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