watchdog: Add Cadence WDT driver

Add Cadence WDT driver. This is used by Xilinx Zynq.

Signed-off-by: Harini Katakam <[e-mail]>
Reviewed-by: Guenter Roeck <[e-mail]>
Signed-off-by: Wim Van Sebroeck <[e-mail]>

drivers/watchdog/Kconfig

···
 	  Watchdog timer embedded into AT91SAM9X and AT91CAP9 chips. This will
 	  reboot your system when the timeout is reached.
 
+config CADENCE_WATCHDOG
+	tristate "Cadence Watchdog Timer"
+	depends on ARM
+	select WATCHDOG_CORE
+	help
+	  Say Y here if you want to include support for the watchdog
+	  timer in the Xilinx Zynq.
+
 config 21285_WATCHDOG
 	tristate "DC21285 watchdog"
 	depends on FOOTBRIDGE

drivers/watchdog/Makefile

···
 obj-$(CONFIG_ARM_SP805_WATCHDOG) += sp805_wdt.o
 obj-$(CONFIG_AT91RM9200_WATCHDOG) += at91rm9200_wdt.o
 obj-$(CONFIG_AT91SAM9X_WATCHDOG) += at91sam9_wdt.o
+obj-$(CONFIG_CADENCE_WATCHDOG) += cadence_wdt.o
 obj-$(CONFIG_OMAP_WATCHDOG) += omap_wdt.o
 obj-$(CONFIG_TWL4030_WATCHDOG) += twl4030_wdt.o
 obj-$(CONFIG_21285_WATCHDOG) += wdt285.o

drivers/watchdog/cadence_wdt.c

···
+/*
+ * Cadence WDT driver - Used by Xilinx Zynq
+ *
+ * Copyright (C) 2010 - 2014 Xilinx, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/clk.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/reboot.h>
+#include <linux/watchdog.h>
+
+#define CDNS_WDT_DEFAULT_TIMEOUT	10
+/* Supports 1 - 516 sec */
+#define CDNS_WDT_MIN_TIMEOUT	1
+#define CDNS_WDT_MAX_TIMEOUT	516
+
+/* Restart key */
+#define CDNS_WDT_RESTART_KEY 0x00001999
+
+/* Counter register access key */
+#define CDNS_WDT_REGISTER_ACCESS_KEY 0x00920000
+
+/* Counter value divisor */
+#define CDNS_WDT_COUNTER_VALUE_DIVISOR 0x1000
+
+/* Clock prescaler value and selection */
+#define CDNS_WDT_PRESCALE_64	64
+#define CDNS_WDT_PRESCALE_512	512
+#define CDNS_WDT_PRESCALE_4096	4096
+#define CDNS_WDT_PRESCALE_SELECT_64	1
+#define CDNS_WDT_PRESCALE_SELECT_512	2
+#define CDNS_WDT_PRESCALE_SELECT_4096	3
+
+/* Input clock frequency */
+#define CDNS_WDT_CLK_10MHZ	10000000
+#define CDNS_WDT_CLK_75MHZ	75000000
+
+/* Counter maximum value */
+#define CDNS_WDT_COUNTER_MAX 0xFFF
+
+static int wdt_timeout = CDNS_WDT_DEFAULT_TIMEOUT;
+static int nowayout = WATCHDOG_NOWAYOUT;
+
+module_param(wdt_timeout, int, 0);
+MODULE_PARM_DESC(wdt_timeout,
+		 "Watchdog time in seconds. (default="
+		 __MODULE_STRING(CDNS_WDT_DEFAULT_TIMEOUT) ")");
+
+module_param(nowayout, int, 0);
+MODULE_PARM_DESC(nowayout,
+		 "Watchdog cannot be stopped once started (default="
+		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+
+/**
+ * struct cdns_wdt - Watchdog device structure
+ * @regs: baseaddress of device
+ * @rst: reset flag
+ * @clk: struct clk * of a clock source
+ * @prescaler: for saving prescaler value
+ * @ctrl_clksel: counter clock prescaler selection
+ * @io_lock: spinlock for IO register access
+ * @cdns_wdt_device: watchdog device structure
+ * @cdns_wdt_notifier: notifier structure
+ *
+ * Structure containing parameters specific to cadence watchdog.
+ */
+struct cdns_wdt {
+	void __iomem		*regs;
+	bool			rst;
+	struct clk		*clk;
+	u32			prescaler;
+	u32			ctrl_clksel;
+	spinlock_t		io_lock;
+	struct watchdog_device	cdns_wdt_device;
+	struct notifier_block	cdns_wdt_notifier;
+};
+
+/* Write access to Registers */
+static inline void cdns_wdt_writereg(struct cdns_wdt *wdt, u32 offset, u32 val)
+{
+	writel_relaxed(val, wdt->regs + offset);
+}
+
+/*************************Register Map**************************************/
+
+/* Register Offsets for the WDT */
+#define CDNS_WDT_ZMR_OFFSET	0x0	/* Zero Mode Register */
+#define CDNS_WDT_CCR_OFFSET	0x4	/* Counter Control Register */
+#define CDNS_WDT_RESTART_OFFSET	0x8	/* Restart Register */
+#define CDNS_WDT_SR_OFFSET	0xC	/* Status Register */
+
+/*
+ * Zero Mode Register - This register controls how the time out is indicated
+ * and also contains the access code to allow writes to the register (0xABC).
+ */
+#define CDNS_WDT_ZMR_WDEN_MASK	0x00000001 /* Enable the WDT */
+#define CDNS_WDT_ZMR_RSTEN_MASK	0x00000002 /* Enable the reset output */
+#define CDNS_WDT_ZMR_IRQEN_MASK	0x00000004 /* Enable IRQ output */
+#define CDNS_WDT_ZMR_RSTLEN_16	0x00000030 /* Reset pulse of 16 pclk cycles */
+#define CDNS_WDT_ZMR_ZKEY_VAL	0x00ABC000 /* Access key, 0xABC << 12 */
+/*
+ * Counter Control register - This register controls how fast the timer runs
+ * and the reset value and also contains the access code to allow writes to
+ * the register.
+ */
+#define CDNS_WDT_CCR_CRV_MASK	0x00003FFC /* Counter reset value */
+
+/**
+ * cdns_wdt_stop - Stop the watchdog.
+ *
+ * @wdd: watchdog device
+ *
+ * Read the contents of the ZMR register, clear the WDEN bit
+ * in the register and set the access key for successful write.
+ *
+ * Return: always 0
+ */
+static int cdns_wdt_stop(struct watchdog_device *wdd)
+{
+	struct cdns_wdt *wdt = watchdog_get_drvdata(wdd);
+
+	spin_lock(&wdt->io_lock);
+	cdns_wdt_writereg(wdt, CDNS_WDT_ZMR_OFFSET,
+			  CDNS_WDT_ZMR_ZKEY_VAL & (~CDNS_WDT_ZMR_WDEN_MASK));
+	spin_unlock(&wdt->io_lock);
+
+	return 0;
+}
+
+/**
+ * cdns_wdt_reload - Reload the watchdog timer (i.e. pat the watchdog).
+ *
+ * @wdd: watchdog device
+ *
+ * Write the restart key value (0x00001999) to the restart register.
+ *
+ * Return: always 0
+ */
+static int cdns_wdt_reload(struct watchdog_device *wdd)
+{
+	struct cdns_wdt *wdt = watchdog_get_drvdata(wdd);
+
+	spin_lock(&wdt->io_lock);
+	cdns_wdt_writereg(wdt, CDNS_WDT_RESTART_OFFSET,
+			  CDNS_WDT_RESTART_KEY);
+	spin_unlock(&wdt->io_lock);
+
+	return 0;
+}
+
+/**
+ * cdns_wdt_start - Enable and start the watchdog.
+ *
+ * @wdd: watchdog device
+ *
+ * The counter value is calculated according to the formula:
+ *		calculated count = (timeout * clock) / prescaler + 1.
+ * The calculated count is divided by 0x1000 to obtain the field value
+ * to write to counter control register.
+ * Clears the contents of prescaler and counter reset value. Sets the
+ * prescaler to 4096 and the calculated count and access key
+ * to write to CCR Register.
+ * Sets the WDT (WDEN bit) and either the Reset signal(RSTEN bit)
+ * or Interrupt signal(IRQEN) with a specified cycles and the access
+ * key to write to ZMR Register.
+ *
+ * Return: always 0
+ */
+static int cdns_wdt_start(struct watchdog_device *wdd)
+{
+	struct cdns_wdt *wdt = watchdog_get_drvdata(wdd);
+	unsigned int data = 0;
+	unsigned short count;
+	unsigned long clock_f = clk_get_rate(wdt->clk);
+
+	/*
+	 * Counter value divisor to obtain the value of
+	 * counter reset to be written to control register.
+	 */
+	count = (wdd->timeout * (clock_f / wdt->prescaler)) /
+		 CDNS_WDT_COUNTER_VALUE_DIVISOR + 1;
+
+	if (count > CDNS_WDT_COUNTER_MAX)
+		count = CDNS_WDT_COUNTER_MAX;
+
+	spin_lock(&wdt->io_lock);
+	cdns_wdt_writereg(wdt, CDNS_WDT_ZMR_OFFSET,
+			  CDNS_WDT_ZMR_ZKEY_VAL);
+
+	count = (count << 2) & CDNS_WDT_CCR_CRV_MASK;
+
+	/* Write counter access key first to be able write to register */
+	data = count | CDNS_WDT_REGISTER_ACCESS_KEY | wdt->ctrl_clksel;
+	cdns_wdt_writereg(wdt, CDNS_WDT_CCR_OFFSET, data);
+	data = CDNS_WDT_ZMR_WDEN_MASK | CDNS_WDT_ZMR_RSTLEN_16 |
+	       CDNS_WDT_ZMR_ZKEY_VAL;
+
+	/* Reset on timeout if specified in device tree. */
+	if (wdt->rst) {
+		data |= CDNS_WDT_ZMR_RSTEN_MASK;
+		data &= ~CDNS_WDT_ZMR_IRQEN_MASK;
+	} else {
+		data &= ~CDNS_WDT_ZMR_RSTEN_MASK;
+		data |= CDNS_WDT_ZMR_IRQEN_MASK;
+	}
+	cdns_wdt_writereg(wdt, CDNS_WDT_ZMR_OFFSET, data);
+	cdns_wdt_writereg(wdt, CDNS_WDT_RESTART_OFFSET,
+			  CDNS_WDT_RESTART_KEY);
+	spin_unlock(&wdt->io_lock);
+
+	return 0;
+}
+
+/**
+ * cdns_wdt_settimeout - Set a new timeout value for the watchdog device.
+ *
+ * @wdd: watchdog device
+ * @new_time: new timeout value that needs to be set
+ * Return: 0 on success
+ *
+ * Update the watchdog_device timeout with new value which is used when
+ * cdns_wdt_start is called.
+ */
+static int cdns_wdt_settimeout(struct watchdog_device *wdd,
+			       unsigned int new_time)
+{
+	wdd->timeout = new_time;
+
+	return cdns_wdt_start(wdd);
+}
+
+/**
+ * cdns_wdt_irq_handler - Notifies of watchdog timeout.
+ *
+ * @irq: interrupt number
+ * @dev_id: pointer to a platform device structure
+ * Return: IRQ_HANDLED
+ *
+ * The handler is invoked when the watchdog times out and a
+ * reset on timeout has not been enabled.
+ */
+static irqreturn_t cdns_wdt_irq_handler(int irq, void *dev_id)
+{
+	struct platform_device *pdev = dev_id;
+
+	dev_info(&pdev->dev,
+		 "Watchdog timed out. Internal reset not enabled\n");
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * Info structure used to indicate the features supported by the device
+ * to the upper layers. This is defined in watchdog.h header file.
+ */
+static struct watchdog_info cdns_wdt_info = {
+	.identity	= "cdns_wdt watchdog",
+	.options	= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
+			  WDIOF_MAGICCLOSE,
+};
+
+/* Watchdog Core Ops */
+static struct watchdog_ops cdns_wdt_ops = {
+	.owner = THIS_MODULE,
+	.start = cdns_wdt_start,
+	.stop = cdns_wdt_stop,
+	.ping = cdns_wdt_reload,
+	.set_timeout = cdns_wdt_settimeout,
+};
+
+/**
+ * cdns_wdt_notify_sys - Notifier for reboot or shutdown.
+ *
+ * @this: handle to notifier block
+ * @code: turn off indicator
+ * @unused: unused
+ * Return: NOTIFY_DONE
+ *
+ * This notifier is invoked whenever the system reboot or shutdown occur
+ * because we need to disable the WDT before system goes down as WDT might
+ * reset on the next boot.
+ */
+static int cdns_wdt_notify_sys(struct notifier_block *this, unsigned long code,
+			       void *unused)
+{
+	struct cdns_wdt *wdt = container_of(this, struct cdns_wdt,
+					    cdns_wdt_notifier);
+	if (code == SYS_DOWN || code == SYS_HALT)
+		cdns_wdt_stop(&wdt->cdns_wdt_device);
+
+	return NOTIFY_DONE;
+}
+
+/************************Platform Operations*****************************/
+/**
+ * cdns_wdt_probe - Probe call for the device.
+ *
+ * @pdev: handle to the platform device structure.
+ * Return: 0 on success, negative error otherwise.
+ *
+ * It does all the memory allocation and registration for the device.
+ */
+static int cdns_wdt_probe(struct platform_device *pdev)
+{
+	struct resource *res;
+	int ret, irq;
+	unsigned long clock_f;
+	struct cdns_wdt *wdt;
+	struct watchdog_device *cdns_wdt_device;
+
+	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
+	if (!wdt)
+		return -ENOMEM;
+
+	cdns_wdt_device = &wdt->cdns_wdt_device;
+	cdns_wdt_device->info = &cdns_wdt_info;
+	cdns_wdt_device->ops = &cdns_wdt_ops;
+	cdns_wdt_device->timeout = CDNS_WDT_DEFAULT_TIMEOUT;
+	cdns_wdt_device->min_timeout = CDNS_WDT_MIN_TIMEOUT;
+	cdns_wdt_device->max_timeout = CDNS_WDT_MAX_TIMEOUT;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	wdt->regs = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(wdt->regs))
+		return PTR_ERR(wdt->regs);
+
+	/* Register the interrupt */
+	wdt->rst = of_property_read_bool(pdev->dev.of_node, "reset-on-timeout");
+	irq = platform_get_irq(pdev, 0);
+	if (!wdt->rst && irq >= 0) {
+		ret = devm_request_irq(&pdev->dev, irq, cdns_wdt_irq_handler, 0,
+				       pdev->name, pdev);
+		if (ret) {
+			dev_err(&pdev->dev,
+				"cannot register interrupt handler err=%d\n",
+				ret);
+			return ret;
+		}
+	}
+
+	/* Initialize the members of cdns_wdt structure */
+	cdns_wdt_device->parent = &pdev->dev;
+
+	ret = watchdog_init_timeout(cdns_wdt_device, wdt_timeout, &pdev->dev);
+	if (ret) {
+		dev_err(&pdev->dev, "unable to set timeout value\n");
+		return ret;
+	}
+
+	watchdog_set_nowayout(cdns_wdt_device, nowayout);
+	watchdog_set_drvdata(cdns_wdt_device, wdt);
+
+	wdt->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(wdt->clk)) {
+		dev_err(&pdev->dev, "input clock not found\n");
+		ret = PTR_ERR(wdt->clk);
+		return ret;
+	}
+
+	ret = clk_prepare_enable(wdt->clk);
+	if (ret) {
+		dev_err(&pdev->dev, "unable to enable clock\n");
+		return ret;
+	}
+
+	clock_f = clk_get_rate(wdt->clk);
+	if (clock_f <= CDNS_WDT_CLK_75MHZ) {
+		wdt->prescaler = CDNS_WDT_PRESCALE_512;
+		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_512;
+	} else {
+		wdt->prescaler = CDNS_WDT_PRESCALE_4096;
+		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_4096;
+	}
+
+	spin_lock_init(&wdt->io_lock);
+
+	wdt->cdns_wdt_notifier.notifier_call = &cdns_wdt_notify_sys;
+	ret = register_reboot_notifier(&wdt->cdns_wdt_notifier);
+	if (ret != 0) {
+		dev_err(&pdev->dev, "cannot register reboot notifier err=%d)\n",
+			ret);
+		goto err_clk_disable;
+	}
+
+	ret = watchdog_register_device(cdns_wdt_device);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to register wdt device\n");
+		goto err_clk_disable;
+	}
+	platform_set_drvdata(pdev, wdt);
+
+	dev_dbg(&pdev->dev, "Xilinx Watchdog Timer at %p with timeout %ds%s\n",
+		 wdt->regs, cdns_wdt_device->timeout,
+		 nowayout ? ", nowayout" : "");
+
+	return 0;
+
+err_clk_disable:
+	clk_disable_unprepare(wdt->clk);
+
+	return ret;
+}
+
+/**
+ * cdns_wdt_remove - Probe call for the device.
+ *
+ * @pdev: handle to the platform device structure.
+ * Return: 0 on success, otherwise negative error.
+ *
+ * Unregister the device after releasing the resources.
+ */
+static int cdns_wdt_remove(struct platform_device *pdev)
+{
+	struct cdns_wdt *wdt = platform_get_drvdata(pdev);
+
+	cdns_wdt_stop(&wdt->cdns_wdt_device);
+	watchdog_unregister_device(&wdt->cdns_wdt_device);
+	unregister_reboot_notifier(&wdt->cdns_wdt_notifier);
+	clk_disable_unprepare(wdt->clk);
+
+	return 0;
+}
+
+/**
+ * cdns_wdt_shutdown - Stop the device.
+ *
+ * @pdev: handle to the platform structure.
+ *
+ */
+static void cdns_wdt_shutdown(struct platform_device *pdev)
+{
+	struct cdns_wdt *wdt = platform_get_drvdata(pdev);
+
+	cdns_wdt_stop(&wdt->cdns_wdt_device);
+	clk_disable_unprepare(wdt->clk);
+}
+
+/**
+ * cdns_wdt_suspend - Stop the device.
+ *
+ * @dev: handle to the device structure.
+ * Return: 0 always.
+ */
+static int __maybe_unused cdns_wdt_suspend(struct device *dev)
+{
+	struct platform_device *pdev = container_of(dev,
+			struct platform_device, dev);
+	struct cdns_wdt *wdt = platform_get_drvdata(pdev);
+
+	cdns_wdt_stop(&wdt->cdns_wdt_device);
+	clk_disable_unprepare(wdt->clk);
+
+	return 0;
+}
+
+/**
+ * cdns_wdt_resume - Resume the device.
+ *
+ * @dev: handle to the device structure.
+ * Return: 0 on success, errno otherwise.
+ */
+static int __maybe_unused cdns_wdt_resume(struct device *dev)
+{
+	int ret;
+	struct platform_device *pdev = container_of(dev,
+			struct platform_device, dev);
+	struct cdns_wdt *wdt = platform_get_drvdata(pdev);
+
+	ret = clk_prepare_enable(wdt->clk);
+	if (ret) {
+		dev_err(dev, "unable to enable clock\n");
+		return ret;
+	}
+	cdns_wdt_start(&wdt->cdns_wdt_device);
+
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(cdns_wdt_pm_ops, cdns_wdt_suspend, cdns_wdt_resume);
+
+static struct of_device_id cdns_wdt_of_match[] = {
+	{ .compatible = "cdns,wdt-r1p2", },
+	{ /* end of table */ }
+};
+MODULE_DEVICE_TABLE(of, cdns_wdt_of_match);
+
+/* Driver Structure */
+static struct platform_driver cdns_wdt_driver = {
+	.probe		= cdns_wdt_probe,
+	.remove		= cdns_wdt_remove,
+	.shutdown	= cdns_wdt_shutdown,
+	.driver		= {
+		.name	= "cdns-wdt",
+		.owner	= THIS_MODULE,
+		.of_match_table = cdns_wdt_of_match,
+		.pm	= &cdns_wdt_pm_ops,
+	},
+};
+
+module_platform_driver(cdns_wdt_driver);
+
+MODULE_AUTHOR("Xilinx, Inc.");
+MODULE_DESCRIPTION("Watchdog driver for Cadence WDT");
+MODULE_LICENSE("GPL");