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Linux/drivers/watchdog/nuc900_wdt.c

  1 /*
  2  * Copyright (c) 2009 Nuvoton technology corporation.
  3  *
  4  * Wan ZongShun <mcuos.com@gmail.com>
  5  *
  6  * This program is free software; you can redistribute it and/or modify
  7  * it under the terms of the GNU General Public License as published by
  8  * the Free Software Foundation;version 2 of the License.
  9  *
 10  */
 11 
 12 #include <linux/bitops.h>
 13 #include <linux/errno.h>
 14 #include <linux/fs.h>
 15 #include <linux/io.h>
 16 #include <linux/clk.h>
 17 #include <linux/kernel.h>
 18 #include <linux/miscdevice.h>
 19 #include <linux/module.h>
 20 #include <linux/moduleparam.h>
 21 #include <linux/platform_device.h>
 22 #include <linux/slab.h>
 23 #include <linux/interrupt.h>
 24 #include <linux/types.h>
 25 #include <linux/watchdog.h>
 26 #include <linux/uaccess.h>
 27 
 28 #define REG_WTCR                0x1c
 29 #define WTCLK                   (0x01 << 10)
 30 #define WTE                     (0x01 << 7)     /*wdt enable*/
 31 #define WTIS                    (0x03 << 4)
 32 #define WTIF                    (0x01 << 3)
 33 #define WTRF                    (0x01 << 2)
 34 #define WTRE                    (0x01 << 1)
 35 #define WTR                     (0x01 << 0)
 36 /*
 37  * The watchdog time interval can be calculated via following formula:
 38  * WTIS         real time interval (formula)
 39  * 0x00         ((2^ 14 ) * ((external crystal freq) / 256))seconds
 40  * 0x01         ((2^ 16 ) * ((external crystal freq) / 256))seconds
 41  * 0x02         ((2^ 18 ) * ((external crystal freq) / 256))seconds
 42  * 0x03         ((2^ 20 ) * ((external crystal freq) / 256))seconds
 43  *
 44  * The external crystal freq is 15Mhz in the nuc900 evaluation board.
 45  * So 0x00 = +-0.28 seconds, 0x01 = +-1.12 seconds, 0x02 = +-4.48 seconds,
 46  * 0x03 = +- 16.92 seconds..
 47  */
 48 #define WDT_HW_TIMEOUT          0x02
 49 #define WDT_TIMEOUT             (HZ/2)
 50 #define WDT_HEARTBEAT           15
 51 
 52 static int heartbeat = WDT_HEARTBEAT;
 53 module_param(heartbeat, int, 0);
 54 MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds. "
 55         "(default = " __MODULE_STRING(WDT_HEARTBEAT) ")");
 56 
 57 static bool nowayout = WATCHDOG_NOWAYOUT;
 58 module_param(nowayout, bool, 0);
 59 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
 60         "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
 61 
 62 struct nuc900_wdt {
 63         struct clk       *wdt_clock;
 64         struct platform_device *pdev;
 65         void __iomem     *wdt_base;
 66         char             expect_close;
 67         struct timer_list timer;
 68         spinlock_t       wdt_lock;
 69         unsigned long next_heartbeat;
 70 };
 71 
 72 static unsigned long nuc900wdt_busy;
 73 static struct nuc900_wdt *nuc900_wdt;
 74 
 75 static inline void nuc900_wdt_keepalive(void)
 76 {
 77         unsigned int val;
 78 
 79         spin_lock(&nuc900_wdt->wdt_lock);
 80 
 81         val = __raw_readl(nuc900_wdt->wdt_base + REG_WTCR);
 82         val |= (WTR | WTIF);
 83         __raw_writel(val, nuc900_wdt->wdt_base + REG_WTCR);
 84 
 85         spin_unlock(&nuc900_wdt->wdt_lock);
 86 }
 87 
 88 static inline void nuc900_wdt_start(void)
 89 {
 90         unsigned int val;
 91 
 92         spin_lock(&nuc900_wdt->wdt_lock);
 93 
 94         val = __raw_readl(nuc900_wdt->wdt_base + REG_WTCR);
 95         val |= (WTRE | WTE | WTR | WTCLK | WTIF);
 96         val &= ~WTIS;
 97         val |= (WDT_HW_TIMEOUT << 0x04);
 98         __raw_writel(val, nuc900_wdt->wdt_base + REG_WTCR);
 99 
100         spin_unlock(&nuc900_wdt->wdt_lock);
101 
102         nuc900_wdt->next_heartbeat = jiffies + heartbeat * HZ;
103         mod_timer(&nuc900_wdt->timer, jiffies + WDT_TIMEOUT);
104 }
105 
106 static inline void nuc900_wdt_stop(void)
107 {
108         unsigned int val;
109 
110         del_timer(&nuc900_wdt->timer);
111 
112         spin_lock(&nuc900_wdt->wdt_lock);
113 
114         val = __raw_readl(nuc900_wdt->wdt_base + REG_WTCR);
115         val &= ~WTE;
116         __raw_writel(val, nuc900_wdt->wdt_base + REG_WTCR);
117 
118         spin_unlock(&nuc900_wdt->wdt_lock);
119 }
120 
121 static inline void nuc900_wdt_ping(void)
122 {
123         nuc900_wdt->next_heartbeat = jiffies + heartbeat * HZ;
124 }
125 
126 static int nuc900_wdt_open(struct inode *inode, struct file *file)
127 {
128 
129         if (test_and_set_bit(0, &nuc900wdt_busy))
130                 return -EBUSY;
131 
132         nuc900_wdt_start();
133 
134         return nonseekable_open(inode, file);
135 }
136 
137 static int nuc900_wdt_close(struct inode *inode, struct file *file)
138 {
139         if (nuc900_wdt->expect_close == 42)
140                 nuc900_wdt_stop();
141         else {
142                 dev_crit(&nuc900_wdt->pdev->dev,
143                         "Unexpected close, not stopping watchdog!\n");
144                 nuc900_wdt_ping();
145         }
146 
147         nuc900_wdt->expect_close = 0;
148         clear_bit(0, &nuc900wdt_busy);
149         return 0;
150 }
151 
152 static const struct watchdog_info nuc900_wdt_info = {
153         .identity       = "nuc900 watchdog",
154         .options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
155                                                 WDIOF_MAGICCLOSE,
156 };
157 
158 static long nuc900_wdt_ioctl(struct file *file,
159                                         unsigned int cmd, unsigned long arg)
160 {
161         void __user *argp = (void __user *)arg;
162         int __user *p = argp;
163         int new_value;
164 
165         switch (cmd) {
166         case WDIOC_GETSUPPORT:
167                 return copy_to_user(argp, &nuc900_wdt_info,
168                                 sizeof(nuc900_wdt_info)) ? -EFAULT : 0;
169         case WDIOC_GETSTATUS:
170         case WDIOC_GETBOOTSTATUS:
171                 return put_user(0, p);
172 
173         case WDIOC_KEEPALIVE:
174                 nuc900_wdt_ping();
175                 return 0;
176 
177         case WDIOC_SETTIMEOUT:
178                 if (get_user(new_value, p))
179                         return -EFAULT;
180 
181                 heartbeat = new_value;
182                 nuc900_wdt_ping();
183 
184                 return put_user(new_value, p);
185         case WDIOC_GETTIMEOUT:
186                 return put_user(heartbeat, p);
187         default:
188                 return -ENOTTY;
189         }
190 }
191 
192 static ssize_t nuc900_wdt_write(struct file *file, const char __user *data,
193                                                 size_t len, loff_t *ppos)
194 {
195         if (!len)
196                 return 0;
197 
198         /* Scan for magic character */
199         if (!nowayout) {
200                 size_t i;
201 
202                 nuc900_wdt->expect_close = 0;
203 
204                 for (i = 0; i < len; i++) {
205                         char c;
206                         if (get_user(c, data + i))
207                                 return -EFAULT;
208                         if (c == 'V') {
209                                 nuc900_wdt->expect_close = 42;
210                                 break;
211                         }
212                 }
213         }
214 
215         nuc900_wdt_ping();
216         return len;
217 }
218 
219 static void nuc900_wdt_timer_ping(unsigned long data)
220 {
221         if (time_before(jiffies, nuc900_wdt->next_heartbeat)) {
222                 nuc900_wdt_keepalive();
223                 mod_timer(&nuc900_wdt->timer, jiffies + WDT_TIMEOUT);
224         } else
225                 dev_warn(&nuc900_wdt->pdev->dev, "Will reset the machine !\n");
226 }
227 
228 static const struct file_operations nuc900wdt_fops = {
229         .owner          = THIS_MODULE,
230         .llseek         = no_llseek,
231         .unlocked_ioctl = nuc900_wdt_ioctl,
232         .open           = nuc900_wdt_open,
233         .release        = nuc900_wdt_close,
234         .write          = nuc900_wdt_write,
235 };
236 
237 static struct miscdevice nuc900wdt_miscdev = {
238         .minor          = WATCHDOG_MINOR,
239         .name           = "watchdog",
240         .fops           = &nuc900wdt_fops,
241 };
242 
243 static int nuc900wdt_probe(struct platform_device *pdev)
244 {
245         struct resource *res;
246         int ret = 0;
247 
248         nuc900_wdt = devm_kzalloc(&pdev->dev, sizeof(*nuc900_wdt),
249                                 GFP_KERNEL);
250         if (!nuc900_wdt)
251                 return -ENOMEM;
252 
253         nuc900_wdt->pdev = pdev;
254 
255         spin_lock_init(&nuc900_wdt->wdt_lock);
256 
257         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
258         nuc900_wdt->wdt_base = devm_ioremap_resource(&pdev->dev, res);
259         if (IS_ERR(nuc900_wdt->wdt_base))
260                 return PTR_ERR(nuc900_wdt->wdt_base);
261 
262         nuc900_wdt->wdt_clock = devm_clk_get(&pdev->dev, NULL);
263         if (IS_ERR(nuc900_wdt->wdt_clock)) {
264                 dev_err(&pdev->dev, "failed to find watchdog clock source\n");
265                 return PTR_ERR(nuc900_wdt->wdt_clock);
266         }
267 
268         clk_enable(nuc900_wdt->wdt_clock);
269 
270         setup_timer(&nuc900_wdt->timer, nuc900_wdt_timer_ping, 0);
271 
272         ret = misc_register(&nuc900wdt_miscdev);
273         if (ret) {
274                 dev_err(&pdev->dev, "err register miscdev on minor=%d (%d)\n",
275                         WATCHDOG_MINOR, ret);
276                 goto err_clk;
277         }
278 
279         return 0;
280 
281 err_clk:
282         clk_disable(nuc900_wdt->wdt_clock);
283         return ret;
284 }
285 
286 static int nuc900wdt_remove(struct platform_device *pdev)
287 {
288         misc_deregister(&nuc900wdt_miscdev);
289 
290         clk_disable(nuc900_wdt->wdt_clock);
291 
292         return 0;
293 }
294 
295 static struct platform_driver nuc900wdt_driver = {
296         .probe          = nuc900wdt_probe,
297         .remove         = nuc900wdt_remove,
298         .driver         = {
299                 .name   = "nuc900-wdt",
300                 .owner  = THIS_MODULE,
301         },
302 };
303 
304 module_platform_driver(nuc900wdt_driver);
305 
306 MODULE_AUTHOR("Wan ZongShun <mcuos.com@gmail.com>");
307 MODULE_DESCRIPTION("Watchdog driver for NUC900");
308 MODULE_LICENSE("GPL");
309 MODULE_ALIAS("platform:nuc900-wdt");
310 

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