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