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 #define pr_fmt(fmt) "dw_wdt: " fmt
  20
  21 #include <linux/bitops.h>
  22 #include <linux/clk.h>
  23 #include <linux/device.h>
  24 #include <linux/err.h>
  25 #include <linux/fs.h>
  26 #include <linux/io.h>
  27 #include <linux/kernel.h>
  28 #include <linux/miscdevice.h>
  29 #include <linux/module.h>
  30 #include <linux/moduleparam.h>
  31 #include <linux/pm.h>
  32 #include <linux/platform_device.h>
  33 #include <linux/spinlock.h>
  34 #include <linux/timer.h>
  35 #include <linux/uaccess.h>
  36 #include <linux/watchdog.h>
  37
  38 #define WDOG_CONTROL_REG_OFFSET             0x00
  39 #define WDOG_CONTROL_REG_WDT_EN_MASK        0x01
  40 #define WDOG_TIMEOUT_RANGE_REG_OFFSET       0x04
  41 #define WDOG_CURRENT_COUNT_REG_OFFSET       0x08
  42 #define WDOG_COUNTER_RESTART_REG_OFFSET     0x0c
  43 #define WDOG_COUNTER_RESTART_KICK_VALUE     0x76
  44
  45 /* The maximum TOP (timeout period) value that can be set in the watchdog. */
  46 #define DW_WDT_MAX_TOP          15
  47
  48 static int nowayout = WATCHDOG_NOWAYOUT;
  49 module_param(nowayout, int, 0);
  50 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
  51                  "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  52
  53 #define WDT_TIMEOUT             (HZ / 2)
  54
  55 static struct {
  56         spinlock_t              lock;
  57         void __iomem            *regs;
  58         struct clk              *clk;
  59         unsigned long           in_use;
  60         unsigned long           next_heartbeat;
  61         struct timer_list       timer;
  62         int                     expect_close;
  63 } dw_wdt;
  64
  65 static inline int dw_wdt_is_enabled(void)
  66 {
  67         return readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET) &
  68                 WDOG_CONTROL_REG_WDT_EN_MASK;
  69 }
  70
  71 static inline int dw_wdt_top_in_seconds(unsigned top)
  72 {
  73         /*
  74          * There are 16 possible timeout values in 0..15 where the number of
  75          * cycles is 2 ^ (16 + i) and the watchdog counts down.
  76          */
  77         return (1 << (16 + top)) / clk_get_rate(dw_wdt.clk);
  78 }
  79
  80 static int dw_wdt_get_top(void)
  81 {
  82         int top = readl(dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET) & 0xF;
  83
  84         return dw_wdt_top_in_seconds(top);
  85 }
  86
  87 static inline void dw_wdt_set_next_heartbeat(void)
  88 {
  89         dw_wdt.next_heartbeat = jiffies + dw_wdt_get_top() * HZ;
  90 }
  91
  92 static int dw_wdt_set_top(unsigned top_s)
  93 {
  94         int i, top_val = DW_WDT_MAX_TOP;
  95
  96         /*
  97          * Iterate over the timeout values until we find the closest match. We
  98          * always look for >=.
  99          */
 100         for (i = 0; i <= DW_WDT_MAX_TOP; ++i)
 101                 if (dw_wdt_top_in_seconds(i) >= top_s) {
 102                         top_val = i;
 103                         break;
 104                 }
 105
 106         /* Set the new value in the watchdog. */
 107         writel(top_val, dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);
 108
 109         dw_wdt_set_next_heartbeat();
 110
 111         return dw_wdt_top_in_seconds(top_val);
 112 }
 113
 114 static void dw_wdt_keepalive(void)
 115 {
 116         writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
 117                WDOG_COUNTER_RESTART_REG_OFFSET);
 118 }
 119
 120 static void dw_wdt_ping(unsigned long data)
 121 {
 122         if (time_before(jiffies, dw_wdt.next_heartbeat) ||
 123             (!nowayout && !dw_wdt.in_use)) {
 124                 dw_wdt_keepalive();
 125                 mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
 126         } else
 127                 pr_crit("keepalive missed, machine will reset\n");
 128 }
 129
 130 static int dw_wdt_open(struct inode *inode, struct file *filp)
 131 {
 132         if (test_and_set_bit(0, &dw_wdt.in_use))
 133                 return -EBUSY;
 134
 135         /* Make sure we don't get unloaded. */
 136         __module_get(THIS_MODULE);
 137
 138         spin_lock(&dw_wdt.lock);
 139         if (!dw_wdt_is_enabled()) {
 140                 /*
 141                  * The watchdog is not currently enabled. Set the timeout to
 142                  * the maximum and then start it.
 143                  */
 144                 dw_wdt_set_top(DW_WDT_MAX_TOP);
 145                 writel(WDOG_CONTROL_REG_WDT_EN_MASK,
 146                        dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
 147         }
 148
 149         dw_wdt_set_next_heartbeat();
 150
 151         spin_unlock(&dw_wdt.lock);
 152
 153         return nonseekable_open(inode, filp);
 154 }
 155
 156 ssize_t dw_wdt_write(struct file *filp, const char __user *buf, size_t len,
 157                      loff_t *offset)
 158 {
 159         if (!len)
 160                 return 0;
 161
 162         if (!nowayout) {
 163                 size_t i;
 164
 165                 dw_wdt.expect_close = 0;
 166
 167                 for (i = 0; i < len; ++i) {
 168                         char c;
 169
 170                         if (get_user(c, buf + i))
 171                                 return -EFAULT;
 172
 173                         if (c == 'V') {
 174                                 dw_wdt.expect_close = 1;
 175                                 break;
 176                         }
 177                 }
 178         }
 179
 180         dw_wdt_set_next_heartbeat();
 181         mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
 182
 183         return len;
 184 }
 185
 186 static u32 dw_wdt_time_left(void)
 187 {
 188         return readl(dw_wdt.regs + WDOG_CURRENT_COUNT_REG_OFFSET) /
 189                 clk_get_rate(dw_wdt.clk);
 190 }
 191
 192 static const struct watchdog_info dw_wdt_ident = {
 193         .options        = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
 194                           WDIOF_MAGICCLOSE,
 195         .identity       = "Synopsys DesignWare Watchdog",
 196 };
 197
 198 static long dw_wdt_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 199 {
 200         unsigned long val;
 201         int timeout;
 202
 203         switch (cmd) {
 204         case WDIOC_GETSUPPORT:
 205                 return copy_to_user((struct watchdog_info *)arg, &dw_wdt_ident,
 206                                     sizeof(dw_wdt_ident)) ? -EFAULT : 0;
 207
 208         case WDIOC_GETSTATUS:
 209         case WDIOC_GETBOOTSTATUS:
 210                 return put_user(0, (int *)arg);
 211
 212         case WDIOC_KEEPALIVE:
 213                 dw_wdt_set_next_heartbeat();
 214                 return 0;
 215
 216         case WDIOC_SETTIMEOUT:
 217                 if (get_user(val, (int __user *)arg))
 218                         return -EFAULT;
 219                 timeout = dw_wdt_set_top(val);
 220                 return put_user(timeout , (int __user *)arg);
 221
 222         case WDIOC_GETTIMEOUT:
 223                 return put_user(dw_wdt_get_top(), (int __user *)arg);
 224
 225         case WDIOC_GETTIMELEFT:
 226                 /* Get the time left until expiry. */
 227                 if (get_user(val, (int __user *)arg))
 228                         return -EFAULT;
 229                 return put_user(dw_wdt_time_left(), (int __user *)arg);
 230
 231         default:
 232                 return -ENOTTY;
 233         }
 234 }
 235
 236 static int dw_wdt_release(struct inode *inode, struct file *filp)
 237 {
 238         clear_bit(0, &dw_wdt.in_use);
 239
 240         if (!dw_wdt.expect_close) {
 241                 del_timer(&dw_wdt.timer);
 242
 243                 if (!nowayout)
 244                         pr_crit("unexpected close, system will reboot soon\n");
 245                 else
 246                         pr_crit("watchdog cannot be disabled, system will reboot soon\n");
 247         }
 248
 249         dw_wdt.expect_close = 0;
 250
 251         return 0;
 252 }
 253
 254 #ifdef CONFIG_PM
 255 static int dw_wdt_suspend(struct device *dev)
 256 {
 257         clk_disable(dw_wdt.clk);
 258
 259         return 0;
 260 }
 261
 262 static int dw_wdt_resume(struct device *dev)
 263 {
 264         int err = clk_enable(dw_wdt.clk);
 265
 266         if (err)
 267                 return err;
 268
 269         dw_wdt_keepalive();
 270
 271         return 0;
 272 }
 273
 274 static const struct dev_pm_ops dw_wdt_pm_ops = {
 275         .suspend        = dw_wdt_suspend,
 276         .resume         = dw_wdt_resume,
 277 };
 278 #endif /* CONFIG_PM */
 279
 280 static const struct file_operations wdt_fops = {
 281         .owner          = THIS_MODULE,
 282         .llseek         = no_llseek,
 283         .open           = dw_wdt_open,
 284         .write          = dw_wdt_write,
 285         .unlocked_ioctl = dw_wdt_ioctl,
 286         .release        = dw_wdt_release
 287 };
 288
 289 static struct miscdevice dw_wdt_miscdev = {
 290         .fops           = &wdt_fops,
 291         .name           = "watchdog",
 292         .minor          = WATCHDOG_MINOR,
 293 };
 294
 295 static int __devinit dw_wdt_drv_probe(struct platform_device *pdev)
 296 {
 297         int ret;
 298         struct resource *mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 299
 300         if (!mem)
 301                 return -EINVAL;
 302
 303         dw_wdt.regs = devm_request_and_ioremap(&pdev->dev, mem);
 304         if (!dw_wdt.regs)
 305                 return -ENOMEM;
 306
 307         dw_wdt.clk = clk_get(&pdev->dev, NULL);
 308         if (IS_ERR(dw_wdt.clk))
 309                 return PTR_ERR(dw_wdt.clk);
 310
 311         ret = clk_enable(dw_wdt.clk);
 312         if (ret)
 313                 goto out_put_clk;
 314
 315         spin_lock_init(&dw_wdt.lock);
 316
 317         ret = misc_register(&dw_wdt_miscdev);
 318         if (ret)
 319                 goto out_disable_clk;
 320
 321         dw_wdt_set_next_heartbeat();
 322         setup_timer(&dw_wdt.timer, dw_wdt_ping, 0);
 323         mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
 324
 325         return 0;
 326
 327 out_disable_clk:
 328         clk_disable(dw_wdt.clk);
 329 out_put_clk:
 330         clk_put(dw_wdt.clk);
 331
 332         return ret;
 333 }
 334
 335 static int __devexit dw_wdt_drv_remove(struct platform_device *pdev)
 336 {
 337         misc_deregister(&dw_wdt_miscdev);
 338
 339         clk_disable(dw_wdt.clk);
 340         clk_put(dw_wdt.clk);
 341
 342         return 0;
 343 }
 344
 345 static struct platform_driver dw_wdt_driver = {
 346         .probe          = dw_wdt_drv_probe,
 347         .remove         = __devexit_p(dw_wdt_drv_remove),
 348         .driver         = {
 349                 .name   = "dw_wdt",
 350                 .owner  = THIS_MODULE,
 351 #ifdef CONFIG_PM
 352                 .pm     = &dw_wdt_pm_ops,
 353 #endif /* CONFIG_PM */
 354         },
 355 };
 356
 357 module_platform_driver(dw_wdt_driver);
 358
 359 MODULE_AUTHOR("Jamie Iles");
 360 MODULE_DESCRIPTION("Synopsys DesignWare Watchdog Driver");
 361 MODULE_LICENSE("GPL");
 362 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);