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

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