Add support for Xilinx Window Watchdog driver

drivers/watchdog/CMakeLists.txt

@@ -48,6 +48,7 @@ zephyr_library_sources_ifdef(CONFIG_WDT_AMBIQ wdt_ambiq.c)
 zephyr_library_sources_ifdef(CONFIG_WDT_XMC4XXX wdt_xmc4xxx.c)
 zephyr_library_sources_ifdef(CONFIG_WWDT_NUMAKER wdt_wwdt_numaker.c)
 zephyr_library_sources_ifdef(CONFIG_WDT_ENE_KB1200 wdt_ene_kb1200.c)
+zephyr_library_sources_ifdef(CONFIG_XILINX_WINDOW_WATCHDOG wdt_xilinx_wwdt.c)
 
 zephyr_library_sources_ifdef(CONFIG_WDT_DW wdt_dw.c wdt_dw_common.c)
 zephyr_library_sources_ifdef(CONFIG_WDT_INTEL_ADSP wdt_intel_adsp.c wdt_dw_common.c)

drivers/watchdog/Kconfig

@@ -143,4 +143,6 @@ source "drivers/watchdog/Kconfig.ene"
 
 source "drivers/watchdog/Kconfig.litex"
 
+source "drivers/watchdog/Kconfig.xilinx_wwdt"
+
 endif # WATCHDOG

drivers/watchdog/Kconfig.xilinx_wwdt

@@ -0,0 +1,16 @@
+# Copyright (c) 2025 Advanced Micro Devices, Inc.
+# SPDX-License-Identifier: Apache-2.0
+
+config XILINX_WINDOW_WATCHDOG
+	bool "Xilinx window watchdog driver"
+	default y
+	depends on DT_HAS_XLNX_VERSAL_WWDT_ENABLED
+	help
+	  Enable Window watchdog driver for the versal_wwdt IP core.
+	  Window watchdog timer(WWDT) contains closed(first) and
+	  open(second) window with 32 bit width. Write to the watchdog
+	  timer within predefined window periods of time. This means
+	  a period that is not too soon and a period that is not too
+	  late. The WWDT has to be restarted within the open window time.
+	  If software tries to restart WWDT outside of the open window
+	  time period, it generates a SOC reset.

drivers/watchdog/wdt_xilinx_wwdt.c

@@ -0,0 +1,274 @@
+/*
+ * Copyright (c) 2025 Advanced Micro Devices, Inc.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#define DT_DRV_COMPAT xlnx_versal_wwdt
+
+#include <errno.h>
+#include <zephyr/device.h>
+#include <zephyr/kernel.h>
+#include <zephyr/drivers/hwinfo.h>
+#include <zephyr/drivers/watchdog.h>
+#include <zephyr/logging/log.h>
+#include <zephyr/sys/util.h>
+
+LOG_MODULE_REGISTER(xilinx_wwdt, CONFIG_WDT_LOG_LEVEL);
+
+/* Register offsets for the WWDT device */
+#define XWWDT_MWR_OFFSET	0x00
+#define XWWDT_ESR_OFFSET	0x04
+#define XWWDT_FCR_OFFSET	0x08
+#define XWWDT_FWR_OFFSET	0x0c
+#define XWWDT_SWR_OFFSET	0x10
+
+/* Master Write Control Register Masks */
+#define XWWDT_MWR_MASK	BIT(0)
+
+/* Enable and Status Register Masks */
+#define XWWDT_ESR_WINT_MASK	BIT(16)
+#define XWWDT_ESR_WSW_MASK	BIT(8)
+#define XWWDT_ESR_WEN_MASK	BIT(0)
+
+/* Watchdog Second Window Shift */
+#define XWWDT_ESR_WSW_SHIFT	8U
+
+/* Maximum count value of each 32 bit window */
+#define XWWDT_MAX_COUNT_WINDOW	GENMASK(31, 0)
+
+/* Maximum count value of closed and open window combined */
+#define XWWDT_MAX_COUNT_WINDOW_COMBINED	GENMASK64(32, 1)
+
+struct xilinx_wwdt_config {
+	uint32_t wdt_clock_freq;
+	uint32_t timeout_sec;
+	mem_addr_t base;
+};
+
+struct xilinx_wwdt_data {
+	struct k_spinlock lock;
+	bool timeout_active;
+	bool wdt_started;
+};
+
+static int wdt_xilinx_wwdt_setup(const struct device *dev, uint8_t options)
+{
+	const struct xilinx_wwdt_config *config = dev->config;
+	struct xilinx_wwdt_data *data = dev->data;
+	uint32_t reg_value;
+	uint32_t ret = 0;
+
+	k_spinlock_key_t key = k_spin_lock(&data->lock);
+
+	if (!data->timeout_active) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (data->wdt_started) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	/*
+	 * There is no control at driver level whether the WDT pauses in CPU sleep
+	 * or when halted by debugger. Hence there is no check for the options.
+	 */
+
+	/* Read enable status register and update WEN bit */
+	reg_value = sys_read32(config->base + XWWDT_ESR_OFFSET) | XWWDT_ESR_WEN_MASK;
+
+	/* Write enable status register with updated WEN value */
+	sys_write32(reg_value, config->base + XWWDT_ESR_OFFSET);
+	data->wdt_started = true;
+out:
+	k_spin_unlock(&data->lock, key);
+	return ret;
+}
+
+static int wdt_xilinx_wwdt_install_timeout(const struct device *dev,
+					   const struct wdt_timeout_cfg *cfg)
+{
+	const struct xilinx_wwdt_config *config = dev->config;
+	struct xilinx_wwdt_data *data = dev->data;
+	uint64_t closed_window_ms_count;
+	uint64_t open_window_ms_count;
+	uint64_t max_hw_timeout_ms;
+	uint64_t timeout_ms_count;
+	uint32_t timeout_ms;
+	uint64_t ms_count;
+	uint32_t ret = 0;
+
+	k_spinlock_key_t key = k_spin_lock(&data->lock);
+
+	if (data->wdt_started) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	if (cfg->flags != WDT_FLAG_RESET_SOC) {
+		ret = -ENOTSUP;
+		goto out;
+	}
+
+	timeout_ms = config->timeout_sec * 1000;
+	max_hw_timeout_ms = (XWWDT_MAX_COUNT_WINDOW_COMBINED * 1000) / config->wdt_clock_freq;
+
+	/*
+	 * If the maximum limit of the window is passed from the user space,
+	 * overwrite the timeout with this value.
+	 */
+	if (cfg->window.max > 0) {
+		timeout_ms = cfg->window.max;
+	}
+
+	/* Timeout greater than the maximum hardware timeout is invalid. */
+	if (timeout_ms > max_hw_timeout_ms) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* Calculate ticks for 1 milli-second */
+	ms_count = (config->wdt_clock_freq) / 1000;
+	timeout_ms_count = timeout_ms * ms_count;
+
+	closed_window_ms_count = cfg->window.min * ms_count;
+	if (closed_window_ms_count > XWWDT_MAX_COUNT_WINDOW) {
+		LOG_ERR("The closed window timeout is invalid.");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	open_window_ms_count = timeout_ms_count - closed_window_ms_count;
+	if (open_window_ms_count > XWWDT_MAX_COUNT_WINDOW) {
+		LOG_ERR("The open window timeout is invalid.");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	sys_write32(XWWDT_MWR_MASK, config->base + XWWDT_MWR_OFFSET);
+	sys_write32(~(uint32_t)XWWDT_ESR_WEN_MASK, config->base + XWWDT_ESR_OFFSET);
+	sys_write32(closed_window_ms_count, config->base + XWWDT_FWR_OFFSET);
+	sys_write32(open_window_ms_count, config->base + XWWDT_SWR_OFFSET);
+
+	data->timeout_active = true;
+out:
+	k_spin_unlock(&data->lock, key);
+	return ret;
+}
+
+static int wdt_xilinx_wwdt_feed(const struct device *dev, int channel_id)
+{
+	const struct xilinx_wwdt_config *config = dev->config;
+	struct xilinx_wwdt_data *data = dev->data;
+	uint32_t control_status_reg;
+	uint32_t is_sec_window;
+	uint32_t ret = 0;
+
+	k_spinlock_key_t key = k_spin_lock(&data->lock);
+
+	if (channel_id != 0 || !data->timeout_active) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* Enable write access control bit for the WWDT. */
+	sys_write32(XWWDT_MWR_MASK, config->base + XWWDT_MWR_OFFSET);
+
+	/* Trigger restart kick to WWDT. */
+	control_status_reg = sys_read32(config->base + XWWDT_ESR_OFFSET);
+
+	/* Check if WWDT is in Second window. */
+	is_sec_window = (control_status_reg & (uint32_t)XWWDT_ESR_WSW_MASK) >> XWWDT_ESR_WSW_SHIFT;
+
+	if (is_sec_window != 1) {
+		LOG_ERR("Feed in Closed window is not supported.");
+		ret = -ENOTSUP;
+		goto out;
+	}
+
+	control_status_reg |= (uint32_t)XWWDT_ESR_WSW_MASK;
+	sys_write32(control_status_reg, config->base + XWWDT_ESR_OFFSET);
+out:
+	k_spin_unlock(&data->lock, key);
+	return ret;
+}
+
+static int wdt_xilinx_wwdt_disable(const struct device *dev)
+{
+	const struct xilinx_wwdt_config *config = dev->config;
+	struct xilinx_wwdt_data *data = dev->data;
+	uint32_t is_wwdt_enable;
+	uint32_t is_sec_window;
+	uint32_t reg_value;
+	uint32_t ret = 0;
+
+	k_spinlock_key_t key = k_spin_lock(&data->lock);
+
+	is_wwdt_enable = sys_read32(config->base + XWWDT_ESR_OFFSET) & XWWDT_ESR_WEN_MASK;
+
+	if (is_wwdt_enable == 0) {
+		ret = -EFAULT;
+		goto out;
+	}
+
+	/* Read enable status register and check if WWDT is in open window. */
+	is_sec_window = (sys_read32(config->base + XWWDT_ESR_OFFSET) & XWWDT_ESR_WSW_MASK) >>
+				   XWWDT_ESR_WSW_SHIFT;
+
+	if (is_sec_window != 1)	{
+		LOG_ERR("Disabling WWDT in closed window is not allowed.");
+		ret = -EPERM;
+		goto out;
+	}
+
+	/* Read enable status register and update WEN bit. */
+	reg_value = sys_read32(config->base + XWWDT_ESR_OFFSET) & (~XWWDT_ESR_WEN_MASK);
+
+	/* Set WSW bit to zero. It is RW1C bit. */
+	reg_value &= ~((uint32_t)XWWDT_ESR_WSW_MASK);
+
+	/* Write enable status register with updated WEN and WSW value. */
+	sys_write32(reg_value, config->base + XWWDT_ESR_OFFSET);
+
+	data->wdt_started = false;
+out:
+	k_spin_unlock(&data->lock, key);
+	return ret;
+}
+
+static int wdt_xilinx_wwdt_init(const struct device *dev)
+{
+	const struct xilinx_wwdt_config *config = dev->config;
+	uint32_t ret = 0;
+
+	if (config->timeout_sec == 0) {
+		return -EINVAL;
+	}
+
+	return ret;
+}
+
+static DEVICE_API(wdt, wdt_xilinx_wwdt_api) = {
+	.setup = wdt_xilinx_wwdt_setup,
+	.install_timeout = wdt_xilinx_wwdt_install_timeout,
+	.feed = wdt_xilinx_wwdt_feed,
+	.disable = wdt_xilinx_wwdt_disable,
+};
+
+#define WDT_XILINX_WWDT_INIT(inst)								\
+	static struct xilinx_wwdt_data wdt_xilinx_wwdt_##inst##_dev_data;			\
+												\
+	static const struct xilinx_wwdt_config wdt_xilinx_wwdt_##inst##_cfg = {			\
+		.base = DT_INST_REG_ADDR(inst),							\
+		.timeout_sec = DT_INST_PROP(inst, timeout_sec),					\
+		.wdt_clock_freq = DT_INST_PROP_BY_PHANDLE(inst, clocks, clock_frequency),	\
+	};											\
+												\
+	DEVICE_DT_INST_DEFINE(inst, &wdt_xilinx_wwdt_init, NULL,				\
+				&wdt_xilinx_wwdt_##inst##_dev_data,				\
+				&wdt_xilinx_wwdt_##inst##_cfg, PRE_KERNEL_1,			\
+				CONFIG_KERNEL_INIT_PRIORITY_DEVICE, &wdt_xilinx_wwdt_api);
+
+DT_INST_FOREACH_STATUS_OKAY(WDT_XILINX_WWDT_INIT)

dts/bindings/watchdog/xlnx,versal-wwdt.yaml

@@ -0,0 +1,21 @@
+# Copyright (c) 2025 Advanced Micro Devices, Inc.
+# SPDX-License-Identifier: Apache-2.0
+
+description: Xilinx window watchdog
+
+compatible: "xlnx,versal-wwdt"
+
+include: base.yaml
+
+properties:
+  reg:
+    required: true
+
+  timeout-sec:
+    type: int
+    required: true
+    description: Timeout value in seconds.
+
+  clocks:
+    required: true
+    description: Reference to clock for window watchdog core.