watchdog: add support for the Synopsys DesignWare WDT

The Synopsys DesignWare watchdog is found in several ARM based systems
and provides a choice of 16 timeout periods depending on the clock
input.  The watchdog cannot be disabled once started.

Signed-off-by: Jamie Iles <jamie@jamieiles.com>
Acked-by: Viresh Kumar <viresh.kumar@st.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/Kconfig

@@ -186,6 +186,15 @@ config SA1100_WATCHDOG
 	  To compile this driver as a module, choose M here: the
 	  module will be called sa1100_wdt.
 
+config DW_WATCHDOG
+	tristate "Synopsys DesignWare watchdog"
+	depends on ARM && HAVE_CLK
+	help
+	  Say Y here if to include support for the Synopsys DesignWare
+	  watchdog timer found in many ARM chips.
+	  To compile this driver as a module, choose M here: the
+	  module will be called dw_wdt.
+
 config MPCORE_WATCHDOG
 	tristate "MPcore watchdog"
 	depends on HAVE_ARM_TWD

drivers/watchdog/Makefile

@@ -37,6 +37,7 @@ obj-$(CONFIG_IXP4XX_WATCHDOG) += ixp4xx_wdt.o
 obj-$(CONFIG_KS8695_WATCHDOG) += ks8695_wdt.o
 obj-$(CONFIG_S3C2410_WATCHDOG) += s3c2410_wdt.o
 obj-$(CONFIG_SA1100_WATCHDOG) += sa1100_wdt.o
+obj-$(CONFIG_DW_WATCHDOG) += dw_wdt.o
 obj-$(CONFIG_MPCORE_WATCHDOG) += mpcore_wdt.o
 obj-$(CONFIG_EP93XX_WATCHDOG) += ep93xx_wdt.o
 obj-$(CONFIG_PNX4008_WATCHDOG) += pnx4008_wdt.o

drivers/watchdog/dw_wdt.c

@@ -0,0 +1,376 @@
+/*
+ * Copyright 2010-2011 Picochip Ltd., Jamie Iles
+ * http://www.picochip.com
+ *
+ * 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.
+ *
+ * This file implements a driver for the Synopsys DesignWare watchdog device
+ * in the many ARM subsystems. The watchdog has 16 different timeout periods
+ * and these are a function of the input clock frequency.
+ *
+ * The DesignWare watchdog cannot be stopped once it has been started so we
+ * use a software timer to implement a ping that will keep the watchdog alive.
+ * If we receive an expected close for the watchdog then we keep the timer
+ * running, otherwise the timer is stopped and the watchdog will expire.
+ */
+#define pr_fmt(fmt) "dw_wdt: " fmt
+
+#include <linux/bitops.h>
+#include <linux/clk.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/fs.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/pm.h>
+#include <linux/platform_device.h>
+#include <linux/spinlock.h>
+#include <linux/timer.h>
+#include <linux/uaccess.h>
+#include <linux/watchdog.h>
+
+#define WDOG_CONTROL_REG_OFFSET		    0x00
+#define WDOG_CONTROL_REG_WDT_EN_MASK	    0x01
+#define WDOG_TIMEOUT_RANGE_REG_OFFSET	    0x04
+#define WDOG_CURRENT_COUNT_REG_OFFSET	    0x08
+#define WDOG_COUNTER_RESTART_REG_OFFSET     0x0c
+#define WDOG_COUNTER_RESTART_KICK_VALUE	    0x76
+
+/* The maximum TOP (timeout period) value that can be set in the watchdog. */
+#define DW_WDT_MAX_TOP		15
+
+static int nowayout = WATCHDOG_NOWAYOUT;
+module_param(nowayout, int, 0);
+MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
+		 "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+
+#define WDT_TIMEOUT		(HZ / 2)
+
+static struct {
+	spinlock_t		lock;
+	void __iomem		*regs;
+	struct clk		*clk;
+	unsigned long		in_use;
+	unsigned long		next_heartbeat;
+	struct timer_list	timer;
+	int			expect_close;
+} dw_wdt;
+
+static inline int dw_wdt_is_enabled(void)
+{
+	return readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET) &
+		WDOG_CONTROL_REG_WDT_EN_MASK;
+}
+
+static inline int dw_wdt_top_in_seconds(unsigned top)
+{
+	/*
+	 * There are 16 possible timeout values in 0..15 where the number of
+	 * cycles is 2 ^ (16 + i) and the watchdog counts down.
+	 */
+	return (1 << (16 + top)) / clk_get_rate(dw_wdt.clk);
+}
+
+static int dw_wdt_get_top(void)
+{
+	int top = readl(dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET) & 0xF;
+
+	return dw_wdt_top_in_seconds(top);
+}
+
+static inline void dw_wdt_set_next_heartbeat(void)
+{
+	dw_wdt.next_heartbeat = jiffies + dw_wdt_get_top() * HZ;
+}
+
+static int dw_wdt_set_top(unsigned top_s)
+{
+	int i, top_val = DW_WDT_MAX_TOP;
+
+	/*
+	 * Iterate over the timeout values until we find the closest match. We
+	 * always look for >=.
+	 */
+	for (i = 0; i <= DW_WDT_MAX_TOP; ++i)
+		if (dw_wdt_top_in_seconds(i) >= top_s) {
+			top_val = i;
+			break;
+		}
+
+	/* Set the new value in the watchdog. */
+	writel(top_val, dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);
+
+	dw_wdt_set_next_heartbeat();
+
+	return dw_wdt_top_in_seconds(top_val);
+}
+
+static void dw_wdt_keepalive(void)
+{
+	writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
+	       WDOG_COUNTER_RESTART_REG_OFFSET);
+}
+
+static void dw_wdt_ping(unsigned long data)
+{
+	if (time_before(jiffies, dw_wdt.next_heartbeat) ||
+	    (!nowayout && !dw_wdt.in_use)) {
+		dw_wdt_keepalive();
+		mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
+	} else
+		pr_crit("keepalive missed, machine will reset\n");
+}
+
+static int dw_wdt_open(struct inode *inode, struct file *filp)
+{
+	if (test_and_set_bit(0, &dw_wdt.in_use))
+		return -EBUSY;
+
+	/* Make sure we don't get unloaded. */
+	__module_get(THIS_MODULE);
+
+	spin_lock(&dw_wdt.lock);
+	if (!dw_wdt_is_enabled()) {
+		/*
+		 * The watchdog is not currently enabled. Set the timeout to
+		 * the maximum and then start it.
+		 */
+		dw_wdt_set_top(DW_WDT_MAX_TOP);
+		writel(WDOG_CONTROL_REG_WDT_EN_MASK,
+		       dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
+	}
+
+	dw_wdt_set_next_heartbeat();
+
+	spin_unlock(&dw_wdt.lock);
+
+	return nonseekable_open(inode, filp);
+}
+
+ssize_t dw_wdt_write(struct file *filp, const char __user *buf, size_t len,
+		     loff_t *offset)
+{
+	if (!len)
+		return 0;
+
+	if (!nowayout) {
+		size_t i;
+
+		dw_wdt.expect_close = 0;
+
+		for (i = 0; i < len; ++i) {
+			char c;
+
+			if (get_user(c, buf + i))
+				return -EFAULT;
+
+			if (c == 'V') {
+				dw_wdt.expect_close = 1;
+				break;
+			}
+		}
+	}
+
+	dw_wdt_set_next_heartbeat();
+	mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
+
+	return len;
+}
+
+static u32 dw_wdt_time_left(void)
+{
+	return readl(dw_wdt.regs + WDOG_CURRENT_COUNT_REG_OFFSET) /
+		clk_get_rate(dw_wdt.clk);
+}
+
+static const struct watchdog_info dw_wdt_ident = {
+	.options	= WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
+			  WDIOF_MAGICCLOSE,
+	.identity	= "Synopsys DesignWare Watchdog",
+};
+
+static long dw_wdt_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+{
+	unsigned long val;
+	int timeout;
+
+	switch (cmd) {
+	case WDIOC_GETSUPPORT:
+		return copy_to_user((struct watchdog_info *)arg, &dw_wdt_ident,
+				    sizeof(dw_wdt_ident)) ? -EFAULT : 0;
+
+	case WDIOC_GETSTATUS:
+	case WDIOC_GETBOOTSTATUS:
+		return put_user(0, (int *)arg);
+
+	case WDIOC_KEEPALIVE:
+		dw_wdt_set_next_heartbeat();
+		return 0;
+
+	case WDIOC_SETTIMEOUT:
+		if (get_user(val, (int __user *)arg))
+			return -EFAULT;
+		timeout = dw_wdt_set_top(val);
+		return put_user(timeout , (int __user *)arg);
+
+	case WDIOC_GETTIMEOUT:
+		return put_user(dw_wdt_get_top(), (int __user *)arg);
+
+	case WDIOC_GETTIMELEFT:
+		/* Get the time left until expiry. */
+		if (get_user(val, (int __user *)arg))
+			return -EFAULT;
+		return put_user(dw_wdt_time_left(), (int __user *)arg);
+
+	default:
+		return -ENOTTY;
+	}
+}
+
+static int dw_wdt_release(struct inode *inode, struct file *filp)
+{
+	clear_bit(0, &dw_wdt.in_use);
+
+	if (!dw_wdt.expect_close) {
+		del_timer(&dw_wdt.timer);
+
+		if (!nowayout)
+			pr_crit("unexpected close, system will reboot soon\n");
+		else
+			pr_crit("watchdog cannot be disabled, system will reboot soon\n");
+	}
+
+	dw_wdt.expect_close = 0;
+
+	return 0;
+}
+
+#ifdef CONFIG_PM
+static int dw_wdt_suspend(struct device *dev)
+{
+	clk_disable(dw_wdt.clk);
+
+	return 0;
+}
+
+static int dw_wdt_resume(struct device *dev)
+{
+	int err = clk_enable(dw_wdt.clk);
+
+	if (err)
+		return err;
+
+	dw_wdt_keepalive();
+
+	return 0;
+}
+
+static const struct dev_pm_ops dw_wdt_pm_ops = {
+	.suspend	= dw_wdt_suspend,
+	.resume		= dw_wdt_resume,
+};
+#endif /* CONFIG_PM */
+
+static const struct file_operations wdt_fops = {
+	.owner		= THIS_MODULE,
+	.llseek		= no_llseek,
+	.open		= dw_wdt_open,
+	.write		= dw_wdt_write,
+	.unlocked_ioctl	= dw_wdt_ioctl,
+	.release	= dw_wdt_release
+};
+
+static struct miscdevice dw_wdt_miscdev = {
+	.fops		= &wdt_fops,
+	.name		= "watchdog",
+	.minor		= WATCHDOG_MINOR,
+};
+
+static int __devinit dw_wdt_drv_probe(struct platform_device *pdev)
+{
+	int ret;
+	struct resource *mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+
+	if (!mem)
+		return -EINVAL;
+
+	if (!devm_request_mem_region(&pdev->dev, mem->start, resource_size(mem),
+				     "dw_wdt"))
+		return -ENOMEM;
+
+	dw_wdt.regs = devm_ioremap(&pdev->dev, mem->start, resource_size(mem));
+	if (!dw_wdt.regs)
+		return -ENOMEM;
+
+	dw_wdt.clk = clk_get(&pdev->dev, NULL);
+	if (IS_ERR(dw_wdt.clk))
+		return PTR_ERR(dw_wdt.clk);
+
+	ret = clk_enable(dw_wdt.clk);
+	if (ret)
+		goto out_put_clk;
+
+	spin_lock_init(&dw_wdt.lock);
+
+	ret = misc_register(&dw_wdt_miscdev);
+	if (ret)
+		goto out_disable_clk;
+
+	dw_wdt_set_next_heartbeat();
+	setup_timer(&dw_wdt.timer, dw_wdt_ping, 0);
+	mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
+
+	return 0;
+
+out_disable_clk:
+	clk_disable(dw_wdt.clk);
+out_put_clk:
+	clk_put(dw_wdt.clk);
+
+	return ret;
+}
+
+static int __devexit dw_wdt_drv_remove(struct platform_device *pdev)
+{
+	misc_deregister(&dw_wdt_miscdev);
+
+	clk_disable(dw_wdt.clk);
+	clk_put(dw_wdt.clk);
+
+	return 0;
+}
+
+static struct platform_driver dw_wdt_driver = {
+	.probe		= dw_wdt_drv_probe,
+	.remove		= __devexit_p(dw_wdt_drv_remove),
+	.driver		= {
+		.name	= "dw_wdt",
+		.owner	= THIS_MODULE,
+#ifdef CONFIG_PM
+		.pm	= &dw_wdt_pm_ops,
+#endif /* CONFIG_PM */
+	},
+};
+
+static int __init dw_wdt_watchdog_init(void)
+{
+	return platform_driver_register(&dw_wdt_driver);
+}
+module_init(dw_wdt_watchdog_init);
+
+static void __exit dw_wdt_watchdog_exit(void)
+{
+	platform_driver_unregister(&dw_wdt_driver);
+}
+module_exit(dw_wdt_watchdog_exit);
+
+MODULE_AUTHOR("Jamie Iles");
+MODULE_DESCRIPTION("Synopsys DesignWare Watchdog Driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);