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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 | ssize_t dw_wdt_write(struct file *filp, const char __user *buf, size_t len, |
158 | 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((struct watchdog_info *)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 *)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 |
256 | static int dw_wdt_suspend(struct device *dev) |
257 | { |
258 | clk_disable(dw_wdt.clk); |
259 | |
260 | return 0; |
261 | } |
262 | |
263 | static int dw_wdt_resume(struct device *dev) |
264 | { |
265 | int err = clk_enable(dw_wdt.clk); |
266 | |
267 | if (err) |
268 | return err; |
269 | |
270 | dw_wdt_keepalive(); |
271 | |
272 | return 0; |
273 | } |
274 | |
275 | static const struct dev_pm_ops dw_wdt_pm_ops = { |
276 | .suspend = dw_wdt_suspend, |
277 | .resume = dw_wdt_resume, |
278 | }; |
279 | #endif /* CONFIG_PM */ |
280 | |
281 | static const struct file_operations wdt_fops = { |
282 | .owner = THIS_MODULE, |
283 | .llseek = no_llseek, |
284 | .open = dw_wdt_open, |
285 | .write = dw_wdt_write, |
286 | .unlocked_ioctl = dw_wdt_ioctl, |
287 | .release = dw_wdt_release |
288 | }; |
289 | |
290 | static struct miscdevice dw_wdt_miscdev = { |
291 | .fops = &wdt_fops, |
292 | .name = "watchdog", |
293 | .minor = WATCHDOG_MINOR, |
294 | }; |
295 | |
296 | static int dw_wdt_drv_probe(struct platform_device *pdev) |
297 | { |
298 | int ret; |
299 | struct resource *mem = platform_get_resource(pdev, IORESOURCE_MEM, 0); |
300 | |
301 | if (!mem) |
302 | return -EINVAL; |
303 | |
304 | dw_wdt.regs = devm_ioremap_resource(&pdev->dev, mem); |
305 | if (IS_ERR(dw_wdt.regs)) |
306 | return PTR_ERR(dw_wdt.regs); |
307 | |
308 | dw_wdt.clk = clk_get(&pdev->dev, NULL); |
309 | if (IS_ERR(dw_wdt.clk)) |
310 | return PTR_ERR(dw_wdt.clk); |
311 | |
312 | ret = clk_enable(dw_wdt.clk); |
313 | if (ret) |
314 | goto out_put_clk; |
315 | |
316 | spin_lock_init(&dw_wdt.lock); |
317 | |
318 | ret = misc_register(&dw_wdt_miscdev); |
319 | if (ret) |
320 | goto out_disable_clk; |
321 | |
322 | dw_wdt_set_next_heartbeat(); |
323 | setup_timer(&dw_wdt.timer, dw_wdt_ping, 0); |
324 | mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT); |
325 | |
326 | return 0; |
327 | |
328 | out_disable_clk: |
329 | clk_disable(dw_wdt.clk); |
330 | out_put_clk: |
331 | clk_put(dw_wdt.clk); |
332 | |
333 | return ret; |
334 | } |
335 | |
336 | static int dw_wdt_drv_remove(struct platform_device *pdev) |
337 | { |
338 | misc_deregister(&dw_wdt_miscdev); |
339 | |
340 | clk_disable(dw_wdt.clk); |
341 | clk_put(dw_wdt.clk); |
342 | |
343 | return 0; |
344 | } |
345 | |
346 | static struct platform_driver dw_wdt_driver = { |
347 | .probe = dw_wdt_drv_probe, |
348 | .remove = dw_wdt_drv_remove, |
349 | .driver = { |
350 | .name = "dw_wdt", |
351 | .owner = THIS_MODULE, |
352 | #ifdef CONFIG_PM |
353 | .pm = &dw_wdt_pm_ops, |
354 | #endif /* CONFIG_PM */ |
355 | }, |
356 | }; |
357 | |
358 | module_platform_driver(dw_wdt_driver); |
359 | |
360 | MODULE_AUTHOR("Jamie Iles"); |
361 | MODULE_DESCRIPTION("Synopsys DesignWare Watchdog Driver"); |
362 | MODULE_LICENSE("GPL"); |
363 | MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR); |
364 |
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