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");