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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 #define DW_WDT_DEFAULT_SECONDS  30
 55 
 56 static bool nowayout = WATCHDOG_NOWAYOUT;
 57 module_param(nowayout, bool, 0);
 58 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
 59                  "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
 60 
 61 #define WDT_TIMEOUT             (HZ / 2)
 62 
 63 static 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 
 74 static 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 
 80 static 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 
 89 static 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 
 96 static inline void dw_wdt_set_next_heartbeat(void)
 97 {
 98         dw_wdt.next_heartbeat = jiffies + dw_wdt_get_top() * HZ;
 99 }
100 
101 static void dw_wdt_keepalive(void)
102 {
103         writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
104                WDOG_COUNTER_RESTART_REG_OFFSET);
105 }
106 
107 static 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 
142 static 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 
162 static 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 
172 static 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 
198 static 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 
228 static 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 
234 static const struct watchdog_info dw_wdt_ident = {
235         .options        = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
236                           WDIOF_MAGICCLOSE,
237         .identity       = "Synopsys DesignWare Watchdog",
238 };
239 
240 static 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 
278 static 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
297 static int dw_wdt_suspend(struct device *dev)
298 {
299         clk_disable_unprepare(dw_wdt.clk);
300 
301         return 0;
302 }
303 
304 static 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 
317 static SIMPLE_DEV_PM_OPS(dw_wdt_pm_ops, dw_wdt_suspend, dw_wdt_resume);
318 
319 static 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 
328 static struct miscdevice dw_wdt_miscdev = {
329         .fops           = &wdt_fops,
330         .name           = "watchdog",
331         .minor          = WATCHDOG_MINOR,
332 };
333 
334 static 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 
369 out_disable_clk:
370         clk_disable_unprepare(dw_wdt.clk);
371 
372         return ret;
373 }
374 
375 static 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
387 static const struct of_device_id dw_wdt_of_match[] = {
388         { .compatible = "snps,dw-wdt", },
389         { /* sentinel */ }
390 };
391 MODULE_DEVICE_TABLE(of, dw_wdt_of_match);
392 #endif
393 
394 static 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 
404 module_platform_driver(dw_wdt_driver);
405 
406 MODULE_AUTHOR("Jamie Iles");
407 MODULE_DESCRIPTION("Synopsys DesignWare Watchdog Driver");
408 MODULE_LICENSE("GPL");
409 

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