drivers/watchdog/sp805_wdt.c

   1 /*
   2  * drivers/char/watchdog/sp805-wdt.c
   3  *
   4  * Watchdog driver for ARM SP805 watchdog module
   5  *
   6  * Copyright (C) 2010 ST Microelectronics
   7  * Viresh Kumar<viresh.kumar@st.com>
   8  *
   9  * This file is licensed under the terms of the GNU General Public
  10  * License version 2 or later. This program is licensed "as is" without any
  11  * warranty of any kind, whether express or implied.
  12  */
  13
  14 #include <linux/device.h>
  15 #include <linux/resource.h>
  16 #include <linux/amba/bus.h>
  17 #include <linux/bitops.h>
  18 #include <linux/clk.h>
  19 #include <linux/fs.h>
  20 #include <linux/init.h>
  21 #include <linux/io.h>
  22 #include <linux/ioport.h>
  23 #include <linux/kernel.h>
  24 #include <linux/math64.h>
  25 #include <linux/miscdevice.h>
  26 #include <linux/module.h>
  27 #include <linux/moduleparam.h>
  28 #include <linux/slab.h>
  29 #include <linux/spinlock.h>
  30 #include <linux/types.h>
  31 #include <linux/uaccess.h>
  32 #include <linux/watchdog.h>
  33
  34 /* default timeout in seconds */
  35 #define DEFAULT_TIMEOUT         60
  36
  37 #define MODULE_NAME             "sp805-wdt"
  38
  39 /* watchdog register offsets and masks */
  40 #define WDTLOAD                 0x000
  41         #define LOAD_MIN        0x00000001
  42         #define LOAD_MAX        0xFFFFFFFF
  43 #define WDTVALUE                0x004
  44 #define WDTCONTROL              0x008
  45         /* control register masks */
  46         #define INT_ENABLE      (1 << 0)
  47         #define RESET_ENABLE    (1 << 1)
  48 #define WDTINTCLR               0x00C
  49 #define WDTRIS                  0x010
  50 #define WDTMIS                  0x014
  51         #define INT_MASK        (1 << 0)
  52 #define WDTLOCK                 0xC00
  53         #define UNLOCK          0x1ACCE551
  54         #define LOCK            0x00000001
  55
  56 /**
  57  * struct sp805_wdt: sp805 wdt device structure
  58  *
  59  * lock: spin lock protecting dev structure and io access
  60  * base: base address of wdt
  61  * clk: clock structure of wdt
  62  * dev: amba device structure of wdt
  63  * status: current status of wdt
  64  * load_val: load value to be set for current timeout
  65  * timeout: current programmed timeout
  66  */
  67 struct sp805_wdt {
  68         spinlock_t                      lock;
  69         void __iomem                    *base;
  70         struct clk                      *clk;
  71         struct amba_device              *adev;
  72         unsigned long                   status;
  73         #define WDT_BUSY                0
  74         #define WDT_CAN_BE_CLOSED       1
  75         unsigned int                    load_val;
  76         unsigned int                    timeout;
  77 };
  78
  79 /* local variables */
  80 static struct sp805_wdt *wdt;
  81 static int nowayout = WATCHDOG_NOWAYOUT;
  82
  83 /* This routine finds load value that will reset system in required timout */
  84 static void wdt_setload(unsigned int timeout)
  85 {
  86         u64 load, rate;
  87
  88         rate = clk_get_rate(wdt->clk);
  89
  90         /*
  91          * sp805 runs counter with given value twice, after the end of first
  92          * counter it gives an interrupt and then starts counter again. If
  93          * interrupt already occured then it resets the system. This is why
  94          * load is half of what should be required.
  95          */
  96         load = div_u64(rate, 2) * timeout - 1;
  97
  98         load = (load > LOAD_MAX) ? LOAD_MAX : load;
  99         load = (load < LOAD_MIN) ? LOAD_MIN : load;
 100
 101         spin_lock(&wdt->lock);
 102         wdt->load_val = load;
 103         /* roundup timeout to closest positive integer value */
 104         wdt->timeout = div_u64((load + 1) * 2 + (rate / 2), rate);
 105         spin_unlock(&wdt->lock);
 106 }
 107
 108 /* returns number of seconds left for reset to occur */
 109 static u32 wdt_timeleft(void)
 110 {
 111         u64 load, rate;
 112
 113         rate = clk_get_rate(wdt->clk);
 114
 115         spin_lock(&wdt->lock);
 116         load = readl(wdt->base + WDTVALUE);
 117
 118         /*If the interrupt is inactive then time left is WDTValue + WDTLoad. */
 119         if (!(readl(wdt->base + WDTRIS) & INT_MASK))
 120                 load += wdt->load_val + 1;
 121         spin_unlock(&wdt->lock);
 122
 123         return div_u64(load, rate);
 124 }
 125
 126 /* enables watchdog timers reset */
 127 static void wdt_enable(void)
 128 {
 129         spin_lock(&wdt->lock);
 130
 131         writel(UNLOCK, wdt->base + WDTLOCK);
 132         writel(wdt->load_val, wdt->base + WDTLOAD);
 133         writel(INT_MASK, wdt->base + WDTINTCLR);
 134         writel(INT_ENABLE | RESET_ENABLE, wdt->base + WDTCONTROL);
 135         writel(LOCK, wdt->base + WDTLOCK);
 136
 137         spin_unlock(&wdt->lock);
 138 }
 139
 140 /* disables watchdog timers reset */
 141 static void wdt_disable(void)
 142 {
 143         spin_lock(&wdt->lock);
 144
 145         writel(UNLOCK, wdt->base + WDTLOCK);
 146         writel(0, wdt->base + WDTCONTROL);
 147         writel(0, wdt->base + WDTLOAD);
 148         writel(LOCK, wdt->base + WDTLOCK);
 149
 150         spin_unlock(&wdt->lock);
 151 }
 152
 153 static ssize_t sp805_wdt_write(struct file *file, const char *data,
 154                 size_t len, loff_t *ppos)
 155 {
 156         if (len) {
 157                 if (!nowayout) {
 158                         size_t i;
 159
 160                         clear_bit(WDT_CAN_BE_CLOSED, &wdt->status);
 161
 162                         for (i = 0; i != len; i++) {
 163                                 char c;
 164
 165                                 if (get_user(c, data + i))
 166                                         return -EFAULT;
 167                                 /* Check for Magic Close character */
 168                                 if (c == 'V') {
 169                                         set_bit(WDT_CAN_BE_CLOSED,
 170                                                         &wdt->status);
 171                                         break;
 172                                 }
 173                         }
 174                 }
 175                 wdt_enable();
 176         }
 177         return len;
 178 }
 179
 180 static const struct watchdog_info ident = {
 181         .options = WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
 182         .identity = MODULE_NAME,
 183 };
 184
 185 static long sp805_wdt_ioctl(struct file *file, unsigned int cmd,
 186                 unsigned long arg)
 187 {
 188         int ret = -ENOTTY;
 189         unsigned int timeout;
 190
 191         switch (cmd) {
 192         case WDIOC_GETSUPPORT:
 193                 ret = copy_to_user((struct watchdog_info *)arg, &ident,
 194                                 sizeof(ident)) ? -EFAULT : 0;
 195                 break;
 196
 197         case WDIOC_GETSTATUS:
 198                 ret = put_user(0, (int *)arg);
 199                 break;
 200
 201         case WDIOC_KEEPALIVE:
 202                 wdt_enable();
 203                 ret = 0;
 204                 break;
 205
 206         case WDIOC_SETTIMEOUT:
 207                 ret = get_user(timeout, (unsigned int *)arg);
 208                 if (ret)
 209                         break;
 210
 211                 wdt_setload(timeout);
 212
 213                 wdt_enable();
 214                 /* Fall through */
 215
 216         case WDIOC_GETTIMEOUT:
 217                 ret = put_user(wdt->timeout, (unsigned int *)arg);
 218                 break;
 219         case WDIOC_GETTIMELEFT:
 220                 ret = put_user(wdt_timeleft(), (unsigned int *)arg);
 221                 break;
 222         }
 223         return ret;
 224 }
 225
 226 static int sp805_wdt_open(struct inode *inode, struct file *file)
 227 {
 228         int ret = 0;
 229
 230         if (test_and_set_bit(WDT_BUSY, &wdt->status))
 231                 return -EBUSY;
 232
 233         ret = clk_enable(wdt->clk);
 234         if (ret) {
 235                 dev_err(&wdt->adev->dev, "clock enable fail");
 236                 goto err;
 237         }
 238
 239         wdt_enable();
 240
 241         /* can not be closed, once enabled */
 242         clear_bit(WDT_CAN_BE_CLOSED, &wdt->status);
 243         return nonseekable_open(inode, file);
 244
 245 err:
 246         clear_bit(WDT_BUSY, &wdt->status);
 247         return ret;
 248 }
 249
 250 static int sp805_wdt_release(struct inode *inode, struct file *file)
 251 {
 252         if (!test_bit(WDT_CAN_BE_CLOSED, &wdt->status)) {
 253                 clear_bit(WDT_BUSY, &wdt->status);
 254                 dev_warn(&wdt->adev->dev, "Device closed unexpectedly\n");
 255                 return 0;
 256         }
 257
 258         wdt_disable();
 259         clk_disable(wdt->clk);
 260         clear_bit(WDT_BUSY, &wdt->status);
 261
 262         return 0;
 263 }
 264
 265 static const struct file_operations sp805_wdt_fops = {
 266         .owner = THIS_MODULE,
 267         .llseek = no_llseek,
 268         .write = sp805_wdt_write,
 269         .unlocked_ioctl = sp805_wdt_ioctl,
 270         .open = sp805_wdt_open,
 271         .release = sp805_wdt_release,
 272 };
 273
 274 static struct miscdevice sp805_wdt_miscdev = {
 275         .minor = WATCHDOG_MINOR,
 276         .name = "watchdog",
 277         .fops = &sp805_wdt_fops,
 278 };
 279
 280 static int __devinit
 281 sp805_wdt_probe(struct amba_device *adev, const struct amba_id *id)
 282 {
 283         int ret = 0;
 284
 285         if (!request_mem_region(adev->res.start, resource_size(&adev->res),
 286                                 "sp805_wdt")) {
 287                 dev_warn(&adev->dev, "Failed to get memory region resource\n");
 288                 ret = -ENOENT;
 289                 goto err;
 290         }
 291
 292         wdt = kzalloc(sizeof(*wdt), GFP_KERNEL);
 293         if (!wdt) {
 294                 dev_warn(&adev->dev, "Kzalloc failed\n");
 295                 ret = -ENOMEM;
 296                 goto err_kzalloc;
 297         }
 298
 299         wdt->clk = clk_get(&adev->dev, NULL);
 300         if (IS_ERR(wdt->clk)) {
 301                 dev_warn(&adev->dev, "Clock not found\n");
 302                 ret = PTR_ERR(wdt->clk);
 303                 goto err_clk_get;
 304         }
 305
 306         wdt->base = ioremap(adev->res.start, resource_size(&adev->res));
 307         if (!wdt->base) {
 308                 ret = -ENOMEM;
 309                 dev_warn(&adev->dev, "ioremap fail\n");
 310                 goto err_ioremap;
 311         }
 312
 313         wdt->adev = adev;
 314         spin_lock_init(&wdt->lock);
 315         wdt_setload(DEFAULT_TIMEOUT);
 316
 317         ret = misc_register(&sp805_wdt_miscdev);
 318         if (ret < 0) {
 319                 dev_warn(&adev->dev, "cannot register misc device\n");
 320                 goto err_misc_register;
 321         }
 322
 323         dev_info(&adev->dev, "registration successful\n");
 324         return 0;
 325
 326 err_misc_register:
 327         iounmap(wdt->base);
 328 err_ioremap:
 329         clk_put(wdt->clk);
 330 err_clk_get:
 331         kfree(wdt);
 332         wdt = NULL;
 333 err_kzalloc:
 334         release_mem_region(adev->res.start, resource_size(&adev->res));
 335 err:
 336         dev_err(&adev->dev, "Probe Failed!!!\n");
 337         return ret;
 338 }
 339
 340 static int __devexit sp805_wdt_remove(struct amba_device *adev)
 341 {
 342         misc_deregister(&sp805_wdt_miscdev);
 343         iounmap(wdt->base);
 344         clk_put(wdt->clk);
 345         kfree(wdt);
 346         release_mem_region(adev->res.start, resource_size(&adev->res));
 347
 348         return 0;
 349 }
 350
 351 static struct amba_id sp805_wdt_ids[] __initdata = {
 352         {
 353                 .id     = 0x00141805,
 354                 .mask   = 0x00ffffff,
 355         },
 356         { 0, 0 },
 357 };
 358
 359 static struct amba_driver sp805_wdt_driver = {
 360         .drv = {
 361                 .name   = MODULE_NAME,
 362         },
 363         .id_table       = sp805_wdt_ids,
 364         .probe          = sp805_wdt_probe,
 365         .remove = __devexit_p(sp805_wdt_remove),
 366 };
 367
 368 static int __init sp805_wdt_init(void)
 369 {
 370         return amba_driver_register(&sp805_wdt_driver);
 371 }
 372 module_init(sp805_wdt_init);
 373
 374 static void __exit sp805_wdt_exit(void)
 375 {
 376         amba_driver_unregister(&sp805_wdt_driver);
 377 }
 378 module_exit(sp805_wdt_exit);
 379
 380 module_param(nowayout, int, 0);
 381 MODULE_PARM_DESC(nowayout,
 382                 "Set to 1 to keep watchdog running after device release");
 383
 384 MODULE_AUTHOR("Viresh Kumar <viresh.kumar@st.com>");
 385 MODULE_DESCRIPTION("ARM SP805 Watchdog Driver");
 386 MODULE_LICENSE("GPL");
 387 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);