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