drivers/watchdog/shwdt.c

   1 /*
   2  * drivers/watchdog/shwdt.c
   3  *
   4  * Watchdog driver for integrated watchdog in the SuperH processors.
   5  *
   6  * Copyright (C) 2001 - 2012  Paul Mundt <lethal@linux-sh.org>
   7  *
   8  * This program is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU General Public License as published by the
  10  * Free Software Foundation; either version 2 of the License, or (at your
  11  * option) any later version.
  12  *
  13  * 14-Dec-2001 Matt Domsch <Matt_Domsch@dell.com>
  14  *     Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT
  15  *
  16  * 19-Apr-2002 Rob Radez <rob@osinvestor.com>
  17  *     Added expect close support, made emulated timeout runtime changeable
  18  *     general cleanups, add some ioctls
  19  */
  20
  21 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  22
  23 #include <linux/module.h>
  24 #include <linux/moduleparam.h>
  25 #include <linux/platform_device.h>
  26 #include <linux/init.h>
  27 #include <linux/types.h>
  28 #include <linux/spinlock.h>
  29 #include <linux/miscdevice.h>
  30 #include <linux/watchdog.h>
  31 #include <linux/pm_runtime.h>
  32 #include <linux/fs.h>
  33 #include <linux/mm.h>
  34 #include <linux/slab.h>
  35 #include <linux/io.h>
  36 #include <linux/clk.h>
  37 #include <linux/err.h>
  38 #include <asm/watchdog.h>
  39
  40 #define DRV_NAME "sh-wdt"
  41
  42 /*
  43  * Default clock division ratio is 5.25 msecs. For an additional table of
  44  * values, consult the asm-sh/watchdog.h. Overload this at module load
  45  * time.
  46  *
  47  * In order for this to work reliably we need to have HZ set to 1000 or
  48  * something quite higher than 100 (or we need a proper high-res timer
  49  * implementation that will deal with this properly), otherwise the 10ms
  50  * resolution of a jiffy is enough to trigger the overflow. For things like
  51  * the SH-4 and SH-5, this isn't necessarily that big of a problem, though
  52  * for the SH-2 and SH-3, this isn't recommended unless the WDT is absolutely
  53  * necssary.
  54  *
  55  * As a result of this timing problem, the only modes that are particularly
  56  * feasible are the 4096 and the 2048 divisors, which yield 5.25 and 2.62ms
  57  * overflow periods respectively.
  58  *
  59  * Also, since we can't really expect userspace to be responsive enough
  60  * before the overflow happens, we maintain two separate timers .. One in
  61  * the kernel for clearing out WOVF every 2ms or so (again, this depends on
  62  * HZ == 1000), and another for monitoring userspace writes to the WDT device.
  63  *
  64  * As such, we currently use a configurable heartbeat interval which defaults
  65  * to 30s. In this case, the userspace daemon is only responsible for periodic
  66  * writes to the device before the next heartbeat is scheduled. If the daemon
  67  * misses its deadline, the kernel timer will allow the WDT to overflow.
  68  */
  69 static int clock_division_ratio = WTCSR_CKS_4096;
  70 #define next_ping_period(cks)   (jiffies + msecs_to_jiffies(cks - 4))
  71
  72 #define WATCHDOG_HEARTBEAT 30                   /* 30 sec default heartbeat */
  73 static int heartbeat = WATCHDOG_HEARTBEAT;      /* in seconds */
  74 static bool nowayout = WATCHDOG_NOWAYOUT;
  75 static unsigned long next_heartbeat;
  76
  77 struct sh_wdt {
  78         void __iomem            *base;
  79         struct device           *dev;
  80         struct clk              *clk;
  81         spinlock_t              lock;
  82
  83         struct timer_list       timer;
  84 };
  85
  86 static int sh_wdt_start(struct watchdog_device *wdt_dev)
  87 {
  88         struct sh_wdt *wdt = watchdog_get_drvdata(wdt_dev);
  89         unsigned long flags;
  90         u8 csr;
  91
  92         pm_runtime_get_sync(wdt->dev);
  93         clk_enable(wdt->clk);
  94
  95         spin_lock_irqsave(&wdt->lock, flags);
  96
  97         next_heartbeat = jiffies + (heartbeat * HZ);
  98         mod_timer(&wdt->timer, next_ping_period(clock_division_ratio));
  99
 100         csr = sh_wdt_read_csr();
 101         csr |= WTCSR_WT | clock_division_ratio;
 102         sh_wdt_write_csr(csr);
 103
 104         sh_wdt_write_cnt(0);
 105
 106         /*
 107          * These processors have a bit of an inconsistent initialization
 108          * process.. starting with SH-3, RSTS was moved to WTCSR, and the
 109          * RSTCSR register was removed.
 110          *
 111          * On the SH-2 however, in addition with bits being in different
 112          * locations, we must deal with RSTCSR outright..
 113          */
 114         csr = sh_wdt_read_csr();
 115         csr |= WTCSR_TME;
 116         csr &= ~WTCSR_RSTS;
 117         sh_wdt_write_csr(csr);
 118
 119 #ifdef CONFIG_CPU_SH2
 120         csr = sh_wdt_read_rstcsr();
 121         csr &= ~RSTCSR_RSTS;
 122         sh_wdt_write_rstcsr(csr);
 123 #endif
 124         spin_unlock_irqrestore(&wdt->lock, flags);
 125
 126         return 0;
 127 }
 128
 129 static int sh_wdt_stop(struct watchdog_device *wdt_dev)
 130 {
 131         struct sh_wdt *wdt = watchdog_get_drvdata(wdt_dev);
 132         unsigned long flags;
 133         u8 csr;
 134
 135         spin_lock_irqsave(&wdt->lock, flags);
 136
 137         del_timer(&wdt->timer);
 138
 139         csr = sh_wdt_read_csr();
 140         csr &= ~WTCSR_TME;
 141         sh_wdt_write_csr(csr);
 142
 143         spin_unlock_irqrestore(&wdt->lock, flags);
 144
 145         clk_disable(wdt->clk);
 146         pm_runtime_put_sync(wdt->dev);
 147
 148         return 0;
 149 }
 150
 151 static int sh_wdt_keepalive(struct watchdog_device *wdt_dev)
 152 {
 153         struct sh_wdt *wdt = watchdog_get_drvdata(wdt_dev);
 154         unsigned long flags;
 155
 156         spin_lock_irqsave(&wdt->lock, flags);
 157         next_heartbeat = jiffies + (heartbeat * HZ);
 158         spin_unlock_irqrestore(&wdt->lock, flags);
 159
 160         return 0;
 161 }
 162
 163 static int sh_wdt_set_heartbeat(struct watchdog_device *wdt_dev, unsigned t)
 164 {
 165         struct sh_wdt *wdt = watchdog_get_drvdata(wdt_dev);
 166         unsigned long flags;
 167
 168         if (unlikely(t < 1 || t > 3600)) /* arbitrary upper limit */
 169                 return -EINVAL;
 170
 171         spin_lock_irqsave(&wdt->lock, flags);
 172         heartbeat = t;
 173         wdt_dev->timeout = t;
 174         spin_unlock_irqrestore(&wdt->lock, flags);
 175
 176         return 0;
 177 }
 178
 179 static void sh_wdt_ping(unsigned long data)
 180 {
 181         struct sh_wdt *wdt = (struct sh_wdt *)data;
 182         unsigned long flags;
 183
 184         spin_lock_irqsave(&wdt->lock, flags);
 185         if (time_before(jiffies, next_heartbeat)) {
 186                 u8 csr;
 187
 188                 csr = sh_wdt_read_csr();
 189                 csr &= ~WTCSR_IOVF;
 190                 sh_wdt_write_csr(csr);
 191
 192                 sh_wdt_write_cnt(0);
 193
 194                 mod_timer(&wdt->timer, next_ping_period(clock_division_ratio));
 195         } else
 196                 dev_warn(wdt->dev, "Heartbeat lost! Will not ping "
 197                          "the watchdog\n");
 198         spin_unlock_irqrestore(&wdt->lock, flags);
 199 }
 200
 201 static const struct watchdog_info sh_wdt_info = {
 202         .options                = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
 203                                   WDIOF_MAGICCLOSE,
 204         .firmware_version       = 1,
 205         .identity               = "SH WDT",
 206 };
 207
 208 static const struct watchdog_ops sh_wdt_ops = {
 209         .owner          = THIS_MODULE,
 210         .start          = sh_wdt_start,
 211         .stop           = sh_wdt_stop,
 212         .ping           = sh_wdt_keepalive,
 213         .set_timeout    = sh_wdt_set_heartbeat,
 214 };
 215
 216 static struct watchdog_device sh_wdt_dev = {
 217         .info   = &sh_wdt_info,
 218         .ops    = &sh_wdt_ops,
 219 };
 220
 221 static int sh_wdt_probe(struct platform_device *pdev)
 222 {
 223         struct sh_wdt *wdt;
 224         struct resource *res;
 225         int rc;
 226
 227         /*
 228          * As this driver only covers the global watchdog case, reject
 229          * any attempts to register per-CPU watchdogs.
 230          */
 231         if (pdev->id != -1)
 232                 return -EINVAL;
 233
 234         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 235         if (unlikely(!res))
 236                 return -EINVAL;
 237
 238         wdt = devm_kzalloc(&pdev->dev, sizeof(struct sh_wdt), GFP_KERNEL);
 239         if (unlikely(!wdt))
 240                 return -ENOMEM;
 241
 242         wdt->dev = &pdev->dev;
 243
 244         wdt->clk = devm_clk_get(&pdev->dev, NULL);
 245         if (IS_ERR(wdt->clk)) {
 246                 /*
 247                  * Clock framework support is optional, continue on
 248                  * anyways if we don't find a matching clock.
 249                  */
 250                 wdt->clk = NULL;
 251         }
 252
 253         wdt->base = devm_ioremap_resource(wdt->dev, res);
 254         if (IS_ERR(wdt->base))
 255                 return PTR_ERR(wdt->base);
 256
 257         watchdog_set_nowayout(&sh_wdt_dev, nowayout);
 258         watchdog_set_drvdata(&sh_wdt_dev, wdt);
 259
 260         spin_lock_init(&wdt->lock);
 261
 262         rc = sh_wdt_set_heartbeat(&sh_wdt_dev, heartbeat);
 263         if (unlikely(rc)) {
 264                 /* Default timeout if invalid */
 265                 sh_wdt_set_heartbeat(&sh_wdt_dev, WATCHDOG_HEARTBEAT);
 266
 267                 dev_warn(&pdev->dev,
 268                          "heartbeat value must be 1<=x<=3600, using %d\n",
 269                          sh_wdt_dev.timeout);
 270         }
 271
 272         dev_info(&pdev->dev, "configured with heartbeat=%d sec (nowayout=%d)\n",
 273                  sh_wdt_dev.timeout, nowayout);
 274
 275         rc = watchdog_register_device(&sh_wdt_dev);
 276         if (unlikely(rc)) {
 277                 dev_err(&pdev->dev, "Can't register watchdog (err=%d)\n", rc);
 278                 return rc;
 279         }
 280
 281         init_timer(&wdt->timer);
 282         wdt->timer.function     = sh_wdt_ping;
 283         wdt->timer.data         = (unsigned long)wdt;
 284         wdt->timer.expires      = next_ping_period(clock_division_ratio);
 285
 286         platform_set_drvdata(pdev, wdt);
 287
 288         dev_info(&pdev->dev, "initialized.\n");
 289
 290         pm_runtime_enable(&pdev->dev);
 291
 292         return 0;
 293 }
 294
 295 static int sh_wdt_remove(struct platform_device *pdev)
 296 {
 297         struct sh_wdt *wdt = platform_get_drvdata(pdev);
 298
 299         watchdog_unregister_device(&sh_wdt_dev);
 300
 301         pm_runtime_disable(&pdev->dev);
 302
 303         return 0;
 304 }
 305
 306 static void sh_wdt_shutdown(struct platform_device *pdev)
 307 {
 308         sh_wdt_stop(&sh_wdt_dev);
 309 }
 310
 311 static struct platform_driver sh_wdt_driver = {
 312         .driver         = {
 313                 .name   = DRV_NAME,
 314                 .owner  = THIS_MODULE,
 315         },
 316
 317         .probe          = sh_wdt_probe,
 318         .remove         = sh_wdt_remove,
 319         .shutdown       = sh_wdt_shutdown,
 320 };
 321
 322 static int __init sh_wdt_init(void)
 323 {
 324         if (unlikely(clock_division_ratio < 0x5 ||
 325                      clock_division_ratio > 0x7)) {
 326                 clock_division_ratio = WTCSR_CKS_4096;
 327
 328                 pr_info("divisor must be 0x5<=x<=0x7, using %d\n",
 329                         clock_division_ratio);
 330         }
 331
 332         return platform_driver_register(&sh_wdt_driver);
 333 }
 334
 335 static void __exit sh_wdt_exit(void)
 336 {
 337         platform_driver_unregister(&sh_wdt_driver);
 338 }
 339 module_init(sh_wdt_init);
 340 module_exit(sh_wdt_exit);
 341
 342 MODULE_AUTHOR("Paul Mundt <lethal@linux-sh.org>");
 343 MODULE_DESCRIPTION("SuperH watchdog driver");
 344 MODULE_LICENSE("GPL");
 345 MODULE_ALIAS("platform:" DRV_NAME);
 346 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
 347
 348 module_param(clock_division_ratio, int, 0);
 349 MODULE_PARM_DESC(clock_division_ratio,
 350         "Clock division ratio. Valid ranges are from 0x5 (1.31ms) "
 351         "to 0x7 (5.25ms). (default=" __MODULE_STRING(WTCSR_CKS_4096) ")");
 352
 353 module_param(heartbeat, int, 0);
 354 MODULE_PARM_DESC(heartbeat,
 355         "Watchdog heartbeat in seconds. (1 <= heartbeat <= 3600, default="
 356                                 __MODULE_STRING(WATCHDOG_HEARTBEAT) ")");
 357
 358 module_param(nowayout, bool, 0);
 359 MODULE_PARM_DESC(nowayout,
 360         "Watchdog cannot be stopped once started (default="
 361                                 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");