watchdog: Add support for Airoha EN7851 watchdog

Add support for Airoha EN7851 watchdog. This is a very basic watchdog
with no pretimeout support, max timeout is 28 seconds and it ticks based
on half the SoC BUS clock.

Signed-off-by: Christian Marangi <[e-mail]>
Reviewed-by: Guenter Roeck <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Guenter Roeck <[e-mail]>
Signed-off-by: Wim Van Sebroeck <[e-mail]>

drivers/watchdog/Kconfig

···
 
 # ARM Architecture
 
+config AIROHA_WATCHDOG
+	tristate "Airoha EN7581 Watchdog"
+	depends on ARCH_AIROHA || COMPILE_TEST
+	select WATCHDOG_CORE
+	help
+	  Watchdog timer embedded into Airoha SoC. This will reboot your
+	  system when the timeout is reached.
+
 config ARM_SP805_WATCHDOG
 	tristate "ARM SP805 Watchdog"
 	depends on (ARM || ARM64 || COMPILE_TEST) && ARM_AMBA

drivers/watchdog/Makefile

···
 obj-$(CONFIG_ARM_SP805_WATCHDOG) += sp805_wdt.o
 obj-$(CONFIG_ARM_SBSA_WATCHDOG) += sbsa_gwdt.o
 obj-$(CONFIG_ARMADA_37XX_WATCHDOG) += armada_37xx_wdt.o
+obj-$(CONFIG_AIROHA_WATCHDOG) += airoha_wdt.o
 obj-$(CONFIG_ASM9260_WATCHDOG) += asm9260_wdt.o
 obj-$(CONFIG_AT91RM9200_WATCHDOG) += at91rm9200_wdt.o
 obj-$(CONFIG_AT91SAM9X_WATCHDOG) += at91sam9_wdt.o

drivers/watchdog/airoha_wdt.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *	Airoha Watchdog Driver
+ *
+ *	Copyright (c) 2024, AIROHA  All rights reserved.
+ *
+ *	Mayur Kumar <[e-mail]>
+ *	Christian Marangi <[e-mail]>
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/types.h>
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/math.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/watchdog.h>
+
+/* Base address of timer and watchdog registers */
+#define TIMER_CTRL			0x0
+#define   WDT_ENABLE			BIT(25)
+#define   WDT_TIMER_INTERRUPT		BIT(21)
+/* Timer3 is used as Watchdog Timer */
+#define   WDT_TIMER_ENABLE		BIT(5)
+#define WDT_TIMER_LOAD_VALUE		0x2c
+#define WDT_TIMER_CUR_VALUE		0x30
+#define  WDT_TIMER_VAL			GENMASK(31, 0)
+#define WDT_RELOAD			0x38
+#define   WDT_RLD			BIT(0)
+
+/* Airoha watchdog structure description */
+struct airoha_wdt_desc {
+	struct watchdog_device wdog_dev;
+	unsigned int wdt_freq;
+	void __iomem *base;
+};
+
+#define WDT_HEARTBEAT			24
+static int heartbeat = WDT_HEARTBEAT;
+module_param(heartbeat, int, 0);
+MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds. (default="
+		 __MODULE_STRING(WDT_HEARTBEAT) ")");
+
+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 int airoha_wdt_start(struct watchdog_device *wdog_dev)
+{
+	struct airoha_wdt_desc *airoha_wdt = watchdog_get_drvdata(wdog_dev);
+	u32 val;
+
+	val = readl(airoha_wdt->base + TIMER_CTRL);
+	val |= (WDT_TIMER_ENABLE | WDT_ENABLE | WDT_TIMER_INTERRUPT);
+	writel(val, airoha_wdt->base + TIMER_CTRL);
+	val = wdog_dev->timeout * airoha_wdt->wdt_freq;
+	writel(val, airoha_wdt->base + WDT_TIMER_LOAD_VALUE);
+
+	return 0;
+}
+
+static int airoha_wdt_stop(struct watchdog_device *wdog_dev)
+{
+	struct airoha_wdt_desc *airoha_wdt = watchdog_get_drvdata(wdog_dev);
+	u32 val;
+
+	val = readl(airoha_wdt->base + TIMER_CTRL);
+	val &= (~WDT_ENABLE & ~WDT_TIMER_ENABLE);
+	writel(val, airoha_wdt->base + TIMER_CTRL);
+
+	return 0;
+}
+
+static int airoha_wdt_ping(struct watchdog_device *wdog_dev)
+{
+	struct airoha_wdt_desc *airoha_wdt = watchdog_get_drvdata(wdog_dev);
+	u32 val;
+
+	val = readl(airoha_wdt->base + WDT_RELOAD);
+	val |= WDT_RLD;
+	writel(val, airoha_wdt->base + WDT_RELOAD);
+
+	return 0;
+}
+
+static int airoha_wdt_set_timeout(struct watchdog_device *wdog_dev, unsigned int timeout)
+{
+	wdog_dev->timeout = timeout;
+
+	if (watchdog_active(wdog_dev)) {
+		airoha_wdt_stop(wdog_dev);
+		return airoha_wdt_start(wdog_dev);
+	}
+
+	return 0;
+}
+
+static unsigned int airoha_wdt_get_timeleft(struct watchdog_device *wdog_dev)
+{
+	struct airoha_wdt_desc *airoha_wdt = watchdog_get_drvdata(wdog_dev);
+	u32 val;
+
+	val = readl(airoha_wdt->base + WDT_TIMER_CUR_VALUE);
+	return DIV_ROUND_UP(val, airoha_wdt->wdt_freq);
+}
+
+static const struct watchdog_info airoha_wdt_info = {
+	.options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
+	.identity = "Airoha Watchdog",
+};
+
+static const struct watchdog_ops airoha_wdt_ops = {
+	.owner = THIS_MODULE,
+	.start = airoha_wdt_start,
+	.stop = airoha_wdt_stop,
+	.ping = airoha_wdt_ping,
+	.set_timeout = airoha_wdt_set_timeout,
+	.get_timeleft = airoha_wdt_get_timeleft,
+};
+
+static int airoha_wdt_probe(struct platform_device *pdev)
+{
+	struct airoha_wdt_desc *airoha_wdt;
+	struct watchdog_device *wdog_dev;
+	struct device *dev = &pdev->dev;
+	struct clk *bus_clk;
+	int ret;
+
+	airoha_wdt = devm_kzalloc(dev, sizeof(*airoha_wdt), GFP_KERNEL);
+	if (!airoha_wdt)
+		return -ENOMEM;
+
+	airoha_wdt->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(airoha_wdt->base))
+		return PTR_ERR(airoha_wdt->base);
+
+	bus_clk = devm_clk_get_enabled(dev, "bus");
+	if (IS_ERR(bus_clk))
+		return dev_err_probe(dev, PTR_ERR(bus_clk),
+				     "failed to enable bus clock\n");
+
+	/* Watchdog ticks at half the bus rate */
+	airoha_wdt->wdt_freq = clk_get_rate(bus_clk) / 2;
+
+	/* Initialize struct watchdog device */
+	wdog_dev = &airoha_wdt->wdog_dev;
+	wdog_dev->timeout = heartbeat;
+	wdog_dev->info = &airoha_wdt_info;
+	wdog_dev->ops = &airoha_wdt_ops;
+	/* Bus 300MHz, watchdog 150MHz, 28 seconds */
+	wdog_dev->max_timeout = FIELD_MAX(WDT_TIMER_VAL) / airoha_wdt->wdt_freq;
+	wdog_dev->parent = dev;
+
+	watchdog_set_drvdata(wdog_dev, airoha_wdt);
+	watchdog_set_nowayout(wdog_dev, nowayout);
+	watchdog_stop_on_unregister(wdog_dev);
+
+	ret = devm_watchdog_register_device(dev, wdog_dev);
+	if (ret)
+		return ret;
+
+	platform_set_drvdata(pdev, airoha_wdt);
+	return 0;
+}
+
+static int airoha_wdt_suspend(struct device *dev)
+{
+	struct airoha_wdt_desc *airoha_wdt = dev_get_drvdata(dev);
+
+	if (watchdog_active(&airoha_wdt->wdog_dev))
+		airoha_wdt_stop(&airoha_wdt->wdog_dev);
+
+	return 0;
+}
+
+static int airoha_wdt_resume(struct device *dev)
+{
+	struct airoha_wdt_desc *airoha_wdt = dev_get_drvdata(dev);
+
+	if (watchdog_active(&airoha_wdt->wdog_dev)) {
+		airoha_wdt_start(&airoha_wdt->wdog_dev);
+		airoha_wdt_ping(&airoha_wdt->wdog_dev);
+	}
+	return 0;
+}
+
+static const struct of_device_id airoha_wdt_of_match[] = {
+	{ .compatible = "airoha,en7581-wdt", },
+	{ },
+};
+
+MODULE_DEVICE_TABLE(of, airoha_wdt_of_match);
+
+static DEFINE_SIMPLE_DEV_PM_OPS(airoha_wdt_pm_ops, airoha_wdt_suspend, airoha_wdt_resume);
+
+static struct platform_driver airoha_wdt_driver = {
+	.probe = airoha_wdt_probe,
+	.driver = {
+		.name = "airoha-wdt",
+		.pm = pm_sleep_ptr(&airoha_wdt_pm_ops),
+		.of_match_table = airoha_wdt_of_match,
+	},
+};
+
+module_platform_driver(airoha_wdt_driver);
+
+MODULE_AUTHOR("Mayur Kumar <[e-mail]>");
+MODULE_AUTHOR("Christian Marangi <[e-mail]>");
+MODULE_DESCRIPTION("Airoha EN7581 Watchdog Driver");
+MODULE_LICENSE("GPL");