[v2,2/2] watchdog: Add the Watchdog Timer for the NXP S32 platform

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index f81705f8539a..4ab4275ef49f 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -792,6 +792,15 @@  config IMX7ULP_WDT
 	  To compile this driver as a module, choose M here: the
 	  module will be called imx7ulp_wdt.
 
+config S32G_WDT
+	tristate "S32G Watchdog"
+	depends on ARCH_S32 || COMPILE_TEST
+	select WATCHDOG_CORE
+	help
+	  This is the driver for the hardware watchdog on the NXP
+	  S32G platforms. If you wish to have watchdog support
+	  enabled, say Y, otherwise say N.
+
 config DB500_WATCHDOG
 	tristate "ST-Ericsson DB800 watchdog"
 	depends on MFD_DB8500_PRCMU
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 8411626fa162..d0f9826e32c3 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -69,6 +69,7 @@  obj-$(CONFIG_TS72XX_WATCHDOG) += ts72xx_wdt.o
 obj-$(CONFIG_IMX2_WDT) += imx2_wdt.o
 obj-$(CONFIG_IMX_SC_WDT) += imx_sc_wdt.o
 obj-$(CONFIG_IMX7ULP_WDT) += imx7ulp_wdt.o
+obj-$(CONFIG_S32G_WDT) += s32g_wdt.o
 obj-$(CONFIG_DB500_WATCHDOG) += db8500_wdt.o
 obj-$(CONFIG_RETU_WATCHDOG) += retu_wdt.o
 obj-$(CONFIG_BCM2835_WDT) += bcm2835_wdt.o
diff --git a/drivers/watchdog/s32g_wdt.c b/drivers/watchdog/s32g_wdt.c
new file mode 100644
index 000000000000..a585ff1b372c
--- /dev/null
+++ b/drivers/watchdog/s32g_wdt.c
@@ -0,0 +1,313 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Watchdog driver for S32G SoC
+ *
+ * Copyright 2017-2019, 2021-2025 NXP.
+ *
+ */
+#include <linux/clk.h>
+#include <linux/debugfs.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/watchdog.h>
+
+#define DRIVER_NAME "s32g-swt"
+
+#define S32G_SWT_CR(__base)	((__base) + 0x00)	/* Control Register offset	*/
+#define S32G_SWT_CR_SM		(BIT(9) | BIT(10))	/* -> Service Mode		*/
+#define S32G_SWT_CR_STP		BIT(2)			/* -> Stop Mode Control		*/
+#define S32G_SWT_CR_FRZ		BIT(1)			/* -> Debug Mode Control	*/
+#define S32G_SWT_CR_WEN		BIT(0)			/* -> Watchdog Enable		*/
+
+#define S32G_SWT_TO(__base)	((__base) + 0x08)	/* Timeout Register offset	*/
+
+#define S32G_SWT_SR(__base)	((__base) + 0x10)	/* Service Register offset	*/
+#define S32G_WDT_SEQ1		0xA602			/* -> service sequence number 1	*/
+#define S32G_WDT_SEQ2		0xB480			/* -> service sequence number 2	*/
+
+#define S32G_SWT_CO(__base)	((__base) + 0x14)	/* Counter output register	*/
+
+#define S32G_WDT_DEFAULT_TIMEOUT	30
+
+struct s32g_wdt_device {
+	int rate;
+	void __iomem *base;
+	struct watchdog_device wdog;
+};
+
+static bool nowayout = WATCHDOG_NOWAYOUT;
+module_param(nowayout, bool, 0);
+MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
+		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+
+static unsigned int timeout_param = S32G_WDT_DEFAULT_TIMEOUT;
+module_param(timeout_param, uint, 0);
+MODULE_PARM_DESC(timeout_param, "Watchdog timeout in seconds (default="
+		 __MODULE_STRING(S32G_WDT_DEFAULT_TIMEOUT) ")");
+
+static bool early_enable;
+module_param(early_enable, bool, 0);
+MODULE_PARM_DESC(early_enable,
+		 "Watchdog is started on module insertion (default=false)");
+
+static const struct watchdog_info s32g_wdt_info = {
+	.identity = "s32g watchdog",
+	.options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
+	WDIOC_GETTIMEOUT | WDIOC_GETTIMELEFT,
+};
+
+static struct s32g_wdt_device *wdd_to_s32g_wdt(struct watchdog_device *wdd)
+{
+	return container_of(wdd, struct s32g_wdt_device, wdog);
+}
+
+static unsigned int wdog_sec_to_count(struct s32g_wdt_device *wdev, unsigned int timeout)
+{
+	return wdev->rate * timeout;
+}
+
+static int s32g_wdt_ping(struct watchdog_device *wdog)
+{
+	struct s32g_wdt_device *wdev = wdd_to_s32g_wdt(wdog);
+
+	writel(S32G_WDT_SEQ1, S32G_SWT_SR(wdev->base));
+	writel(S32G_WDT_SEQ2, S32G_SWT_SR(wdev->base));
+
+	return 0;
+}
+
+static int s32g_wdt_start(struct watchdog_device *wdog)
+{
+	struct s32g_wdt_device *wdev = wdd_to_s32g_wdt(wdog);
+	unsigned long val;
+
+	val = readl(S32G_SWT_CR(wdev->base));
+
+	val |= S32G_SWT_CR_WEN;
+
+	writel(val, S32G_SWT_CR(wdev->base));
+
+	return 0;
+}
+
+static int s32g_wdt_stop(struct watchdog_device *wdog)
+{
+	struct s32g_wdt_device *wdev = wdd_to_s32g_wdt(wdog);
+	unsigned long val;
+
+	val = readl(S32G_SWT_CR(wdev->base));
+
+	val &= ~S32G_SWT_CR_WEN;
+
+	writel(val, S32G_SWT_CR(wdev->base));
+
+	return 0;
+}
+
+static int s32g_wdt_set_timeout(struct watchdog_device *wdog, unsigned int timeout)
+{
+	struct s32g_wdt_device *wdev = wdd_to_s32g_wdt(wdog);
+
+	writel(wdog_sec_to_count(wdev, timeout), S32G_SWT_TO(wdev->base));
+
+	/*
+	 * Conforming to the documentation, the timeout counter is
+	 * loaded when servicing is operated (aka ping) or when the
+	 * counter is enabled. In case the watchdog is already started
+	 * it must be stopped and started again to update the timeout
+	 * register or a ping can be sent to refresh the counter. Here
+	 * we choose to send a ping to the watchdog which is harmless
+	 * if the watchdog is stopped.
+	 */
+	return s32g_wdt_ping(wdog);
+}
+
+static unsigned int s32g_wdt_get_timeleft(struct watchdog_device *wdog)
+{
+	struct s32g_wdt_device *wdev = wdd_to_s32g_wdt(wdog);
+	unsigned long counter;
+	bool is_running;
+
+	/*
+	 * The counter output can be read only if the SWT is
+	 * disabled. Given the latency between the internal counter
+	 * and the counter output update, there can be very small
+	 * difference. However, we can accept this matter of fact
+	 * given the resolution is a second based unit for the output.
+	 */
+	is_running = watchdog_hw_running(wdog);
+
+	if (is_running)
+		s32g_wdt_stop(wdog);
+
+	counter = readl(S32G_SWT_CO(wdev->base));
+
+	if (is_running)
+		s32g_wdt_start(wdog);
+
+	return counter / wdev->rate;
+}
+
+static const struct watchdog_ops s32g_wdt_ops = {
+	.owner		= THIS_MODULE,
+	.start		= s32g_wdt_start,
+	.stop		= s32g_wdt_stop,
+	.ping		= s32g_wdt_ping,
+	.set_timeout	= s32g_wdt_set_timeout,
+	.get_timeleft	= s32g_wdt_get_timeleft,
+};
+
+static void s32g_wdt_init(struct s32g_wdt_device *wdev)
+{
+	unsigned long val;
+
+	/* Set the watchdog's Time-Out value */
+	val = wdog_sec_to_count(wdev, wdev->wdog.timeout);
+
+	writel(val, S32G_SWT_TO(wdev->base));
+
+	/*
+	 * Get the control register content. We are at init time, the
+	 * watchdog should not be started.
+	 */
+	val = readl(S32G_SWT_CR(wdev->base));
+
+	/*
+	 * We want to allow the watchdog timer to be stopped when
+	 * device enters debug mode.
+	 */
+	val |= S32G_SWT_CR_FRZ;
+
+	/*
+	 * However, when the CPU is in WFI or suspend mode, the
+	 * watchdog must continue. The documentation refers it as the
+	 * stopped mode.
+	 */
+	val &= ~S32G_SWT_CR_STP;
+
+	/*
+	 * Use Fixed Service Sequence to ping the watchdog which is
+	 * 0x00 configuration value for the service mode. It should be
+	 * already set because it is the default value but we reset it
+	 * in case.
+	 */
+	val &= ~S32G_SWT_CR_SM;
+
+	writel(val, S32G_SWT_CR(wdev->base));
+
+	/*
+	 * When the 'early_enable' option is set, we start the
+	 * watchdog from the kernel.
+	 */
+	if (early_enable) {
+		s32g_wdt_start(&wdev->wdog);
+		set_bit(WDOG_HW_RUNNING, &wdev->wdog.status);
+	}
+}
+
+static int s32g_wdt_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct resource *res;
+	struct clk *clk;
+	struct s32g_wdt_device *wdev;
+	struct watchdog_device *wdog;
+	int ret;
+
+	wdev = devm_kzalloc(dev, sizeof(*wdev), GFP_KERNEL);
+	if (!wdev)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	wdev->base = devm_ioremap_resource(dev, res);
+	if (IS_ERR(wdev->base))
+		return dev_err_probe(&pdev->dev, PTR_ERR(wdev->base), "Can not get resource\n");
+
+	clk = devm_clk_get_enabled(dev, NULL);
+	if (IS_ERR(clk))
+		return dev_err_probe(dev, PTR_ERR(clk), "Can't get Watchdog clock\n");
+
+	wdev->rate = clk_get_rate(clk);
+	if (!wdev->rate) {
+		dev_err(dev, "Input clock rate is not valid\n");
+		return -EINVAL;
+	}
+
+	wdog = &wdev->wdog;
+	wdog->info = &s32g_wdt_info;
+	wdog->ops = &s32g_wdt_ops;
+
+	/*
+	 * The code converts the timeout into a counter a value, if
+	 * the value is less than 0x100, then it is clamped by the SWT
+	 * module, so it is safe to specify a zero value as the
+	 * minimum timeout.
+	 */
+	wdog->min_timeout = 0;
+
+	/*
+	 * The counter register is a 32 bits long, so the maximum
+	 * counter value is UINT_MAX and the timeout in second is the
+	 * value divided by the rate.
+	 *
+	 * For instance, a rate of 51MHz lead to 84 seconds maximum
+	 * timeout.
+	 */
+	wdog->max_timeout = UINT_MAX / wdev->rate;
+
+	/*
+	 * The module param and the DT 'timeout-sec' property will
+	 * override the default value if they are specified.
+	 */
+	ret = watchdog_init_timeout(wdog, timeout_param, dev);
+	if (ret)
+		return ret;
+
+	/*
+	 * As soon as the watchdog is started, there is no way to stop
+	 * it if the 'nowayout' option is set at boot time
+	 */
+	watchdog_set_nowayout(wdog, nowayout);
+
+	/*
+	 * The devm_ version of the watchdog_register_device()
+	 * function will call watchdog_unregister_device() when the
+	 * device is removed.
+	 */
+	watchdog_stop_on_unregister(wdog);
+
+	s32g_wdt_init(wdev);
+
+	ret = devm_watchdog_register_device(dev, wdog);
+	if (ret)
+		return dev_err_probe(dev, ret, "Cannot register watchdog device\n");
+
+	dev_info(dev, "S32G Watchdog Timer Registered, timeout=%ds, nowayout=%d, early_enable=%d\n",
+		 wdog->timeout, nowayout, early_enable);
+
+	return 0;
+}
+
+static const struct of_device_id s32g_wdt_dt_ids[] = {
+	{ .compatible = "nxp,s32g2-swt" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, s32g_wdt_dt_ids);
+
+static struct platform_driver s32g_wdt_driver = {
+	.probe = s32g_wdt_probe,
+	.driver = {
+		.name = DRIVER_NAME,
+		.of_match_table = s32g_wdt_dt_ids,
+	},
+};
+
+module_platform_driver(s32g_wdt_driver);
+
+MODULE_AUTHOR("Daniel Lezcano <daniel.lezcano@linaro.org>");
+MODULE_DESCRIPTION("Watchdog driver for S32G SoC");
+MODULE_LICENSE("GPL");