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