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