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/timer.h>
  39 #include <linux/uaccess.h>
  40 #include <linux/watchdog.h>
  41
  42 #define WDOG_CONTROL_REG_OFFSET             0x00
  43 #define WDOG_CONTROL_REG_WDT_EN_MASK        0x01
  44 #define WDOG_TIMEOUT_RANGE_REG_OFFSET       0x04
  45 #define WDOG_TIMEOUT_RANGE_TOPINIT_SHIFT    4
  46 #define WDOG_CURRENT_COUNT_REG_OFFSET       0x08
  47 #define WDOG_COUNTER_RESTART_REG_OFFSET     0x0c
  48 #define WDOG_COUNTER_RESTART_KICK_VALUE     0x76
  49
  50 /* The maximum TOP (timeout period) value that can be set in the watchdog. */
  51 #define DW_WDT_MAX_TOP          15
  52
  53 #define DW_WDT_DEFAULT_SECONDS  30
  54
  55 static bool nowayout = WATCHDOG_NOWAYOUT;
  56 module_param(nowayout, bool, 0);
  57 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
  58                  "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  59
  60 #define WDT_TIMEOUT             (HZ / 2)
  61
  62 static struct {
  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 void dw_wdt_keepalive(void)
 100 {
 101         writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
 102                WDOG_COUNTER_RESTART_REG_OFFSET);
 103 }
 104
 105 static int dw_wdt_set_top(unsigned top_s)
 106 {
 107         int i, top_val = DW_WDT_MAX_TOP;
 108
 109         /*
 110          * Iterate over the timeout values until we find the closest match. We
 111          * always look for >=.
 112          */
 113         for (i = 0; i <= DW_WDT_MAX_TOP; ++i)
 114                 if (dw_wdt_top_in_seconds(i) >= top_s) {
 115                         top_val = i;
 116                         break;
 117                 }
 118
 119         /*
 120          * Set the new value in the watchdog.  Some versions of dw_wdt
 121          * have have TOPINIT in the TIMEOUT_RANGE register (as per
 122          * CP_WDT_DUAL_TOP in WDT_COMP_PARAMS_1).  On those we
 123          * effectively get a pat of the watchdog right here.
 124          */
 125         writel(top_val | top_val << WDOG_TIMEOUT_RANGE_TOPINIT_SHIFT,
 126                 dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);
 127
 128         /*
 129          * Add an explicit pat to handle versions of the watchdog that
 130          * don't have TOPINIT.  This won't hurt on versions that have
 131          * it.
 132          */
 133         dw_wdt_keepalive();
 134
 135         dw_wdt_set_next_heartbeat();
 136
 137         return dw_wdt_top_in_seconds(top_val);
 138 }
 139
 140 static int dw_wdt_restart_handle(struct notifier_block *this,
 141                                 unsigned long mode, void *cmd)
 142 {
 143         u32 val;
 144
 145         writel(0, dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);
 146         val = readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
 147         if (val & WDOG_CONTROL_REG_WDT_EN_MASK)
 148                 writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
 149                         WDOG_COUNTER_RESTART_REG_OFFSET);
 150         else
 151                 writel(WDOG_CONTROL_REG_WDT_EN_MASK,
 152                        dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
 153
 154         /* wait for reset to assert... */
 155         mdelay(500);
 156
 157         return NOTIFY_DONE;
 158 }
 159
 160 static void dw_wdt_ping(unsigned long data)
 161 {
 162         if (time_before(jiffies, dw_wdt.next_heartbeat) ||
 163             (!nowayout && !dw_wdt.in_use)) {
 164                 dw_wdt_keepalive();
 165                 mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
 166         } else
 167                 pr_crit("keepalive missed, machine will reset\n");
 168 }
 169
 170 static int dw_wdt_open(struct inode *inode, struct file *filp)
 171 {
 172         if (test_and_set_bit(0, &dw_wdt.in_use))
 173                 return -EBUSY;
 174
 175         /* Make sure we don't get unloaded. */
 176         __module_get(THIS_MODULE);
 177
 178         if (!dw_wdt_is_enabled()) {
 179                 /*
 180                  * The watchdog is not currently enabled. Set the timeout to
 181                  * something reasonable and then start it.
 182                  */
 183                 dw_wdt_set_top(DW_WDT_DEFAULT_SECONDS);
 184                 writel(WDOG_CONTROL_REG_WDT_EN_MASK,
 185                        dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
 186         }
 187
 188         dw_wdt_set_next_heartbeat();
 189
 190         return nonseekable_open(inode, filp);
 191 }
 192
 193 static ssize_t dw_wdt_write(struct file *filp, const char __user *buf,
 194                             size_t len, loff_t *offset)
 195 {
 196         if (!len)
 197                 return 0;
 198
 199         if (!nowayout) {
 200                 size_t i;
 201
 202                 dw_wdt.expect_close = 0;
 203
 204                 for (i = 0; i < len; ++i) {
 205                         char c;
 206
 207                         if (get_user(c, buf + i))
 208                                 return -EFAULT;
 209
 210                         if (c == 'V') {
 211                                 dw_wdt.expect_close = 1;
 212                                 break;
 213                         }
 214                 }
 215         }
 216
 217         dw_wdt_set_next_heartbeat();
 218         dw_wdt_keepalive();
 219         mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
 220
 221         return len;
 222 }
 223
 224 static u32 dw_wdt_time_left(void)
 225 {
 226         return readl(dw_wdt.regs + WDOG_CURRENT_COUNT_REG_OFFSET) /
 227                 clk_get_rate(dw_wdt.clk);
 228 }
 229
 230 static const struct watchdog_info dw_wdt_ident = {
 231         .options        = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
 232                           WDIOF_MAGICCLOSE,
 233         .identity       = "Synopsys DesignWare Watchdog",
 234 };
 235
 236 static long dw_wdt_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 237 {
 238         unsigned long val;
 239         int timeout;
 240
 241         switch (cmd) {
 242         case WDIOC_GETSUPPORT:
 243                 return copy_to_user((void __user *)arg, &dw_wdt_ident,
 244                                     sizeof(dw_wdt_ident)) ? -EFAULT : 0;
 245
 246         case WDIOC_GETSTATUS:
 247         case WDIOC_GETBOOTSTATUS:
 248                 return put_user(0, (int __user *)arg);
 249
 250         case WDIOC_KEEPALIVE:
 251                 dw_wdt_set_next_heartbeat();
 252                 return 0;
 253
 254         case WDIOC_SETTIMEOUT:
 255                 if (get_user(val, (int __user *)arg))
 256                         return -EFAULT;
 257                 timeout = dw_wdt_set_top(val);
 258                 return put_user(timeout , (int __user *)arg);
 259
 260         case WDIOC_GETTIMEOUT:
 261                 return put_user(dw_wdt_get_top(), (int __user *)arg);
 262
 263         case WDIOC_GETTIMELEFT:
 264                 /* Get the time left until expiry. */
 265                 if (get_user(val, (int __user *)arg))
 266                         return -EFAULT;
 267                 return put_user(dw_wdt_time_left(), (int __user *)arg);
 268
 269         default:
 270                 return -ENOTTY;
 271         }
 272 }
 273
 274 static int dw_wdt_release(struct inode *inode, struct file *filp)
 275 {
 276         clear_bit(0, &dw_wdt.in_use);
 277
 278         if (!dw_wdt.expect_close) {
 279                 del_timer(&dw_wdt.timer);
 280
 281                 if (!nowayout)
 282                         pr_crit("unexpected close, system will reboot soon\n");
 283                 else
 284                         pr_crit("watchdog cannot be disabled, system will reboot soon\n");
 285         }
 286
 287         dw_wdt.expect_close = 0;
 288
 289         return 0;
 290 }
 291
 292 #ifdef CONFIG_PM_SLEEP
 293 static int dw_wdt_suspend(struct device *dev)
 294 {
 295         clk_disable_unprepare(dw_wdt.clk);
 296
 297         return 0;
 298 }
 299
 300 static int dw_wdt_resume(struct device *dev)
 301 {
 302         int err = clk_prepare_enable(dw_wdt.clk);
 303
 304         if (err)
 305                 return err;
 306
 307         dw_wdt_keepalive();
 308
 309         return 0;
 310 }
 311 #endif /* CONFIG_PM_SLEEP */
 312
 313 static SIMPLE_DEV_PM_OPS(dw_wdt_pm_ops, dw_wdt_suspend, dw_wdt_resume);
 314
 315 static const struct file_operations wdt_fops = {
 316         .owner          = THIS_MODULE,
 317         .llseek         = no_llseek,
 318         .open           = dw_wdt_open,
 319         .write          = dw_wdt_write,
 320         .unlocked_ioctl = dw_wdt_ioctl,
 321         .release        = dw_wdt_release
 322 };
 323
 324 static struct miscdevice dw_wdt_miscdev = {
 325         .fops           = &wdt_fops,
 326         .name           = "watchdog",
 327         .minor          = WATCHDOG_MINOR,
 328 };
 329
 330 static int dw_wdt_drv_probe(struct platform_device *pdev)
 331 {
 332         int ret;
 333         struct resource *mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 334
 335         dw_wdt.regs = devm_ioremap_resource(&pdev->dev, mem);
 336         if (IS_ERR(dw_wdt.regs))
 337                 return PTR_ERR(dw_wdt.regs);
 338
 339         dw_wdt.clk = devm_clk_get(&pdev->dev, NULL);
 340         if (IS_ERR(dw_wdt.clk))
 341                 return PTR_ERR(dw_wdt.clk);
 342
 343         ret = clk_prepare_enable(dw_wdt.clk);
 344         if (ret)
 345                 return ret;
 346
 347         ret = misc_register(&dw_wdt_miscdev);
 348         if (ret)
 349                 goto out_disable_clk;
 350
 351         dw_wdt.restart_handler.notifier_call = dw_wdt_restart_handle;
 352         dw_wdt.restart_handler.priority = 128;
 353         ret = register_restart_handler(&dw_wdt.restart_handler);
 354         if (ret)
 355                 pr_warn("cannot register restart handler\n");
 356
 357         dw_wdt_set_next_heartbeat();
 358         setup_timer(&dw_wdt.timer, dw_wdt_ping, 0);
 359         mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
 360
 361         return 0;
 362
 363 out_disable_clk:
 364         clk_disable_unprepare(dw_wdt.clk);
 365
 366         return ret;
 367 }
 368
 369 static int dw_wdt_drv_remove(struct platform_device *pdev)
 370 {
 371         unregister_restart_handler(&dw_wdt.restart_handler);
 372
 373         misc_deregister(&dw_wdt_miscdev);
 374
 375         clk_disable_unprepare(dw_wdt.clk);
 376
 377         return 0;
 378 }
 379
 380 #ifdef CONFIG_OF
 381 static const struct of_device_id dw_wdt_of_match[] = {
 382         { .compatible = "snps,dw-wdt", },
 383         { /* sentinel */ }
 384 };
 385 MODULE_DEVICE_TABLE(of, dw_wdt_of_match);
 386 #endif
 387
 388 static struct platform_driver dw_wdt_driver = {
 389         .probe          = dw_wdt_drv_probe,
 390         .remove         = dw_wdt_drv_remove,
 391         .driver         = {
 392                 .name   = "dw_wdt",
 393                 .of_match_table = of_match_ptr(dw_wdt_of_match),
 394                 .pm     = &dw_wdt_pm_ops,
 395         },
 396 };
 397
 398 module_platform_driver(dw_wdt_driver);
 399
 400 MODULE_AUTHOR("Jamie Iles");
 401 MODULE_DESCRIPTION("Synopsys DesignWare Watchdog Driver");
 402 MODULE_LICENSE("GPL");