drivers: watchdog: Add Raspberry Pi Pico watchdog driver

This adds basic support for the watchdog timer on the RP2040 MCU and
Raspberry Pi Pico development board

Signed-off-by: Jamie McCrae <spam@helper3000.net>

CODEOWNERS

@@ -443,6 +443,7 @@
 /drivers/watchdog/wdt_ite_it8xxx2.c       @RuibinChang
 /drivers/watchdog/Kconfig.it8xxx2         @RuibinChang
 /drivers/watchdog/wdt_counter.c           @nordic-krch
+/drivers/watchdog/*rpi_pico*              @thedjnK
 /drivers/wifi/                            @rlubos @tbursztyka @pfalcon
 /drivers/wifi/esp_at/                     @mniestroj
 /drivers/wifi/eswifi/                     @loicpoulain @nandojve

boards/arm/rpi_pico/rpi_pico.dts

@@ -28,8 +28,15 @@
 		};
 	};
 
+	xtal_clk: xtal-clk {
+		compatible = "fixed-clock";
+		clock-frequency = <12000000>;
+		#clock-cells = <0>;
+	};
+
 	aliases {
 		led0 = &led0;
+		watchdog0 = &wdt0;
 	};
 };
 
@@ -85,6 +92,10 @@
 	pinctrl-names = "default";
 };
 
+&wdt0 {
+	status = "okay";
+};
+
 zephyr_udc0: &usbd {
 	status = "okay";
 };

drivers/watchdog/CMakeLists.txt

@@ -17,6 +17,7 @@ zephyr_library_sources_ifdef(CONFIG_WDT_MCUX_WDOG32 wdt_mcux_wdog32.c)
 zephyr_library_sources_ifdef(CONFIG_WDT_MCUX_WWDT wdt_mcux_wwdt.c)
 zephyr_library_sources_ifdef(CONFIG_WDT_NPCX wdt_npcx.c)
 zephyr_library_sources_ifdef(CONFIG_WDT_NRFX wdt_nrfx.c)
+zephyr_library_sources_ifdef(CONFIG_WDT_RPI_PICO wdt_rpi_pico.c)
 zephyr_library_sources_ifdef(CONFIG_WDT_SAM wdt_sam.c)
 zephyr_library_sources_ifdef(CONFIG_WDT_SAM0 wdt_sam0.c)
 zephyr_library_sources_ifdef(CONFIG_WDT_SIFIVE wdt_sifive.c)

drivers/watchdog/Kconfig

@@ -82,4 +82,7 @@ source "drivers/watchdog/Kconfig.npcx"
 source "drivers/watchdog/Kconfig.cc32xx"
 
 source "drivers/watchdog/Kconfig.it8xxx2"
+
+source "drivers/watchdog/Kconfig.rpi_pico"
+
 endif

drivers/watchdog/Kconfig.rpi_pico

@@ -0,0 +1,20 @@
+# Copyright (c) 2022, Jamie McCrae
+# SPDX-License-Identifier: Apache-2.0
+
+DT_COMPAT_RASPBERRYPI_PICO_WATCHDOG := raspberrypi,pico-watchdog
+
+config WDT_RPI_PICO
+	bool "Raspberry Pi Pico Watchdog driver"
+	default $(dt_compat_enabled,$(DT_COMPAT_RASPBERRYPI_PICO_WATCHDOG))
+	depends on SOC_FAMILY_RPI_PICO
+
+config WDT_RPI_PICO_INITIAL_TIMEOUT
+	int "Default watchdog timeout in us"
+	depends on WDT_RPI_PICO
+	default 8388607
+	range 1 8388607
+	help
+	  Sets the default watchdog timeout at start-up, the feed function must
+	  be called every interval prior to this time elapsing to prevent a
+	  reboot of the module. The default is just over 8 seconds, which is the
+	  largest timeout possible.

drivers/watchdog/wdt_rpi_pico.c

@@ -0,0 +1,171 @@
+/*
+ * Copyright (c) 2022, Jamie McCrae
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#define DT_DRV_COMPAT raspberrypi_pico_watchdog
+
+#include <hardware/watchdog.h>
+#include <hardware/structs/psm.h>
+#include <zephyr/drivers/watchdog.h>
+
+#include <zephyr/logging/log.h>
+LOG_MODULE_REGISTER(wdt_rpi_pico, CONFIG_WDT_LOG_LEVEL);
+
+/* Maximum watchdog time is halved due to errata RP2040-E1 */
+#define RPI_PICO_MAX_WDT_TIME (0xffffff / 2)
+#define RPI_PICO_WDT_TIME_MULTIPLICATION_FACTOR 2
+
+/* Watchdog requires a 1MHz clock source, divided from the crystal oscillator */
+#define RPI_PICO_XTAL_FREQ_WDT_TICK_DIVISOR 1000000
+
+struct wdt_rpi_pico_data {
+	uint8_t reset_type;
+	uint32_t load;
+	bool enabled;
+};
+
+struct wdt_rpi_pico_config {
+	uint32_t xtal_frequency;
+};
+
+static int wdt_rpi_pico_setup(const struct device *dev, uint8_t options)
+{
+	const struct wdt_rpi_pico_config *config = dev->config;
+	struct wdt_rpi_pico_data *data = dev->data;
+
+	if ((options & WDT_OPT_PAUSE_IN_SLEEP) == 1) {
+		return -ENOTSUP;
+	}
+
+	hw_clear_bits(&watchdog_hw->ctrl, WATCHDOG_CTRL_ENABLE_BITS);
+
+	psm_hw->wdsel = 0;
+
+	/* TODO: Handle individual core reset when SMP support for RP2040 is added */
+	if (data->reset_type == WDT_FLAG_RESET_SOC) {
+		hw_set_bits(&psm_hw->wdsel, PSM_WDSEL_BITS);
+	} else if (data->reset_type == WDT_FLAG_RESET_CPU_CORE) {
+		hw_set_bits(&psm_hw->wdsel, PSM_WDSEL_PROC0_BITS);
+	}
+
+	if ((options & WDT_OPT_PAUSE_HALTED_BY_DBG) == 0) {
+		hw_clear_bits(&watchdog_hw->ctrl,
+			      (WATCHDOG_CTRL_PAUSE_JTAG_BITS | WATCHDOG_CTRL_PAUSE_DBG0_BITS |
+			       WATCHDOG_CTRL_PAUSE_DBG1_BITS));
+	} else {
+		hw_set_bits(&watchdog_hw->ctrl,
+			    (WATCHDOG_CTRL_PAUSE_JTAG_BITS | WATCHDOG_CTRL_PAUSE_DBG0_BITS |
+			     WATCHDOG_CTRL_PAUSE_DBG1_BITS));
+	}
+
+	watchdog_hw->load = data->load;
+
+	/* Zero out the scratch registers so that the module reboots at the
+	 * default program counter
+	 */
+	watchdog_hw->scratch[4] = 0;
+	watchdog_hw->scratch[5] = 0;
+	watchdog_hw->scratch[6] = 0;
+	watchdog_hw->scratch[7] = 0;
+
+	hw_set_bits(&watchdog_hw->ctrl, WATCHDOG_CTRL_ENABLE_BITS);
+
+	data->enabled = true;
+
+	watchdog_hw->tick = (config->xtal_frequency / RPI_PICO_XTAL_FREQ_WDT_TICK_DIVISOR) |
+			    WATCHDOG_TICK_ENABLE_BITS;
+
+	return 0;
+}
+
+static int wdt_rpi_pico_disable(const struct device *dev)
+{
+	struct wdt_rpi_pico_data *data = dev->data;
+
+	if (data->enabled == false) {
+		return -EFAULT;
+	}
+
+	hw_clear_bits(&watchdog_hw->ctrl, WATCHDOG_CTRL_ENABLE_BITS);
+
+	data->enabled = false;
+
+	return 0;
+}
+
+static int wdt_rpi_pico_install_timeout(const struct device *dev, const struct wdt_timeout_cfg *cfg)
+{
+	struct wdt_rpi_pico_data *data = dev->data;
+
+	if (cfg->window.min != 0U || cfg->window.max == 0U) {
+		return -EINVAL;
+	} else if (cfg->window.max > RPI_PICO_MAX_WDT_TIME) {
+		return -EINVAL;
+	} else if (cfg->callback != NULL) {
+		return -ENOTSUP;
+	} else if ((cfg->flags & WDT_FLAG_RESET_MASK) == WDT_FLAG_RESET_NONE) {
+		/* The RP2040 does technically support this mode, but requires
+		 * a program counter and stack pointer value to be set,
+		 * therefore do not allow configuring in this mode
+		 */
+		return -EINVAL;
+	}
+
+	data->load = (cfg->window.max * RPI_PICO_WDT_TIME_MULTIPLICATION_FACTOR);
+	data->reset_type = (cfg->flags & WDT_FLAG_RESET_MASK);
+
+	return 0;
+}
+
+static int wdt_rpi_pico_feed(const struct device *dev, int channel_id)
+{
+	struct wdt_rpi_pico_data *data = dev->data;
+
+	if (channel_id != 0) {
+		/* There is only one input to the watchdog */
+		return -EINVAL;
+	}
+
+	if (data->enabled == false) {
+		/* Watchdog is not running so does not need to be fed */
+		return -EINVAL;
+	}
+
+	watchdog_hw->load = data->load;
+
+	return 0;
+}
+
+static int wdt_rpi_pico_init(const struct device *dev)
+{
+#ifndef CONFIG_WDT_DISABLE_AT_BOOT
+	return wdt_rpi_pico_setup(dev, WDT_OPT_PAUSE_HALTED_BY_DBG);
+#endif
+
+	return 0;
+}
+
+static const struct wdt_driver_api wdt_rpi_pico_driver_api = {
+	.setup = wdt_rpi_pico_setup,
+	.disable = wdt_rpi_pico_disable,
+	.install_timeout = wdt_rpi_pico_install_timeout,
+	.feed = wdt_rpi_pico_feed,
+};
+
+#define WDT_RPI_PICO_WDT_DEVICE(idx)                                                               \
+	static const struct wdt_rpi_pico_config wdt_##idx##_config = {                             \
+		.xtal_frequency = DT_INST_PROP_BY_PHANDLE(idx, clocks, clock_frequency)            \
+	};                                                                                         \
+	static struct wdt_rpi_pico_data wdt_##idx##_data = {                                       \
+		.reset_type = WDT_FLAG_RESET_SOC,                                                  \
+		.load = (CONFIG_WDT_RPI_PICO_INITIAL_TIMEOUT *                                     \
+			 RPI_PICO_WDT_TIME_MULTIPLICATION_FACTOR),                                 \
+		.enabled = false                                                                   \
+	};                                                                                         \
+	DEVICE_DT_DEFINE(DT_NODELABEL(wdt##idx), wdt_rpi_pico_init, NULL, &wdt_##idx##_data,       \
+			 &wdt_##idx##_config, PRE_KERNEL_1, CONFIG_KERNEL_INIT_PRIORITY_DEVICE,    \
+			 &wdt_rpi_pico_driver_api)
+
+DT_INST_FOREACH_STATUS_OKAY(WDT_RPI_PICO_WDT_DEVICE);

dts/arm/rpi_pico/rp2040.dtsi

@@ -125,6 +125,14 @@
 			status = "disabled";
 		};
 
+		wdt0: watchdog@40058000 {
+			compatible = "raspberrypi,pico-watchdog";
+			reg = <0x40058000 DT_SIZE_K(4)>;
+			clocks = <&xtal_clk>;
+			label = "WDT_0";
+			status = "disabled";
+		};
+
 		usbd: usbd@50100000 {
 			compatible = "raspberrypi,pico-usbd";
 			reg = <0x50100000 0x10000>;

dts/bindings/watchdog/raspberrypi,pico-watchdog.yaml

@@ -0,0 +1,19 @@
+# Copyright (c) 2022, Jamie McCrae
+# SPDX-License-Identifier: Apache-2.0
+
+description: Raspberry Pi Pico Watchdog
+
+compatible: "raspberrypi,pico-watchdog"
+
+include: base.yaml
+
+properties:
+    reg:
+      required: true
+
+    label:
+      required: true
+
+    clocks:
+      required: true
+      description: Crystal oscillator source clock