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_TIMEOUT_RANGE_TOPINIT_SHIFT    4
  44 #define WDOG_CURRENT_COUNT_REG_OFFSET       0x08
  45 #define WDOG_COUNTER_RESTART_REG_OFFSET     0x0c
  46 #define WDOG_COUNTER_RESTART_KICK_VALUE     0x76
  47
  48 /* The maximum TOP (timeout period) value that can be set in the watchdog. */
  49 #define DW_WDT_MAX_TOP          15
  50
  51 static bool nowayout = WATCHDOG_NOWAYOUT;
  52 module_param(nowayout, bool, 0);
  53 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
  54                  "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  55
  56 #define WDT_TIMEOUT             (HZ / 2)
  57
  58 static struct {
  59         spinlock_t              lock;
  60         void __iomem            *regs;
  61         struct clk              *clk;
  62         unsigned long           in_use;
  63         unsigned long           next_heartbeat;
  64         struct timer_list       timer;
  65         int                     expect_close;
  66 } dw_wdt;
  67
  68 static inline int dw_wdt_is_enabled(void)
  69 {
  70         return readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET) &
  71                 WDOG_CONTROL_REG_WDT_EN_MASK;
  72 }
  73
  74 static inline int dw_wdt_top_in_seconds(unsigned top)
  75 {
  76         /*
  77          * There are 16 possible timeout values in 0..15 where the number of
  78          * cycles is 2 ^ (16 + i) and the watchdog counts down.
  79          */
  80         return (1 << (16 + top)) / clk_get_rate(dw_wdt.clk);
  81 }
  82
  83 static int dw_wdt_get_top(void)
  84 {
  85         int top = readl(dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET) & 0xF;
  86
  87         return dw_wdt_top_in_seconds(top);
  88 }
  89
  90 static inline void dw_wdt_set_next_heartbeat(void)
  91 {
  92         dw_wdt.next_heartbeat = jiffies + dw_wdt_get_top() * HZ;
  93 }
  94
  95 static int dw_wdt_set_top(unsigned top_s)
  96 {
  97         int i, top_val = DW_WDT_MAX_TOP;
  98
  99         /*
 100          * Iterate over the timeout values until we find the closest match. We
 101          * always look for >=.
 102          */
 103         for (i = 0; i <= DW_WDT_MAX_TOP; ++i)
 104                 if (dw_wdt_top_in_seconds(i) >= top_s) {
 105                         top_val = i;
 106                         break;
 107                 }
 108
 109         /* Set the new value in the watchdog. */
 110         writel(top_val | top_val << WDOG_TIMEOUT_RANGE_TOPINIT_SHIFT,
 111                 dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);
 112
 113         dw_wdt_set_next_heartbeat();
 114
 115         return dw_wdt_top_in_seconds(top_val);
 116 }
 117
 118 static void dw_wdt_keepalive(void)
 119 {
 120         writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
 121                WDOG_COUNTER_RESTART_REG_OFFSET);
 122 }
 123
 124 static void dw_wdt_ping(unsigned long data)
 125 {
 126         if (time_before(jiffies, dw_wdt.next_heartbeat) ||
 127             (!nowayout && !dw_wdt.in_use)) {
 128                 dw_wdt_keepalive();
 129                 mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
 130         } else
 131                 pr_crit("keepalive missed, machine will reset\n");
 132 }
 133
 134 static int dw_wdt_open(struct inode *inode, struct file *filp)
 135 {
 136         if (test_and_set_bit(0, &dw_wdt.in_use))
 137                 return -EBUSY;
 138
 139         /* Make sure we don't get unloaded. */
 140         __module_get(THIS_MODULE);
 141
 142         spin_lock(&dw_wdt.lock);
 143         if (!dw_wdt_is_enabled()) {
 144                 /*
 145                  * The watchdog is not currently enabled. Set the timeout to
 146                  * the maximum and then start it.
 147                  */
 148                 dw_wdt_set_top(DW_WDT_MAX_TOP);
 149                 writel(WDOG_CONTROL_REG_WDT_EN_MASK,
 150                        dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
 151         }
 152
 153         dw_wdt_set_next_heartbeat();
 154
 155         spin_unlock(&dw_wdt.lock);
 156
 157         return nonseekable_open(inode, filp);
 158 }
 159
 160 static ssize_t dw_wdt_write(struct file *filp, const char __user *buf,
 161                             size_t len, loff_t *offset)
 162 {
 163         if (!len)
 164                 return 0;
 165
 166         if (!nowayout) {
 167                 size_t i;
 168
 169                 dw_wdt.expect_close = 0;
 170
 171                 for (i = 0; i < len; ++i) {
 172                         char c;
 173
 174                         if (get_user(c, buf + i))
 175                                 return -EFAULT;
 176
 177                         if (c == 'V') {
 178                                 dw_wdt.expect_close = 1;
 179                                 break;
 180                         }
 181                 }
 182         }
 183
 184         dw_wdt_set_next_heartbeat();
 185         mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
 186
 187         return len;
 188 }
 189
 190 static u32 dw_wdt_time_left(void)
 191 {
 192         return readl(dw_wdt.regs + WDOG_CURRENT_COUNT_REG_OFFSET) /
 193                 clk_get_rate(dw_wdt.clk);
 194 }
 195
 196 static const struct watchdog_info dw_wdt_ident = {
 197         .options        = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
 198                           WDIOF_MAGICCLOSE,
 199         .identity       = "Synopsys DesignWare Watchdog",
 200 };
 201
 202 static long dw_wdt_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 203 {
 204         unsigned long val;
 205         int timeout;
 206
 207         switch (cmd) {
 208         case WDIOC_GETSUPPORT:
 209                 return copy_to_user((void __user *)arg, &dw_wdt_ident,
 210                                     sizeof(dw_wdt_ident)) ? -EFAULT : 0;
 211
 212         case WDIOC_GETSTATUS:
 213         case WDIOC_GETBOOTSTATUS:
 214                 return put_user(0, (int __user *)arg);
 215
 216         case WDIOC_KEEPALIVE:
 217                 dw_wdt_set_next_heartbeat();
 218                 return 0;
 219
 220         case WDIOC_SETTIMEOUT:
 221                 if (get_user(val, (int __user *)arg))
 222                         return -EFAULT;
 223                 timeout = dw_wdt_set_top(val);
 224                 return put_user(timeout , (int __user *)arg);
 225
 226         case WDIOC_GETTIMEOUT:
 227                 return put_user(dw_wdt_get_top(), (int __user *)arg);
 228
 229         case WDIOC_GETTIMELEFT:
 230                 /* Get the time left until expiry. */
 231                 if (get_user(val, (int __user *)arg))
 232                         return -EFAULT;
 233                 return put_user(dw_wdt_time_left(), (int __user *)arg);
 234
 235         default:
 236                 return -ENOTTY;
 237         }
 238 }
 239
 240 static int dw_wdt_release(struct inode *inode, struct file *filp)
 241 {
 242         clear_bit(0, &dw_wdt.in_use);
 243
 244         if (!dw_wdt.expect_close) {
 245                 del_timer(&dw_wdt.timer);
 246
 247                 if (!nowayout)
 248                         pr_crit("unexpected close, system will reboot soon\n");
 249                 else
 250                         pr_crit("watchdog cannot be disabled, system will reboot soon\n");
 251         }
 252
 253         dw_wdt.expect_close = 0;
 254
 255         return 0;
 256 }
 257
 258 #ifdef CONFIG_PM_SLEEP
 259 static int dw_wdt_suspend(struct device *dev)
 260 {
 261         clk_disable_unprepare(dw_wdt.clk);
 262
 263         return 0;
 264 }
 265
 266 static int dw_wdt_resume(struct device *dev)
 267 {
 268         int err = clk_prepare_enable(dw_wdt.clk);
 269
 270         if (err)
 271                 return err;
 272
 273         dw_wdt_keepalive();
 274
 275         return 0;
 276 }
 277 #endif /* CONFIG_PM_SLEEP */
 278
 279 static SIMPLE_DEV_PM_OPS(dw_wdt_pm_ops, dw_wdt_suspend, dw_wdt_resume);
 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         dw_wdt.regs = devm_ioremap_resource(&pdev->dev, mem);
 302         if (IS_ERR(dw_wdt.regs))
 303                 return PTR_ERR(dw_wdt.regs);
 304
 305         dw_wdt.clk = devm_clk_get(&pdev->dev, NULL);
 306         if (IS_ERR(dw_wdt.clk))
 307                 return PTR_ERR(dw_wdt.clk);
 308
 309         ret = clk_prepare_enable(dw_wdt.clk);
 310         if (ret)
 311                 return ret;
 312
 313         spin_lock_init(&dw_wdt.lock);
 314
 315         ret = misc_register(&dw_wdt_miscdev);
 316         if (ret)
 317                 goto out_disable_clk;
 318
 319         dw_wdt_set_next_heartbeat();
 320         setup_timer(&dw_wdt.timer, dw_wdt_ping, 0);
 321         mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
 322
 323         return 0;
 324
 325 out_disable_clk:
 326         clk_disable_unprepare(dw_wdt.clk);
 327
 328         return ret;
 329 }
 330
 331 static int dw_wdt_drv_remove(struct platform_device *pdev)
 332 {
 333         misc_deregister(&dw_wdt_miscdev);
 334
 335         clk_disable_unprepare(dw_wdt.clk);
 336
 337         return 0;
 338 }
 339
 340 #ifdef CONFIG_OF
 341 static const struct of_device_id dw_wdt_of_match[] = {
 342         { .compatible = "snps,dw-wdt", },
 343         { /* sentinel */ }
 344 };
 345 MODULE_DEVICE_TABLE(of, dw_wdt_of_match);
 346 #endif
 347
 348 static struct platform_driver dw_wdt_driver = {
 349         .probe          = dw_wdt_drv_probe,
 350         .remove         = dw_wdt_drv_remove,
 351         .driver         = {
 352                 .name   = "dw_wdt",
 353                 .owner  = THIS_MODULE,
 354                 .of_match_table = of_match_ptr(dw_wdt_of_match),
 355                 .pm     = &dw_wdt_pm_ops,
 356         },
 357 };
 358
 359 module_platform_driver(dw_wdt_driver);
 360
 361 MODULE_AUTHOR("Jamie Iles");
 362 MODULE_DESCRIPTION("Synopsys DesignWare Watchdog Driver");
 363 MODULE_LICENSE("GPL");