2 * Copyright 2010-2011 Picochip Ltd., Jamie Iles
3 * http://www.picochip.com
5 * This program is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU General Public License
7 * as published by the Free Software Foundation; either version
8 * 2 of the License, or (at your option) any later version.
10 * This file implements a driver for the Synopsys DesignWare watchdog device
11 * in the many subsystems. The watchdog has 16 different timeout periods
12 * and these are a function of the input clock frequency.
14 * The DesignWare watchdog cannot be stopped once it has been started so we
15 * use a software timer to implement a ping that will keep the watchdog alive.
16 * If we receive an expected close for the watchdog then we keep the timer
17 * running, otherwise the timer is stopped and the watchdog will expire.
20 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
22 #include <linux/bitops.h>
23 #include <linux/clk.h>
24 #include <linux/delay.h>
25 #include <linux/device.h>
26 #include <linux/err.h>
29 #include <linux/kernel.h>
30 #include <linux/miscdevice.h>
31 #include <linux/module.h>
32 #include <linux/moduleparam.h>
33 #include <linux/notifier.h>
36 #include <linux/platform_device.h>
37 #include <linux/reboot.h>
38 #include <linux/timer.h>
39 #include <linux/uaccess.h>
40 #include <linux/watchdog.h>
42 #define WDOG_CONTROL_REG_OFFSET 0x00
43 #define WDOG_CONTROL_REG_WDT_EN_MASK 0x01
44 #define WDOG_TIMEOUT_RANGE_REG_OFFSET 0x04
45 #define WDOG_TIMEOUT_RANGE_TOPINIT_SHIFT 4
46 #define WDOG_CURRENT_COUNT_REG_OFFSET 0x08
47 #define WDOG_COUNTER_RESTART_REG_OFFSET 0x0c
48 #define WDOG_COUNTER_RESTART_KICK_VALUE 0x76
50 /* The maximum TOP (timeout period) value that can be set in the watchdog. */
51 #define DW_WDT_MAX_TOP 15
53 #define DW_WDT_DEFAULT_SECONDS 30
55 static bool nowayout = WATCHDOG_NOWAYOUT;
56 module_param(nowayout, bool, 0);
57 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
58 "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
60 #define WDT_TIMEOUT (HZ / 2)
66 unsigned long next_heartbeat;
67 struct timer_list timer;
69 struct notifier_block restart_handler;
72 static inline int dw_wdt_is_enabled(void)
74 return readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET) &
75 WDOG_CONTROL_REG_WDT_EN_MASK;
78 static inline int dw_wdt_top_in_seconds(unsigned top)
81 * There are 16 possible timeout values in 0..15 where the number of
82 * cycles is 2 ^ (16 + i) and the watchdog counts down.
84 return (1 << (16 + top)) / clk_get_rate(dw_wdt.clk);
87 static int dw_wdt_get_top(void)
89 int top = readl(dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET) & 0xF;
91 return dw_wdt_top_in_seconds(top);
94 static inline void dw_wdt_set_next_heartbeat(void)
96 dw_wdt.next_heartbeat = jiffies + dw_wdt_get_top() * HZ;
99 static void dw_wdt_keepalive(void)
101 writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
102 WDOG_COUNTER_RESTART_REG_OFFSET);
105 static int dw_wdt_set_top(unsigned top_s)
107 int i, top_val = DW_WDT_MAX_TOP;
110 * Iterate over the timeout values until we find the closest match. We
111 * always look for >=.
113 for (i = 0; i <= DW_WDT_MAX_TOP; ++i)
114 if (dw_wdt_top_in_seconds(i) >= top_s) {
120 * Set the new value in the watchdog. Some versions of dw_wdt
121 * have have TOPINIT in the TIMEOUT_RANGE register (as per
122 * CP_WDT_DUAL_TOP in WDT_COMP_PARAMS_1). On those we
123 * effectively get a pat of the watchdog right here.
125 writel(top_val | top_val << WDOG_TIMEOUT_RANGE_TOPINIT_SHIFT,
126 dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);
129 * Add an explicit pat to handle versions of the watchdog that
130 * don't have TOPINIT. This won't hurt on versions that have
135 dw_wdt_set_next_heartbeat();
137 return dw_wdt_top_in_seconds(top_val);
140 static int dw_wdt_restart_handle(struct notifier_block *this,
141 unsigned long mode, void *cmd)
145 writel(0, dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);
146 val = readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
147 if (val & WDOG_CONTROL_REG_WDT_EN_MASK)
148 writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
149 WDOG_COUNTER_RESTART_REG_OFFSET);
151 writel(WDOG_CONTROL_REG_WDT_EN_MASK,
152 dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
154 /* wait for reset to assert... */
160 static void dw_wdt_ping(unsigned long data)
162 if (time_before(jiffies, dw_wdt.next_heartbeat) ||
163 (!nowayout && !dw_wdt.in_use)) {
165 mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
167 pr_crit("keepalive missed, machine will reset\n");
170 static int dw_wdt_open(struct inode *inode, struct file *filp)
172 if (test_and_set_bit(0, &dw_wdt.in_use))
175 /* Make sure we don't get unloaded. */
176 __module_get(THIS_MODULE);
178 if (!dw_wdt_is_enabled()) {
180 * The watchdog is not currently enabled. Set the timeout to
181 * something reasonable and then start it.
183 dw_wdt_set_top(DW_WDT_DEFAULT_SECONDS);
184 writel(WDOG_CONTROL_REG_WDT_EN_MASK,
185 dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
188 dw_wdt_set_next_heartbeat();
190 return nonseekable_open(inode, filp);
193 static ssize_t dw_wdt_write(struct file *filp, const char __user *buf,
194 size_t len, loff_t *offset)
202 dw_wdt.expect_close = 0;
204 for (i = 0; i < len; ++i) {
207 if (get_user(c, buf + i))
211 dw_wdt.expect_close = 1;
217 dw_wdt_set_next_heartbeat();
219 mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
224 static u32 dw_wdt_time_left(void)
226 return readl(dw_wdt.regs + WDOG_CURRENT_COUNT_REG_OFFSET) /
227 clk_get_rate(dw_wdt.clk);
230 static const struct watchdog_info dw_wdt_ident = {
231 .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
233 .identity = "Synopsys DesignWare Watchdog",
236 static long dw_wdt_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
242 case WDIOC_GETSUPPORT:
243 return copy_to_user((void __user *)arg, &dw_wdt_ident,
244 sizeof(dw_wdt_ident)) ? -EFAULT : 0;
246 case WDIOC_GETSTATUS:
247 case WDIOC_GETBOOTSTATUS:
248 return put_user(0, (int __user *)arg);
250 case WDIOC_KEEPALIVE:
251 dw_wdt_set_next_heartbeat();
254 case WDIOC_SETTIMEOUT:
255 if (get_user(val, (int __user *)arg))
257 timeout = dw_wdt_set_top(val);
258 return put_user(timeout , (int __user *)arg);
260 case WDIOC_GETTIMEOUT:
261 return put_user(dw_wdt_get_top(), (int __user *)arg);
263 case WDIOC_GETTIMELEFT:
264 /* Get the time left until expiry. */
265 if (get_user(val, (int __user *)arg))
267 return put_user(dw_wdt_time_left(), (int __user *)arg);
274 static int dw_wdt_release(struct inode *inode, struct file *filp)
276 clear_bit(0, &dw_wdt.in_use);
278 if (!dw_wdt.expect_close) {
279 del_timer(&dw_wdt.timer);
282 pr_crit("unexpected close, system will reboot soon\n");
284 pr_crit("watchdog cannot be disabled, system will reboot soon\n");
287 dw_wdt.expect_close = 0;
292 #ifdef CONFIG_PM_SLEEP
293 static int dw_wdt_suspend(struct device *dev)
295 clk_disable_unprepare(dw_wdt.clk);
300 static int dw_wdt_resume(struct device *dev)
302 int err = clk_prepare_enable(dw_wdt.clk);
311 #endif /* CONFIG_PM_SLEEP */
313 static SIMPLE_DEV_PM_OPS(dw_wdt_pm_ops, dw_wdt_suspend, dw_wdt_resume);
315 static const struct file_operations wdt_fops = {
316 .owner = THIS_MODULE,
319 .write = dw_wdt_write,
320 .unlocked_ioctl = dw_wdt_ioctl,
321 .release = dw_wdt_release
324 static struct miscdevice dw_wdt_miscdev = {
327 .minor = WATCHDOG_MINOR,
330 static int dw_wdt_drv_probe(struct platform_device *pdev)
333 struct resource *mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
335 dw_wdt.regs = devm_ioremap_resource(&pdev->dev, mem);
336 if (IS_ERR(dw_wdt.regs))
337 return PTR_ERR(dw_wdt.regs);
339 dw_wdt.clk = devm_clk_get(&pdev->dev, NULL);
340 if (IS_ERR(dw_wdt.clk))
341 return PTR_ERR(dw_wdt.clk);
343 ret = clk_prepare_enable(dw_wdt.clk);
347 ret = misc_register(&dw_wdt_miscdev);
349 goto out_disable_clk;
351 dw_wdt.restart_handler.notifier_call = dw_wdt_restart_handle;
352 dw_wdt.restart_handler.priority = 128;
353 ret = register_restart_handler(&dw_wdt.restart_handler);
355 pr_warn("cannot register restart handler\n");
357 dw_wdt_set_next_heartbeat();
358 setup_timer(&dw_wdt.timer, dw_wdt_ping, 0);
359 mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
364 clk_disable_unprepare(dw_wdt.clk);
369 static int dw_wdt_drv_remove(struct platform_device *pdev)
371 unregister_restart_handler(&dw_wdt.restart_handler);
373 misc_deregister(&dw_wdt_miscdev);
375 clk_disable_unprepare(dw_wdt.clk);
381 static const struct of_device_id dw_wdt_of_match[] = {
382 { .compatible = "snps,dw-wdt", },
385 MODULE_DEVICE_TABLE(of, dw_wdt_of_match);
388 static struct platform_driver dw_wdt_driver = {
389 .probe = dw_wdt_drv_probe,
390 .remove = dw_wdt_drv_remove,
393 .of_match_table = of_match_ptr(dw_wdt_of_match),
394 .pm = &dw_wdt_pm_ops,
398 module_platform_driver(dw_wdt_driver);
400 MODULE_AUTHOR("Jamie Iles");
401 MODULE_DESCRIPTION("Synopsys DesignWare Watchdog Driver");
402 MODULE_LICENSE("GPL");