1/*
2 * Copyright 2010-2011 Picochip Ltd., Jamie Iles
3 * http://www.picochip.com
4 *
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.
9 *
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.
13 *
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.
18 */
19
20#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
21
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>
27#include <linux/fs.h>
28#include <linux/io.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>
34#include <linux/of.h>
35#include <linux/pm.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>
41
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
49
50/* The maximum TOP (timeout period) value that can be set in the watchdog. */
51#define DW_WDT_MAX_TOP		15
52
53#define DW_WDT_DEFAULT_SECONDS	30
54
55static bool nowayout = WATCHDOG_NOWAYOUT;
56module_param(nowayout, bool, 0);
57MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
58		 "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
59
60#define WDT_TIMEOUT		(HZ / 2)
61
62static struct {
63	void __iomem		*regs;
64	struct clk		*clk;
65	unsigned long		in_use;
66	unsigned long		next_heartbeat;
67	struct timer_list	timer;
68	int			expect_close;
69	struct notifier_block	restart_handler;
70} dw_wdt;
71
72static inline int dw_wdt_is_enabled(void)
73{
74	return readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET) &
75		WDOG_CONTROL_REG_WDT_EN_MASK;
76}
77
78static inline int dw_wdt_top_in_seconds(unsigned top)
79{
80	/*
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.
83	 */
84	return (1 << (16 + top)) / clk_get_rate(dw_wdt.clk);
85}
86
87static int dw_wdt_get_top(void)
88{
89	int top = readl(dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET) & 0xF;
90
91	return dw_wdt_top_in_seconds(top);
92}
93
94static inline void dw_wdt_set_next_heartbeat(void)
95{
96	dw_wdt.next_heartbeat = jiffies + dw_wdt_get_top() * HZ;
97}
98
99static void dw_wdt_keepalive(void)
100{
101	writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
102	       WDOG_COUNTER_RESTART_REG_OFFSET);
103}
104
105static int dw_wdt_set_top(unsigned top_s)
106{
107	int i, top_val = DW_WDT_MAX_TOP;
108
109	/*
110	 * Iterate over the timeout values until we find the closest match. We
111	 * always look for >=.
112	 */
113	for (i = 0; i <= DW_WDT_MAX_TOP; ++i)
114		if (dw_wdt_top_in_seconds(i) >= top_s) {
115			top_val = i;
116			break;
117		}
118
119	/*
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.
124	 */
125	writel(top_val | top_val << WDOG_TIMEOUT_RANGE_TOPINIT_SHIFT,
126		dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);
127
128	/*
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
131	 * it.
132	 */
133	dw_wdt_keepalive();
134
135	dw_wdt_set_next_heartbeat();
136
137	return dw_wdt_top_in_seconds(top_val);
138}
139
140static int dw_wdt_restart_handle(struct notifier_block *this,
141				unsigned long mode, void *cmd)
142{
143	u32 val;
144
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);
150	else
151		writel(WDOG_CONTROL_REG_WDT_EN_MASK,
152		       dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
153
154	/* wait for reset to assert... */
155	mdelay(500);
156
157	return NOTIFY_DONE;
158}
159
160static void dw_wdt_ping(unsigned long data)
161{
162	if (time_before(jiffies, dw_wdt.next_heartbeat) ||
163	    (!nowayout && !dw_wdt.in_use)) {
164		dw_wdt_keepalive();
165		mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
166	} else
167		pr_crit("keepalive missed, machine will reset\n");
168}
169
170static int dw_wdt_open(struct inode *inode, struct file *filp)
171{
172	if (test_and_set_bit(0, &dw_wdt.in_use))
173		return -EBUSY;
174
175	/* Make sure we don't get unloaded. */
176	__module_get(THIS_MODULE);
177
178	if (!dw_wdt_is_enabled()) {
179		/*
180		 * The watchdog is not currently enabled. Set the timeout to
181		 * something reasonable and then start it.
182		 */
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);
186	}
187
188	dw_wdt_set_next_heartbeat();
189
190	return nonseekable_open(inode, filp);
191}
192
193static ssize_t dw_wdt_write(struct file *filp, const char __user *buf,
194			    size_t len, loff_t *offset)
195{
196	if (!len)
197		return 0;
198
199	if (!nowayout) {
200		size_t i;
201
202		dw_wdt.expect_close = 0;
203
204		for (i = 0; i < len; ++i) {
205			char c;
206
207			if (get_user(c, buf + i))
208				return -EFAULT;
209
210			if (c == 'V') {
211				dw_wdt.expect_close = 1;
212				break;
213			}
214		}
215	}
216
217	dw_wdt_set_next_heartbeat();
218	dw_wdt_keepalive();
219	mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
220
221	return len;
222}
223
224static u32 dw_wdt_time_left(void)
225{
226	return readl(dw_wdt.regs + WDOG_CURRENT_COUNT_REG_OFFSET) /
227		clk_get_rate(dw_wdt.clk);
228}
229
230static const struct watchdog_info dw_wdt_ident = {
231	.options	= WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
232			  WDIOF_MAGICCLOSE,
233	.identity	= "Synopsys DesignWare Watchdog",
234};
235
236static long dw_wdt_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
237{
238	unsigned long val;
239	int timeout;
240
241	switch (cmd) {
242	case WDIOC_GETSUPPORT:
243		return copy_to_user((void __user *)arg, &dw_wdt_ident,
244				    sizeof(dw_wdt_ident)) ? -EFAULT : 0;
245
246	case WDIOC_GETSTATUS:
247	case WDIOC_GETBOOTSTATUS:
248		return put_user(0, (int __user *)arg);
249
250	case WDIOC_KEEPALIVE:
251		dw_wdt_set_next_heartbeat();
252		return 0;
253
254	case WDIOC_SETTIMEOUT:
255		if (get_user(val, (int __user *)arg))
256			return -EFAULT;
257		timeout = dw_wdt_set_top(val);
258		return put_user(timeout , (int __user *)arg);
259
260	case WDIOC_GETTIMEOUT:
261		return put_user(dw_wdt_get_top(), (int __user *)arg);
262
263	case WDIOC_GETTIMELEFT:
264		/* Get the time left until expiry. */
265		if (get_user(val, (int __user *)arg))
266			return -EFAULT;
267		return put_user(dw_wdt_time_left(), (int __user *)arg);
268
269	default:
270		return -ENOTTY;
271	}
272}
273
274static int dw_wdt_release(struct inode *inode, struct file *filp)
275{
276	clear_bit(0, &dw_wdt.in_use);
277
278	if (!dw_wdt.expect_close) {
279		del_timer(&dw_wdt.timer);
280
281		if (!nowayout)
282			pr_crit("unexpected close, system will reboot soon\n");
283		else
284			pr_crit("watchdog cannot be disabled, system will reboot soon\n");
285	}
286
287	dw_wdt.expect_close = 0;
288
289	return 0;
290}
291
292#ifdef CONFIG_PM_SLEEP
293static int dw_wdt_suspend(struct device *dev)
294{
295	clk_disable_unprepare(dw_wdt.clk);
296
297	return 0;
298}
299
300static int dw_wdt_resume(struct device *dev)
301{
302	int err = clk_prepare_enable(dw_wdt.clk);
303
304	if (err)
305		return err;
306
307	dw_wdt_keepalive();
308
309	return 0;
310}
311#endif /* CONFIG_PM_SLEEP */
312
313static SIMPLE_DEV_PM_OPS(dw_wdt_pm_ops, dw_wdt_suspend, dw_wdt_resume);
314
315static const struct file_operations wdt_fops = {
316	.owner		= THIS_MODULE,
317	.llseek		= no_llseek,
318	.open		= dw_wdt_open,
319	.write		= dw_wdt_write,
320	.unlocked_ioctl	= dw_wdt_ioctl,
321	.release	= dw_wdt_release
322};
323
324static struct miscdevice dw_wdt_miscdev = {
325	.fops		= &wdt_fops,
326	.name		= "watchdog",
327	.minor		= WATCHDOG_MINOR,
328};
329
330static int dw_wdt_drv_probe(struct platform_device *pdev)
331{
332	int ret;
333	struct resource *mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
334
335	dw_wdt.regs = devm_ioremap_resource(&pdev->dev, mem);
336	if (IS_ERR(dw_wdt.regs))
337		return PTR_ERR(dw_wdt.regs);
338
339	dw_wdt.clk = devm_clk_get(&pdev->dev, NULL);
340	if (IS_ERR(dw_wdt.clk))
341		return PTR_ERR(dw_wdt.clk);
342
343	ret = clk_prepare_enable(dw_wdt.clk);
344	if (ret)
345		return ret;
346
347	ret = misc_register(&dw_wdt_miscdev);
348	if (ret)
349		goto out_disable_clk;
350
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);
354	if (ret)
355		pr_warn("cannot register restart handler\n");
356
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);
360
361	return 0;
362
363out_disable_clk:
364	clk_disable_unprepare(dw_wdt.clk);
365
366	return ret;
367}
368
369static int dw_wdt_drv_remove(struct platform_device *pdev)
370{
371	unregister_restart_handler(&dw_wdt.restart_handler);
372
373	misc_deregister(&dw_wdt_miscdev);
374
375	clk_disable_unprepare(dw_wdt.clk);
376
377	return 0;
378}
379
380#ifdef CONFIG_OF
381static const struct of_device_id dw_wdt_of_match[] = {
382	{ .compatible = "snps,dw-wdt", },
383	{ /* sentinel */ }
384};
385MODULE_DEVICE_TABLE(of, dw_wdt_of_match);
386#endif
387
388static struct platform_driver dw_wdt_driver = {
389	.probe		= dw_wdt_drv_probe,
390	.remove		= dw_wdt_drv_remove,
391	.driver		= {
392		.name	= "dw_wdt",
393		.of_match_table = of_match_ptr(dw_wdt_of_match),
394		.pm	= &dw_wdt_pm_ops,
395	},
396};
397
398module_platform_driver(dw_wdt_driver);
399
400MODULE_AUTHOR("Jamie Iles");
401MODULE_DESCRIPTION("Synopsys DesignWare Watchdog Driver");
402MODULE_LICENSE("GPL");
403