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/spinlock.h>
39#include <linux/timer.h>
40#include <linux/uaccess.h>
41#include <linux/watchdog.h>
42
43#define WDOG_CONTROL_REG_OFFSET		    0x00
44#define WDOG_CONTROL_REG_WDT_EN_MASK	    0x01
45#define WDOG_TIMEOUT_RANGE_REG_OFFSET	    0x04
46#define WDOG_TIMEOUT_RANGE_TOPINIT_SHIFT    4
47#define WDOG_CURRENT_COUNT_REG_OFFSET	    0x08
48#define WDOG_COUNTER_RESTART_REG_OFFSET     0x0c
49#define WDOG_COUNTER_RESTART_KICK_VALUE	    0x76
50
51/* The maximum TOP (timeout period) value that can be set in the watchdog. */
52#define DW_WDT_MAX_TOP		15
53
54#define DW_WDT_DEFAULT_SECONDS	30
55
56static bool nowayout = WATCHDOG_NOWAYOUT;
57module_param(nowayout, bool, 0);
58MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
59		 "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
60
61#define WDT_TIMEOUT		(HZ / 2)
62
63static struct {
64	spinlock_t		lock;
65	void __iomem		*regs;
66	struct clk		*clk;
67	unsigned long		in_use;
68	unsigned long		next_heartbeat;
69	struct timer_list	timer;
70	int			expect_close;
71	struct notifier_block	restart_handler;
72} dw_wdt;
73
74static inline int dw_wdt_is_enabled(void)
75{
76	return readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET) &
77		WDOG_CONTROL_REG_WDT_EN_MASK;
78}
79
80static inline int dw_wdt_top_in_seconds(unsigned top)
81{
82	/*
83	 * There are 16 possible timeout values in 0..15 where the number of
84	 * cycles is 2 ^ (16 + i) and the watchdog counts down.
85	 */
86	return (1 << (16 + top)) / clk_get_rate(dw_wdt.clk);
87}
88
89static int dw_wdt_get_top(void)
90{
91	int top = readl(dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET) & 0xF;
92
93	return dw_wdt_top_in_seconds(top);
94}
95
96static inline void dw_wdt_set_next_heartbeat(void)
97{
98	dw_wdt.next_heartbeat = jiffies + dw_wdt_get_top() * HZ;
99}
100
101static void dw_wdt_keepalive(void)
102{
103	writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
104	       WDOG_COUNTER_RESTART_REG_OFFSET);
105}
106
107static int dw_wdt_set_top(unsigned top_s)
108{
109	int i, top_val = DW_WDT_MAX_TOP;
110
111	/*
112	 * Iterate over the timeout values until we find the closest match. We
113	 * always look for >=.
114	 */
115	for (i = 0; i <= DW_WDT_MAX_TOP; ++i)
116		if (dw_wdt_top_in_seconds(i) >= top_s) {
117			top_val = i;
118			break;
119		}
120
121	/*
122	 * Set the new value in the watchdog.  Some versions of dw_wdt
123	 * have have TOPINIT in the TIMEOUT_RANGE register (as per
124	 * CP_WDT_DUAL_TOP in WDT_COMP_PARAMS_1).  On those we
125	 * effectively get a pat of the watchdog right here.
126	 */
127	writel(top_val | top_val << WDOG_TIMEOUT_RANGE_TOPINIT_SHIFT,
128		dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);
129
130	/*
131	 * Add an explicit pat to handle versions of the watchdog that
132	 * don't have TOPINIT.  This won't hurt on versions that have
133	 * it.
134	 */
135	dw_wdt_keepalive();
136
137	dw_wdt_set_next_heartbeat();
138
139	return dw_wdt_top_in_seconds(top_val);
140}
141
142static int dw_wdt_restart_handle(struct notifier_block *this,
143				unsigned long mode, void *cmd)
144{
145	u32 val;
146
147	writel(0, dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);
148	val = readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
149	if (val & WDOG_CONTROL_REG_WDT_EN_MASK)
150		writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
151			WDOG_COUNTER_RESTART_REG_OFFSET);
152	else
153		writel(WDOG_CONTROL_REG_WDT_EN_MASK,
154		       dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
155
156	/* wait for reset to assert... */
157	mdelay(500);
158
159	return NOTIFY_DONE;
160}
161
162static void dw_wdt_ping(unsigned long data)
163{
164	if (time_before(jiffies, dw_wdt.next_heartbeat) ||
165	    (!nowayout && !dw_wdt.in_use)) {
166		dw_wdt_keepalive();
167		mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
168	} else
169		pr_crit("keepalive missed, machine will reset\n");
170}
171
172static int dw_wdt_open(struct inode *inode, struct file *filp)
173{
174	if (test_and_set_bit(0, &dw_wdt.in_use))
175		return -EBUSY;
176
177	/* Make sure we don't get unloaded. */
178	__module_get(THIS_MODULE);
179
180	spin_lock(&dw_wdt.lock);
181	if (!dw_wdt_is_enabled()) {
182		/*
183		 * The watchdog is not currently enabled. Set the timeout to
184		 * something reasonable and then start it.
185		 */
186		dw_wdt_set_top(DW_WDT_DEFAULT_SECONDS);
187		writel(WDOG_CONTROL_REG_WDT_EN_MASK,
188		       dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
189	}
190
191	dw_wdt_set_next_heartbeat();
192
193	spin_unlock(&dw_wdt.lock);
194
195	return nonseekable_open(inode, filp);
196}
197
198static ssize_t dw_wdt_write(struct file *filp, const char __user *buf,
199			    size_t len, loff_t *offset)
200{
201	if (!len)
202		return 0;
203
204	if (!nowayout) {
205		size_t i;
206
207		dw_wdt.expect_close = 0;
208
209		for (i = 0; i < len; ++i) {
210			char c;
211
212			if (get_user(c, buf + i))
213				return -EFAULT;
214
215			if (c == 'V') {
216				dw_wdt.expect_close = 1;
217				break;
218			}
219		}
220	}
221
222	dw_wdt_set_next_heartbeat();
223	mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
224
225	return len;
226}
227
228static u32 dw_wdt_time_left(void)
229{
230	return readl(dw_wdt.regs + WDOG_CURRENT_COUNT_REG_OFFSET) /
231		clk_get_rate(dw_wdt.clk);
232}
233
234static const struct watchdog_info dw_wdt_ident = {
235	.options	= WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
236			  WDIOF_MAGICCLOSE,
237	.identity	= "Synopsys DesignWare Watchdog",
238};
239
240static long dw_wdt_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
241{
242	unsigned long val;
243	int timeout;
244
245	switch (cmd) {
246	case WDIOC_GETSUPPORT:
247		return copy_to_user((void __user *)arg, &dw_wdt_ident,
248				    sizeof(dw_wdt_ident)) ? -EFAULT : 0;
249
250	case WDIOC_GETSTATUS:
251	case WDIOC_GETBOOTSTATUS:
252		return put_user(0, (int __user *)arg);
253
254	case WDIOC_KEEPALIVE:
255		dw_wdt_set_next_heartbeat();
256		return 0;
257
258	case WDIOC_SETTIMEOUT:
259		if (get_user(val, (int __user *)arg))
260			return -EFAULT;
261		timeout = dw_wdt_set_top(val);
262		return put_user(timeout , (int __user *)arg);
263
264	case WDIOC_GETTIMEOUT:
265		return put_user(dw_wdt_get_top(), (int __user *)arg);
266
267	case WDIOC_GETTIMELEFT:
268		/* Get the time left until expiry. */
269		if (get_user(val, (int __user *)arg))
270			return -EFAULT;
271		return put_user(dw_wdt_time_left(), (int __user *)arg);
272
273	default:
274		return -ENOTTY;
275	}
276}
277
278static int dw_wdt_release(struct inode *inode, struct file *filp)
279{
280	clear_bit(0, &dw_wdt.in_use);
281
282	if (!dw_wdt.expect_close) {
283		del_timer(&dw_wdt.timer);
284
285		if (!nowayout)
286			pr_crit("unexpected close, system will reboot soon\n");
287		else
288			pr_crit("watchdog cannot be disabled, system will reboot soon\n");
289	}
290
291	dw_wdt.expect_close = 0;
292
293	return 0;
294}
295
296#ifdef CONFIG_PM_SLEEP
297static int dw_wdt_suspend(struct device *dev)
298{
299	clk_disable_unprepare(dw_wdt.clk);
300
301	return 0;
302}
303
304static int dw_wdt_resume(struct device *dev)
305{
306	int err = clk_prepare_enable(dw_wdt.clk);
307
308	if (err)
309		return err;
310
311	dw_wdt_keepalive();
312
313	return 0;
314}
315#endif /* CONFIG_PM_SLEEP */
316
317static SIMPLE_DEV_PM_OPS(dw_wdt_pm_ops, dw_wdt_suspend, dw_wdt_resume);
318
319static const struct file_operations wdt_fops = {
320	.owner		= THIS_MODULE,
321	.llseek		= no_llseek,
322	.open		= dw_wdt_open,
323	.write		= dw_wdt_write,
324	.unlocked_ioctl	= dw_wdt_ioctl,
325	.release	= dw_wdt_release
326};
327
328static struct miscdevice dw_wdt_miscdev = {
329	.fops		= &wdt_fops,
330	.name		= "watchdog",
331	.minor		= WATCHDOG_MINOR,
332};
333
334static int dw_wdt_drv_probe(struct platform_device *pdev)
335{
336	int ret;
337	struct resource *mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
338
339	dw_wdt.regs = devm_ioremap_resource(&pdev->dev, mem);
340	if (IS_ERR(dw_wdt.regs))
341		return PTR_ERR(dw_wdt.regs);
342
343	dw_wdt.clk = devm_clk_get(&pdev->dev, NULL);
344	if (IS_ERR(dw_wdt.clk))
345		return PTR_ERR(dw_wdt.clk);
346
347	ret = clk_prepare_enable(dw_wdt.clk);
348	if (ret)
349		return ret;
350
351	spin_lock_init(&dw_wdt.lock);
352
353	ret = misc_register(&dw_wdt_miscdev);
354	if (ret)
355		goto out_disable_clk;
356
357	dw_wdt.restart_handler.notifier_call = dw_wdt_restart_handle;
358	dw_wdt.restart_handler.priority = 128;
359	ret = register_restart_handler(&dw_wdt.restart_handler);
360	if (ret)
361		pr_warn("cannot register restart handler\n");
362
363	dw_wdt_set_next_heartbeat();
364	setup_timer(&dw_wdt.timer, dw_wdt_ping, 0);
365	mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
366
367	return 0;
368
369out_disable_clk:
370	clk_disable_unprepare(dw_wdt.clk);
371
372	return ret;
373}
374
375static int dw_wdt_drv_remove(struct platform_device *pdev)
376{
377	unregister_restart_handler(&dw_wdt.restart_handler);
378
379	misc_deregister(&dw_wdt_miscdev);
380
381	clk_disable_unprepare(dw_wdt.clk);
382
383	return 0;
384}
385
386#ifdef CONFIG_OF
387static const struct of_device_id dw_wdt_of_match[] = {
388	{ .compatible = "snps,dw-wdt", },
389	{ /* sentinel */ }
390};
391MODULE_DEVICE_TABLE(of, dw_wdt_of_match);
392#endif
393
394static struct platform_driver dw_wdt_driver = {
395	.probe		= dw_wdt_drv_probe,
396	.remove		= dw_wdt_drv_remove,
397	.driver		= {
398		.name	= "dw_wdt",
399		.of_match_table = of_match_ptr(dw_wdt_of_match),
400		.pm	= &dw_wdt_pm_ops,
401	},
402};
403
404module_platform_driver(dw_wdt_driver);
405
406MODULE_AUTHOR("Jamie Iles");
407MODULE_DESCRIPTION("Synopsys DesignWare Watchdog Driver");
408MODULE_LICENSE("GPL");
409