ret != 0 && ret != -EALREADY) {
+			return ret;
 		}
 	}
+
+	const struct pinctrl_dev_config *pcfg = get_known_pcfg(dev);
+	if (pcfg == nullptr) {
+		/* Device not in DT mapping - add to pinctrl_map if needed */
+		return -ENOTSUP;
+	}
+
+	return pinctrl_apply_state(pcfg, PINCTRL_STATE_DEFAULT);
 }
 
 static const struct gpio_dt_spec arduino_pins[] = {
@@ -143,6 +275,24 @@
 	}
 }
 
+/*
+ * Resolve pin index in a device ARDUINO pinctrl state from a DT spec array.
+ * The resulting index is the per-device ordinal at spec_idx.
+ */
+template <typename DT_SPEC, size_t N>
+static size_t state_pin_index_from_spec_index(const DT_SPEC (&specs)[N], size_t spec_idx) {
+	const struct device *dev = specs[spec_idx].dev;
+	size_t state_pin_idx = 0;
+
+	for (size_t i = 0; i < spec_idx; i++) {
+		if (specs[i].dev == dev) {
+			state_pin_idx++;
+		}
+	}
+
+	return state_pin_idx;
+}
+
 #ifdef CONFIG_PWM
 
 #define PWM_DT_SPEC(n, p, i) PWM_DT_SPEC_GET_BY_IDX(n, i),
@@ -216,7 +366,6 @@
 static const struct dac_channel_cfg dac_ch_cfg[] = {
 	DT_FOREACH_PROP_ELEM(DT_PATH(zephyr_user), dac_channels, DAC_CHANNEL_DEFINE)};
 
-static bool dac_channel_initialized[NUM_OF_DACS];
 #endif
 
 #endif
@@ -251,7 +400,6 @@
 void pinMode(pin_size_t pinNumber, PinMode pinMode) {
 	RETURN_ON_INVALID_PIN(pinNumber);
 
-	_reinit_peripheral_if_needed(pinNumber, NULL);
 	if (pinMode == INPUT) { // input mode
 		gpio_pin_configure_dt(&arduino_pins[pinNumber], GPIO_INPUT | GPIO_ACTIVE_HIGH);
 	} else if (pinMode == INPUT_PULLUP) { // input with internal pull-up
@@ -486,13 +634,15 @@
 		return;
 	}
 
+	(void)init_dev_apply_channel_pinctrl(arduino_pwm[idx].dev,
+										 state_pin_index_from_spec_index(arduino_pwm, idx));
+
 	if (!pwm_is_ready_dt(&arduino_pwm[idx])) {
 		pinMode(pinNumber, OUTPUT);
 		digitalWrite(pinNumber, value > 127 ? HIGH : LOW);
 		return;
 	}
 
-	_reinit_peripheral_if_needed(pinNumber, arduino_pwm[idx].dev);
 	value = CLAMP(value, 0, maxInput);
 
 	const uint32_t pulse = map64(value, 0, maxInput, 0, arduino_pwm[idx].period);
@@ -516,19 +666,13 @@
 		return;
 	}
 
-	if (!dac_channel_initialized[dacName]) {
-		if (!device_is_ready(dac_dev)) {
-			return;
-		}
+	// TODO: add reverse map to find pin name from DAC* define
+	// In the meantime, consider A0 == DAC0
+	(void)init_dev_apply_pinctrl(dac_dev);
 
-		// TODO: add reverse map to find pin name from DAC* define
-		// In the meantime, consider A0 == DAC0
-		_reinit_peripheral_if_needed((pin_size_t)(dacName + A0), dac_dev);
-		ret = dac_channel_setup(dac_dev, &dac_ch_cfg[dacName]);
-		if (ret != 0) {
-			return;
-		}
-		dac_channel_initialized[dacName] = true;
+	ret = dac_channel_setup(dac_dev, &dac_ch_cfg[dacName]);
+	if (ret != 0) {
+		return;
 	}
 
 	value = CLAMP(value, 0, maxInput);
@@ -586,7 +730,13 @@
 		return -ENOTSUP;
 	}
 
-	_reinit_peripheral_if_needed(pinNumber, arduino_adc[idx].dev);
+	/*
+	 * Init the ADC device for the first acquisition and restore only the required pin to analog mode when
+	 * transitioning from GPIO. The pin is selected from the ADC device "arduino" pinctrl state. Not
+	 * checking the return value because the device might not have pinctrl (e.g. nRF SAADC).
+	 */
+	(void)init_dev_apply_channel_pinctrl(arduino_adc[idx].dev,
+										 state_pin_index_from_spec_index(arduino_adc, idx));
 
 	err = adc_channel_setup(arduino_adc[idx].dev, &arduino_adc[idx].channel_cfg);
 	if (err < 0) {

cores/arduino/zephyrInternal.h

@@ -1,3 +1,3 @@
 /*
  * Copyright (c) 2024 Ayush Singh <ayush@beagleboard.org>
  *
@@ -14,7 +14,8 @@
 
 void enableInterrupt(pin_size_t);
 void disableInterrupt(pin_size_t);
-void _reinit_peripheral_if_needed(pin_size_t pin, const struct device *dev);
+
+int init_dev_apply_pinctrl(const struct device *dev); 
 
 #ifdef __cplusplus
 } // extern "C"

cores/arduino/zephyrSerial.cpp

@@ -1,3 +1,3 @@
 /*
  * Copyright (c) 2022 Dhruva Gole
  * Copyright (c) Arduino s.r.l. and/or its affiliated companies
@@ -5,7 +5,10 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+ #include "zephyrInternal.h"
+
 #include <zephyr/devicetree.h>
+#include <zephyr/drivers/pinctrl.h>
 #include <zephyr/drivers/uart.h>
 
 #include <api/HardwareSerial.h>
@@ -60,7 +63,10 @@
 		.flow_ctrl = UART_CFG_FLOW_CTRL_NONE,
 	};
 
-	_reinit_if_needed();
+	/* Re-apply DEFAULT pinctrl state so shared pins
+	 * are remuxed back to Serial after other peripherals have used them.
+	 */
+	(void)init_dev_apply_pinctrl(uart);
 
 	uart_configure(uart, &config);
 	uart_irq_callback_user_data_set(uart, arduino::ZephyrSerial::IrqDispatch, this);

cores/arduino/zephyrSerial.h

@@ -77,9 +77,7 @@ class ZephyrSerial : public HardwareSerial {
 
 	void end() {
 #ifdef CONFIG_DEVICE_DEINIT_SUPPORT
-		if (uart->ops.deinit) {
-			uart->ops.deinit(uart);
-		}
+		(void)device_deinit(uart);
 #endif
 	}
 
@@ -108,10 +106,6 @@ class ZephyrSerial : public HardwareSerial {
 	const struct device *uart;
 	ZephyrSerialBuffer<CONFIG_ARDUINO_API_SERIAL_BUFFER_SIZE> tx;
 	ZephyrSerialBuffer<CONFIG_ARDUINO_API_SERIAL_BUFFER_SIZE> rx;
-
-	virtual void _reinit_if_needed() {
-		uart->ops.init(uart);
-	}
 };
 
 } // namespace arduino