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 occurred 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         /* Flush posted writes. */
 138         readl(wdt->base + WDTLOCK);
 139         spin_unlock(&wdt->lock);
 140 }
 141
 142 /* disables watchdog timers reset */
 143 static void wdt_disable(void)
 144 {
 145         spin_lock(&wdt->lock);
 146
 147         writel(UNLOCK, wdt->base + WDTLOCK);
 148         writel(0, wdt->base + WDTCONTROL);
 149         writel(LOCK, wdt->base + WDTLOCK);
 150
 151         /* Flush posted writes. */
 152         readl(wdt->base + WDTLOCK);
 153         spin_unlock(&wdt->lock);
 154 }
 155
 156 static ssize_t sp805_wdt_write(struct file *file, const char *data,
 157                 size_t len, loff_t *ppos)
 158 {
 159         if (len) {
 160                 if (!nowayout) {
 161                         size_t i;
 162
 163                         clear_bit(WDT_CAN_BE_CLOSED, &wdt->status);
 164
 165                         for (i = 0; i != len; i++) {
 166                                 char c;
 167
 168                                 if (get_user(c, data + i))
 169                                         return -EFAULT;
 170                                 /* Check for Magic Close character */
 171                                 if (c == 'V') {
 172                                         set_bit(WDT_CAN_BE_CLOSED,
 173                                                         &wdt->status);
 174                                         break;
 175                                 }
 176                         }
 177                 }
 178                 wdt_enable();
 179         }
 180         return len;
 181 }
 182
 183 static const struct watchdog_info ident = {
 184         .options = WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
 185         .identity = MODULE_NAME,
 186 };
 187
 188 static long sp805_wdt_ioctl(struct file *file, unsigned int cmd,
 189                 unsigned long arg)
 190 {
 191         int ret = -ENOTTY;
 192         unsigned int timeout;
 193
 194         switch (cmd) {
 195         case WDIOC_GETSUPPORT:
 196                 ret = copy_to_user((struct watchdog_info *)arg, &ident,
 197                                 sizeof(ident)) ? -EFAULT : 0;
 198                 break;
 199
 200         case WDIOC_GETSTATUS:
 201                 ret = put_user(0, (int *)arg);
 202                 break;
 203
 204         case WDIOC_KEEPALIVE:
 205                 wdt_enable();
 206                 ret = 0;
 207                 break;
 208
 209         case WDIOC_SETTIMEOUT:
 210                 ret = get_user(timeout, (unsigned int *)arg);
 211                 if (ret)
 212                         break;
 213
 214                 wdt_setload(timeout);
 215
 216                 wdt_enable();
 217                 /* Fall through */
 218
 219         case WDIOC_GETTIMEOUT:
 220                 ret = put_user(wdt->timeout, (unsigned int *)arg);
 221                 break;
 222         case WDIOC_GETTIMELEFT:
 223                 ret = put_user(wdt_timeleft(), (unsigned int *)arg);
 224                 break;
 225         }
 226         return ret;
 227 }
 228
 229 static int sp805_wdt_open(struct inode *inode, struct file *file)
 230 {
 231         int ret = 0;
 232
 233         if (test_and_set_bit(WDT_BUSY, &wdt->status))
 234                 return -EBUSY;
 235
 236         ret = clk_enable(wdt->clk);
 237         if (ret) {
 238                 dev_err(&wdt->adev->dev, "clock enable fail");
 239                 goto err;
 240         }
 241
 242         wdt_enable();
 243
 244         /* can not be closed, once enabled */
 245         clear_bit(WDT_CAN_BE_CLOSED, &wdt->status);
 246         return nonseekable_open(inode, file);
 247
 248 err:
 249         clear_bit(WDT_BUSY, &wdt->status);
 250         return ret;
 251 }
 252
 253 static int sp805_wdt_release(struct inode *inode, struct file *file)
 254 {
 255         if (!test_bit(WDT_CAN_BE_CLOSED, &wdt->status)) {
 256                 clear_bit(WDT_BUSY, &wdt->status);
 257                 dev_warn(&wdt->adev->dev, "Device closed unexpectedly\n");
 258                 return 0;
 259         }
 260
 261         wdt_disable();
 262         clk_disable(wdt->clk);
 263         clear_bit(WDT_BUSY, &wdt->status);
 264
 265         return 0;
 266 }
 267
 268 static const struct file_operations sp805_wdt_fops = {
 269         .owner = THIS_MODULE,
 270         .llseek = no_llseek,
 271         .write = sp805_wdt_write,
 272         .unlocked_ioctl = sp805_wdt_ioctl,
 273         .open = sp805_wdt_open,
 274         .release = sp805_wdt_release,
 275 };
 276
 277 static struct miscdevice sp805_wdt_miscdev = {
 278         .minor = WATCHDOG_MINOR,
 279         .name = "watchdog",
 280         .fops = &sp805_wdt_fops,
 281 };
 282
 283 static int __devinit
 284 sp805_wdt_probe(struct amba_device *adev, const struct amba_id *id)
 285 {
 286         int ret = 0;
 287
 288         if (!request_mem_region(adev->res.start, resource_size(&adev->res),
 289                                 "sp805_wdt")) {
 290                 dev_warn(&adev->dev, "Failed to get memory region resource\n");
 291                 ret = -ENOENT;
 292                 goto err;
 293         }
 294
 295         wdt = kzalloc(sizeof(*wdt), GFP_KERNEL);
 296         if (!wdt) {
 297                 dev_warn(&adev->dev, "Kzalloc failed\n");
 298                 ret = -ENOMEM;
 299                 goto err_kzalloc;
 300         }
 301
 302         wdt->clk = clk_get(&adev->dev, NULL);
 303         if (IS_ERR(wdt->clk)) {
 304                 dev_warn(&adev->dev, "Clock not found\n");
 305                 ret = PTR_ERR(wdt->clk);
 306                 goto err_clk_get;
 307         }
 308
 309         wdt->base = ioremap(adev->res.start, resource_size(&adev->res));
 310         if (!wdt->base) {
 311                 ret = -ENOMEM;
 312                 dev_warn(&adev->dev, "ioremap fail\n");
 313                 goto err_ioremap;
 314         }
 315
 316         wdt->adev = adev;
 317         spin_lock_init(&wdt->lock);
 318         wdt_setload(DEFAULT_TIMEOUT);
 319
 320         ret = misc_register(&sp805_wdt_miscdev);
 321         if (ret < 0) {
 322                 dev_warn(&adev->dev, "cannot register misc device\n");
 323                 goto err_misc_register;
 324         }
 325
 326         dev_info(&adev->dev, "registration successful\n");
 327         return 0;
 328
 329 err_misc_register:
 330         iounmap(wdt->base);
 331 err_ioremap:
 332         clk_put(wdt->clk);
 333 err_clk_get:
 334         kfree(wdt);
 335         wdt = NULL;
 336 err_kzalloc:
 337         release_mem_region(adev->res.start, resource_size(&adev->res));
 338 err:
 339         dev_err(&adev->dev, "Probe Failed!!!\n");
 340         return ret;
 341 }
 342
 343 static int __devexit sp805_wdt_remove(struct amba_device *adev)
 344 {
 345         misc_deregister(&sp805_wdt_miscdev);
 346         iounmap(wdt->base);
 347         clk_put(wdt->clk);
 348         kfree(wdt);
 349         release_mem_region(adev->res.start, resource_size(&adev->res));
 350
 351         return 0;
 352 }
 353
 354 static struct amba_id sp805_wdt_ids[] __initdata = {
 355         {
 356                 .id     = 0x00141805,
 357                 .mask   = 0x00ffffff,
 358         },
 359         { 0, 0 },
 360 };
 361
 362 static struct amba_driver sp805_wdt_driver = {
 363         .drv = {
 364                 .name   = MODULE_NAME,
 365         },
 366         .id_table       = sp805_wdt_ids,
 367         .probe          = sp805_wdt_probe,
 368         .remove = __devexit_p(sp805_wdt_remove),
 369 };
 370
 371 static int __init sp805_wdt_init(void)
 372 {
 373         return amba_driver_register(&sp805_wdt_driver);
 374 }
 375 module_init(sp805_wdt_init);
 376
 377 static void __exit sp805_wdt_exit(void)
 378 {
 379         amba_driver_unregister(&sp805_wdt_driver);
 380 }
 381 module_exit(sp805_wdt_exit);
 382
 383 module_param(nowayout, int, 0);
 384 MODULE_PARM_DESC(nowayout,
 385                 "Set to 1 to keep watchdog running after device release");
 386
 387 MODULE_AUTHOR("Viresh Kumar <viresh.kumar@st.com>");
 388 MODULE_DESCRIPTION("ARM SP805 Watchdog Driver");
 389 MODULE_LICENSE("GPL");
 390 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);