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[linux-2.6.git] / drivers / watchdog / dw_wdt.c
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 ARM 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 #define pr_fmt(fmt) "dw_wdt: " fmt
20
21 #include <linux/bitops.h>
22 #include <linux/clk.h>
23 #include <linux/device.h>
24 #include <linux/err.h>
25 #include <linux/fs.h>
26 #include <linux/io.h>
27 #include <linux/kernel.h>
28 #include <linux/miscdevice.h>
29 #include <linux/module.h>
30 #include <linux/moduleparam.h>
31 #include <linux/pm.h>
32 #include <linux/platform_device.h>
33 #include <linux/spinlock.h>
34 #include <linux/timer.h>
35 #include <linux/uaccess.h>
36 #include <linux/watchdog.h>
37
38 #define WDOG_CONTROL_REG_OFFSET             0x00
39 #define WDOG_CONTROL_REG_WDT_EN_MASK        0x01
40 #define WDOG_TIMEOUT_RANGE_REG_OFFSET       0x04
41 #define WDOG_CURRENT_COUNT_REG_OFFSET       0x08
42 #define WDOG_COUNTER_RESTART_REG_OFFSET     0x0c
43 #define WDOG_COUNTER_RESTART_KICK_VALUE     0x76
44
45 /* The maximum TOP (timeout period) value that can be set in the watchdog. */
46 #define DW_WDT_MAX_TOP          15
47
48 static int nowayout = WATCHDOG_NOWAYOUT;
49 module_param(nowayout, int, 0);
50 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
51                  "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
52
53 #define WDT_TIMEOUT             (HZ / 2)
54
55 static struct {
56         spinlock_t              lock;
57         void __iomem            *regs;
58         struct clk              *clk;
59         unsigned long           in_use;
60         unsigned long           next_heartbeat;
61         struct timer_list       timer;
62         int                     expect_close;
63 } dw_wdt;
64
65 static inline int dw_wdt_is_enabled(void)
66 {
67         return readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET) &
68                 WDOG_CONTROL_REG_WDT_EN_MASK;
69 }
70
71 static inline int dw_wdt_top_in_seconds(unsigned top)
72 {
73         /*
74          * There are 16 possible timeout values in 0..15 where the number of
75          * cycles is 2 ^ (16 + i) and the watchdog counts down.
76          */
77         return (1 << (16 + top)) / clk_get_rate(dw_wdt.clk);
78 }
79
80 static int dw_wdt_get_top(void)
81 {
82         int top = readl(dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET) & 0xF;
83
84         return dw_wdt_top_in_seconds(top);
85 }
86
87 static inline void dw_wdt_set_next_heartbeat(void)
88 {
89         dw_wdt.next_heartbeat = jiffies + dw_wdt_get_top() * HZ;
90 }
91
92 static int dw_wdt_set_top(unsigned top_s)
93 {
94         int i, top_val = DW_WDT_MAX_TOP;
95
96         /*
97          * Iterate over the timeout values until we find the closest match. We
98          * always look for >=.
99          */
100         for (i = 0; i <= DW_WDT_MAX_TOP; ++i)
101                 if (dw_wdt_top_in_seconds(i) >= top_s) {
102                         top_val = i;
103                         break;
104                 }
105
106         /* Set the new value in the watchdog. */
107         writel(top_val, dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);
108
109         dw_wdt_set_next_heartbeat();
110
111         return dw_wdt_top_in_seconds(top_val);
112 }
113
114 static void dw_wdt_keepalive(void)
115 {
116         writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
117                WDOG_COUNTER_RESTART_REG_OFFSET);
118 }
119
120 static void dw_wdt_ping(unsigned long data)
121 {
122         if (time_before(jiffies, dw_wdt.next_heartbeat) ||
123             (!nowayout && !dw_wdt.in_use)) {
124                 dw_wdt_keepalive();
125                 mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
126         } else
127                 pr_crit("keepalive missed, machine will reset\n");
128 }
129
130 static int dw_wdt_open(struct inode *inode, struct file *filp)
131 {
132         if (test_and_set_bit(0, &dw_wdt.in_use))
133                 return -EBUSY;
134
135         /* Make sure we don't get unloaded. */
136         __module_get(THIS_MODULE);
137
138         spin_lock(&dw_wdt.lock);
139         if (!dw_wdt_is_enabled()) {
140                 /*
141                  * The watchdog is not currently enabled. Set the timeout to
142                  * the maximum and then start it.
143                  */
144                 dw_wdt_set_top(DW_WDT_MAX_TOP);
145                 writel(WDOG_CONTROL_REG_WDT_EN_MASK,
146                        dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
147         }
148
149         dw_wdt_set_next_heartbeat();
150
151         spin_unlock(&dw_wdt.lock);
152
153         return nonseekable_open(inode, filp);
154 }
155
156 ssize_t dw_wdt_write(struct file *filp, const char __user *buf, size_t len,
157                      loff_t *offset)
158 {
159         if (!len)
160                 return 0;
161
162         if (!nowayout) {
163                 size_t i;
164
165                 dw_wdt.expect_close = 0;
166
167                 for (i = 0; i < len; ++i) {
168                         char c;
169
170                         if (get_user(c, buf + i))
171                                 return -EFAULT;
172
173                         if (c == 'V') {
174                                 dw_wdt.expect_close = 1;
175                                 break;
176                         }
177                 }
178         }
179
180         dw_wdt_set_next_heartbeat();
181         mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
182
183         return len;
184 }
185
186 static u32 dw_wdt_time_left(void)
187 {
188         return readl(dw_wdt.regs + WDOG_CURRENT_COUNT_REG_OFFSET) /
189                 clk_get_rate(dw_wdt.clk);
190 }
191
192 static const struct watchdog_info dw_wdt_ident = {
193         .options        = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
194                           WDIOF_MAGICCLOSE,
195         .identity       = "Synopsys DesignWare Watchdog",
196 };
197
198 static long dw_wdt_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
199 {
200         unsigned long val;
201         int timeout;
202
203         switch (cmd) {
204         case WDIOC_GETSUPPORT:
205                 return copy_to_user((struct watchdog_info *)arg, &dw_wdt_ident,
206                                     sizeof(dw_wdt_ident)) ? -EFAULT : 0;
207
208         case WDIOC_GETSTATUS:
209         case WDIOC_GETBOOTSTATUS:
210                 return put_user(0, (int *)arg);
211
212         case WDIOC_KEEPALIVE:
213                 dw_wdt_set_next_heartbeat();
214                 return 0;
215
216         case WDIOC_SETTIMEOUT:
217                 if (get_user(val, (int __user *)arg))
218                         return -EFAULT;
219                 timeout = dw_wdt_set_top(val);
220                 return put_user(timeout , (int __user *)arg);
221
222         case WDIOC_GETTIMEOUT:
223                 return put_user(dw_wdt_get_top(), (int __user *)arg);
224
225         case WDIOC_GETTIMELEFT:
226                 /* Get the time left until expiry. */
227                 if (get_user(val, (int __user *)arg))
228                         return -EFAULT;
229                 return put_user(dw_wdt_time_left(), (int __user *)arg);
230
231         default:
232                 return -ENOTTY;
233         }
234 }
235
236 static int dw_wdt_release(struct inode *inode, struct file *filp)
237 {
238         clear_bit(0, &dw_wdt.in_use);
239
240         if (!dw_wdt.expect_close) {
241                 del_timer(&dw_wdt.timer);
242
243                 if (!nowayout)
244                         pr_crit("unexpected close, system will reboot soon\n");
245                 else
246                         pr_crit("watchdog cannot be disabled, system will reboot soon\n");
247         }
248
249         dw_wdt.expect_close = 0;
250
251         return 0;
252 }
253
254 #ifdef CONFIG_PM
255 static int dw_wdt_suspend(struct device *dev)
256 {
257         clk_disable(dw_wdt.clk);
258
259         return 0;
260 }
261
262 static int dw_wdt_resume(struct device *dev)
263 {
264         int err = clk_enable(dw_wdt.clk);
265
266         if (err)
267                 return err;
268
269         dw_wdt_keepalive();
270
271         return 0;
272 }
273
274 static const struct dev_pm_ops dw_wdt_pm_ops = {
275         .suspend        = dw_wdt_suspend,
276         .resume         = dw_wdt_resume,
277 };
278 #endif /* CONFIG_PM */
279
280 static const struct file_operations wdt_fops = {
281         .owner          = THIS_MODULE,
282         .llseek         = no_llseek,
283         .open           = dw_wdt_open,
284         .write          = dw_wdt_write,
285         .unlocked_ioctl = dw_wdt_ioctl,
286         .release        = dw_wdt_release
287 };
288
289 static struct miscdevice dw_wdt_miscdev = {
290         .fops           = &wdt_fops,
291         .name           = "watchdog",
292         .minor          = WATCHDOG_MINOR,
293 };
294
295 static int __devinit dw_wdt_drv_probe(struct platform_device *pdev)
296 {
297         int ret;
298         struct resource *mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
299
300         if (!mem)
301                 return -EINVAL;
302
303         if (!devm_request_mem_region(&pdev->dev, mem->start, resource_size(mem),
304                                      "dw_wdt"))
305                 return -ENOMEM;
306
307         dw_wdt.regs = devm_ioremap(&pdev->dev, mem->start, resource_size(mem));
308         if (!dw_wdt.regs)
309                 return -ENOMEM;
310
311         dw_wdt.clk = clk_get(&pdev->dev, NULL);
312         if (IS_ERR(dw_wdt.clk))
313                 return PTR_ERR(dw_wdt.clk);
314
315         ret = clk_enable(dw_wdt.clk);
316         if (ret)
317                 goto out_put_clk;
318
319         spin_lock_init(&dw_wdt.lock);
320
321         ret = misc_register(&dw_wdt_miscdev);
322         if (ret)
323                 goto out_disable_clk;
324
325         dw_wdt_set_next_heartbeat();
326         setup_timer(&dw_wdt.timer, dw_wdt_ping, 0);
327         mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
328
329         return 0;
330
331 out_disable_clk:
332         clk_disable(dw_wdt.clk);
333 out_put_clk:
334         clk_put(dw_wdt.clk);
335
336         return ret;
337 }
338
339 static int __devexit dw_wdt_drv_remove(struct platform_device *pdev)
340 {
341         misc_deregister(&dw_wdt_miscdev);
342
343         clk_disable(dw_wdt.clk);
344         clk_put(dw_wdt.clk);
345
346         return 0;
347 }
348
349 static struct platform_driver dw_wdt_driver = {
350         .probe          = dw_wdt_drv_probe,
351         .remove         = __devexit_p(dw_wdt_drv_remove),
352         .driver         = {
353                 .name   = "dw_wdt",
354                 .owner  = THIS_MODULE,
355 #ifdef CONFIG_PM
356                 .pm     = &dw_wdt_pm_ops,
357 #endif /* CONFIG_PM */
358         },
359 };
360
361 static int __init dw_wdt_watchdog_init(void)
362 {
363         return platform_driver_register(&dw_wdt_driver);
364 }
365 module_init(dw_wdt_watchdog_init);
366
367 static void __exit dw_wdt_watchdog_exit(void)
368 {
369         platform_driver_unregister(&dw_wdt_driver);
370 }
371 module_exit(dw_wdt_watchdog_exit);
372
373 MODULE_AUTHOR("Jamie Iles");
374 MODULE_DESCRIPTION("Synopsys DesignWare Watchdog Driver");
375 MODULE_LICENSE("GPL");
376 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);