drivers/watchdog/at32ap700x_wdt.c

   1 /*
   2  * Watchdog driver for Atmel AT32AP700X devices
   3  *
   4  * Copyright (C) 2005-2006 Atmel Corporation
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  *
  11  * Errata: WDT Clear is blocked after WDT Reset
  12  *
  13  * A watchdog timer event will, after reset, block writes to the WDT_CLEAR
  14  * register, preventing the program to clear the next Watchdog Timer Reset.
  15  *
  16  * If you still want to use the WDT after a WDT reset a small code can be
  17  * insterted at the startup checking the AVR32_PM.rcause register for WDT reset
  18  * and use a GPIO pin to reset the system. This method requires that one of the
  19  * GPIO pins are available and connected externally to the RESET_N pin. After
  20  * the GPIO pin has pulled down the reset line the GPIO will be reset and leave
  21  * the pin tristated with pullup.
  22  */
  23
  24 #include <linux/init.h>
  25 #include <linux/kernel.h>
  26 #include <linux/module.h>
  27 #include <linux/moduleparam.h>
  28 #include <linux/miscdevice.h>
  29 #include <linux/fs.h>
  30 #include <linux/platform_device.h>
  31 #include <linux/watchdog.h>
  32 #include <linux/uaccess.h>
  33 #include <linux/io.h>
  34 #include <linux/spinlock.h>
  35 #include <linux/slab.h>
  36
  37 #define TIMEOUT_MIN             1
  38 #define TIMEOUT_MAX             2
  39 #define TIMEOUT_DEFAULT         TIMEOUT_MAX
  40
  41 /* module parameters */
  42 static int timeout =  TIMEOUT_DEFAULT;
  43 module_param(timeout, int, 0);
  44 MODULE_PARM_DESC(timeout,
  45                 "Timeout value. Limited to be 1 or 2 seconds. (default="
  46                 __MODULE_STRING(TIMEOUT_DEFAULT) ")");
  47
  48 static bool nowayout = WATCHDOG_NOWAYOUT;
  49 module_param(nowayout, bool, 0);
  50 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
  51                 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  52
  53 /* Watchdog registers and write/read macro */
  54 #define WDT_CTRL                0x00
  55 #define WDT_CTRL_EN                0
  56 #define WDT_CTRL_PSEL              8
  57 #define WDT_CTRL_KEY              24
  58
  59 #define WDT_CLR                 0x04
  60
  61 #define WDT_RCAUSE              0x10
  62 #define WDT_RCAUSE_POR             0
  63 #define WDT_RCAUSE_EXT             2
  64 #define WDT_RCAUSE_WDT             3
  65 #define WDT_RCAUSE_JTAG            4
  66 #define WDT_RCAUSE_SERP            5
  67
  68 #define WDT_BIT(name)           (1 << WDT_##name)
  69 #define WDT_BF(name, value)     ((value) << WDT_##name)
  70
  71 #define wdt_readl(dev, reg)                             \
  72         __raw_readl((dev)->regs + WDT_##reg)
  73 #define wdt_writel(dev, reg, value)                     \
  74         __raw_writel((value), (dev)->regs + WDT_##reg)
  75
  76 struct wdt_at32ap700x {
  77         void __iomem            *regs;
  78         spinlock_t              io_lock;
  79         int                     timeout;
  80         int                     boot_status;
  81         unsigned long           users;
  82         struct miscdevice       miscdev;
  83 };
  84
  85 static struct wdt_at32ap700x *wdt;
  86 static char expect_release;
  87
  88 /*
  89  * Disable the watchdog.
  90  */
  91 static inline void at32_wdt_stop(void)
  92 {
  93         unsigned long psel;
  94
  95         spin_lock(&wdt->io_lock);
  96         psel = wdt_readl(wdt, CTRL) & WDT_BF(CTRL_PSEL, 0x0f);
  97         wdt_writel(wdt, CTRL, psel | WDT_BF(CTRL_KEY, 0x55));
  98         wdt_writel(wdt, CTRL, psel | WDT_BF(CTRL_KEY, 0xaa));
  99         spin_unlock(&wdt->io_lock);
 100 }
 101
 102 /*
 103  * Enable and reset the watchdog.
 104  */
 105 static inline void at32_wdt_start(void)
 106 {
 107         /* 0xf is 2^16 divider = 2 sec, 0xe is 2^15 divider = 1 sec */
 108         unsigned long psel = (wdt->timeout > 1) ? 0xf : 0xe;
 109
 110         spin_lock(&wdt->io_lock);
 111         wdt_writel(wdt, CTRL, WDT_BIT(CTRL_EN)
 112                         | WDT_BF(CTRL_PSEL, psel)
 113                         | WDT_BF(CTRL_KEY, 0x55));
 114         wdt_writel(wdt, CTRL, WDT_BIT(CTRL_EN)
 115                         | WDT_BF(CTRL_PSEL, psel)
 116                         | WDT_BF(CTRL_KEY, 0xaa));
 117         spin_unlock(&wdt->io_lock);
 118 }
 119
 120 /*
 121  * Pat the watchdog timer.
 122  */
 123 static inline void at32_wdt_pat(void)
 124 {
 125         spin_lock(&wdt->io_lock);
 126         wdt_writel(wdt, CLR, 0x42);
 127         spin_unlock(&wdt->io_lock);
 128 }
 129
 130 /*
 131  * Watchdog device is opened, and watchdog starts running.
 132  */
 133 static int at32_wdt_open(struct inode *inode, struct file *file)
 134 {
 135         if (test_and_set_bit(1, &wdt->users))
 136                 return -EBUSY;
 137
 138         at32_wdt_start();
 139         return nonseekable_open(inode, file);
 140 }
 141
 142 /*
 143  * Close the watchdog device.
 144  */
 145 static int at32_wdt_close(struct inode *inode, struct file *file)
 146 {
 147         if (expect_release == 42) {
 148                 at32_wdt_stop();
 149         } else {
 150                 dev_dbg(wdt->miscdev.parent,
 151                         "unexpected close, not stopping watchdog!\n");
 152                 at32_wdt_pat();
 153         }
 154         clear_bit(1, &wdt->users);
 155         expect_release = 0;
 156         return 0;
 157 }
 158
 159 /*
 160  * Change the watchdog time interval.
 161  */
 162 static int at32_wdt_settimeout(int time)
 163 {
 164         /*
 165          * All counting occurs at 1 / SLOW_CLOCK (32 kHz) and max prescaler is
 166          * 2 ^ 16 allowing up to 2 seconds timeout.
 167          */
 168         if ((time < TIMEOUT_MIN) || (time > TIMEOUT_MAX))
 169                 return -EINVAL;
 170
 171         /*
 172          * Set new watchdog time. It will be used when at32_wdt_start() is
 173          * called.
 174          */
 175         wdt->timeout = time;
 176         return 0;
 177 }
 178
 179 /*
 180  * Get the watchdog status.
 181  */
 182 static int at32_wdt_get_status(void)
 183 {
 184         int rcause;
 185         int status = 0;
 186
 187         rcause = wdt_readl(wdt, RCAUSE);
 188
 189         switch (rcause) {
 190         case WDT_BIT(RCAUSE_EXT):
 191                 status = WDIOF_EXTERN1;
 192                 break;
 193         case WDT_BIT(RCAUSE_WDT):
 194                 status = WDIOF_CARDRESET;
 195                 break;
 196         case WDT_BIT(RCAUSE_POR):  /* fall through */
 197         case WDT_BIT(RCAUSE_JTAG): /* fall through */
 198         case WDT_BIT(RCAUSE_SERP): /* fall through */
 199         default:
 200                 break;
 201         }
 202
 203         return status;
 204 }
 205
 206 static const struct watchdog_info at32_wdt_info = {
 207         .identity       = "at32ap700x watchdog",
 208         .options        = WDIOF_SETTIMEOUT |
 209                           WDIOF_KEEPALIVEPING |
 210                           WDIOF_MAGICCLOSE,
 211 };
 212
 213 /*
 214  * Handle commands from user-space.
 215  */
 216 static long at32_wdt_ioctl(struct file *file,
 217                                 unsigned int cmd, unsigned long arg)
 218 {
 219         int ret = -ENOTTY;
 220         int time;
 221         void __user *argp = (void __user *)arg;
 222         int __user *p = argp;
 223
 224         switch (cmd) {
 225         case WDIOC_GETSUPPORT:
 226                 ret = copy_to_user(argp, &at32_wdt_info,
 227                                 sizeof(at32_wdt_info)) ? -EFAULT : 0;
 228                 break;
 229         case WDIOC_GETSTATUS:
 230                 ret = put_user(0, p);
 231                 break;
 232         case WDIOC_GETBOOTSTATUS:
 233                 ret = put_user(wdt->boot_status, p);
 234                 break;
 235         case WDIOC_SETOPTIONS:
 236                 ret = get_user(time, p);
 237                 if (ret)
 238                         break;
 239                 if (time & WDIOS_DISABLECARD)
 240                         at32_wdt_stop();
 241                 if (time & WDIOS_ENABLECARD)
 242                         at32_wdt_start();
 243                 ret = 0;
 244                 break;
 245         case WDIOC_KEEPALIVE:
 246                 at32_wdt_pat();
 247                 ret = 0;
 248                 break;
 249         case WDIOC_SETTIMEOUT:
 250                 ret = get_user(time, p);
 251                 if (ret)
 252                         break;
 253                 ret = at32_wdt_settimeout(time);
 254                 if (ret)
 255                         break;
 256                 /* Enable new time value */
 257                 at32_wdt_start();
 258                 /* fall through */
 259         case WDIOC_GETTIMEOUT:
 260                 ret = put_user(wdt->timeout, p);
 261                 break;
 262         }
 263
 264         return ret;
 265 }
 266
 267 static ssize_t at32_wdt_write(struct file *file, const char __user *data,
 268                                 size_t len, loff_t *ppos)
 269 {
 270         /* See if we got the magic character 'V' and reload the timer */
 271         if (len) {
 272                 if (!nowayout) {
 273                         size_t i;
 274
 275                         /*
 276                          * note: just in case someone wrote the magic
 277                          * character five months ago...
 278                          */
 279                         expect_release = 0;
 280
 281                         /*
 282                          * scan to see whether or not we got the magic
 283                          * character
 284                          */
 285                         for (i = 0; i != len; i++) {
 286                                 char c;
 287                                 if (get_user(c, data + i))
 288                                         return -EFAULT;
 289                                 if (c == 'V')
 290                                         expect_release = 42;
 291                         }
 292                 }
 293                 /* someone wrote to us, we should pat the watchdog */
 294                 at32_wdt_pat();
 295         }
 296         return len;
 297 }
 298
 299 static const struct file_operations at32_wdt_fops = {
 300         .owner          = THIS_MODULE,
 301         .llseek         = no_llseek,
 302         .unlocked_ioctl = at32_wdt_ioctl,
 303         .open           = at32_wdt_open,
 304         .release        = at32_wdt_close,
 305         .write          = at32_wdt_write,
 306 };
 307
 308 static int __init at32_wdt_probe(struct platform_device *pdev)
 309 {
 310         struct resource *regs;
 311         int ret;
 312
 313         if (wdt) {
 314                 dev_dbg(&pdev->dev, "only 1 wdt instance supported.\n");
 315                 return -EBUSY;
 316         }
 317
 318         regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 319         if (!regs) {
 320                 dev_dbg(&pdev->dev, "missing mmio resource\n");
 321                 return -ENXIO;
 322         }
 323
 324         wdt = devm_kzalloc(&pdev->dev, sizeof(struct wdt_at32ap700x),
 325                         GFP_KERNEL);
 326         if (!wdt) {
 327                 dev_dbg(&pdev->dev, "no memory for wdt structure\n");
 328                 return -ENOMEM;
 329         }
 330
 331         wdt->regs = devm_ioremap(&pdev->dev, regs->start, resource_size(regs));
 332         if (!wdt->regs) {
 333                 ret = -ENOMEM;
 334                 dev_dbg(&pdev->dev, "could not map I/O memory\n");
 335                 goto err_free;
 336         }
 337
 338         spin_lock_init(&wdt->io_lock);
 339         wdt->boot_status = at32_wdt_get_status();
 340
 341         /* Work-around for watchdog silicon errata. */
 342         if (wdt->boot_status & WDIOF_CARDRESET) {
 343                 dev_info(&pdev->dev, "CPU must be reset with external "
 344                                 "reset or POR due to silicon errata.\n");
 345                 ret = -EIO;
 346                 goto err_free;
 347         } else {
 348                 wdt->users = 0;
 349         }
 350
 351         wdt->miscdev.minor      = WATCHDOG_MINOR;
 352         wdt->miscdev.name       = "watchdog";
 353         wdt->miscdev.fops       = &at32_wdt_fops;
 354         wdt->miscdev.parent     = &pdev->dev;
 355
 356         platform_set_drvdata(pdev, wdt);
 357
 358         if (at32_wdt_settimeout(timeout)) {
 359                 at32_wdt_settimeout(TIMEOUT_DEFAULT);
 360                 dev_dbg(&pdev->dev,
 361                         "default timeout invalid, set to %d sec.\n",
 362                         TIMEOUT_DEFAULT);
 363         }
 364
 365         ret = misc_register(&wdt->miscdev);
 366         if (ret) {
 367                 dev_dbg(&pdev->dev, "failed to register wdt miscdev\n");
 368                 goto err_free;
 369         }
 370
 371         dev_info(&pdev->dev,
 372                 "AT32AP700X WDT at 0x%p, timeout %d sec (nowayout=%d)\n",
 373                 wdt->regs, wdt->timeout, nowayout);
 374
 375         return 0;
 376
 377 err_free:
 378         wdt = NULL;
 379         return ret;
 380 }
 381
 382 static int __exit at32_wdt_remove(struct platform_device *pdev)
 383 {
 384         if (wdt && platform_get_drvdata(pdev) == wdt) {
 385                 /* Stop the timer before we leave */
 386                 if (!nowayout)
 387                         at32_wdt_stop();
 388
 389                 misc_deregister(&wdt->miscdev);
 390                 wdt = NULL;
 391         }
 392         return 0;
 393 }
 394
 395 static void at32_wdt_shutdown(struct platform_device *pdev)
 396 {
 397         at32_wdt_stop();
 398 }
 399
 400 #ifdef CONFIG_PM
 401 static int at32_wdt_suspend(struct platform_device *pdev, pm_message_t message)
 402 {
 403         at32_wdt_stop();
 404         return 0;
 405 }
 406
 407 static int at32_wdt_resume(struct platform_device *pdev)
 408 {
 409         if (wdt->users)
 410                 at32_wdt_start();
 411         return 0;
 412 }
 413 #else
 414 #define at32_wdt_suspend NULL
 415 #define at32_wdt_resume NULL
 416 #endif
 417
 418 /* work with hotplug and coldplug */
 419 MODULE_ALIAS("platform:at32_wdt");
 420
 421 static struct platform_driver at32_wdt_driver = {
 422         .remove         = __exit_p(at32_wdt_remove),
 423         .suspend        = at32_wdt_suspend,
 424         .resume         = at32_wdt_resume,
 425         .driver         = {
 426                 .name   = "at32_wdt",
 427                 .owner  = THIS_MODULE,
 428         },
 429         .shutdown       = at32_wdt_shutdown,
 430 };
 431
 432 module_platform_driver_probe(at32_wdt_driver, at32_wdt_probe);
 433
 434 MODULE_AUTHOR("Hans-Christian Egtvedt <egtvedt@samfundet.no>");
 435 MODULE_DESCRIPTION("Watchdog driver for Atmel AT32AP700X");
 436 MODULE_LICENSE("GPL");