linux/drivers/watchdog/at32ap700x_wdt.c
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   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 */
  42static int timeout =  TIMEOUT_DEFAULT;
  43module_param(timeout, int, 0);
  44MODULE_PARM_DESC(timeout,
  45                "Timeout value. Limited to be 1 or 2 seconds. (default="
  46                __MODULE_STRING(TIMEOUT_DEFAULT) ")");
  47
  48static bool nowayout = WATCHDOG_NOWAYOUT;
  49module_param(nowayout, bool, 0);
  50MODULE_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
  76struct 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
  85static struct wdt_at32ap700x *wdt;
  86static char expect_release;
  87
  88/*
  89 * Disable the watchdog.
  90 */
  91static 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 */
 105static 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 */
 123static 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 */
 133static 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 */
 145static 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 */
 162static 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 */
 182static 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
 206static 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 */
 216static 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
 267static 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
 299static 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
 308static 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 = kzalloc(sizeof(struct wdt_at32ap700x), GFP_KERNEL);
 325        if (!wdt) {
 326                dev_dbg(&pdev->dev, "no memory for wdt structure\n");
 327                return -ENOMEM;
 328        }
 329
 330        wdt->regs = ioremap(regs->start, resource_size(regs));
 331        if (!wdt->regs) {
 332                ret = -ENOMEM;
 333                dev_dbg(&pdev->dev, "could not map I/O memory\n");
 334                goto err_free;
 335        }
 336
 337        spin_lock_init(&wdt->io_lock);
 338        wdt->boot_status = at32_wdt_get_status();
 339
 340        /* Work-around for watchdog silicon errata. */
 341        if (wdt->boot_status & WDIOF_CARDRESET) {
 342                dev_info(&pdev->dev, "CPU must be reset with external "
 343                                "reset or POR due to silicon errata.\n");
 344                ret = -EIO;
 345                goto err_iounmap;
 346        } else {
 347                wdt->users = 0;
 348        }
 349
 350        wdt->miscdev.minor      = WATCHDOG_MINOR;
 351        wdt->miscdev.name       = "watchdog";
 352        wdt->miscdev.fops       = &at32_wdt_fops;
 353        wdt->miscdev.parent     = &pdev->dev;
 354
 355        platform_set_drvdata(pdev, wdt);
 356
 357        if (at32_wdt_settimeout(timeout)) {
 358                at32_wdt_settimeout(TIMEOUT_DEFAULT);
 359                dev_dbg(&pdev->dev,
 360                        "default timeout invalid, set to %d sec.\n",
 361                        TIMEOUT_DEFAULT);
 362        }
 363
 364        ret = misc_register(&wdt->miscdev);
 365        if (ret) {
 366                dev_dbg(&pdev->dev, "failed to register wdt miscdev\n");
 367                goto err_register;
 368        }
 369
 370        dev_info(&pdev->dev,
 371                "AT32AP700X WDT at 0x%p, timeout %d sec (nowayout=%d)\n",
 372                wdt->regs, wdt->timeout, nowayout);
 373
 374        return 0;
 375
 376err_register:
 377        platform_set_drvdata(pdev, NULL);
 378err_iounmap:
 379        iounmap(wdt->regs);
 380err_free:
 381        kfree(wdt);
 382        wdt = NULL;
 383        return ret;
 384}
 385
 386static int __exit at32_wdt_remove(struct platform_device *pdev)
 387{
 388        if (wdt && platform_get_drvdata(pdev) == wdt) {
 389                /* Stop the timer before we leave */
 390                if (!nowayout)
 391                        at32_wdt_stop();
 392
 393                misc_deregister(&wdt->miscdev);
 394                iounmap(wdt->regs);
 395                kfree(wdt);
 396                wdt = NULL;
 397                platform_set_drvdata(pdev, NULL);
 398        }
 399        return 0;
 400}
 401
 402static void at32_wdt_shutdown(struct platform_device *pdev)
 403{
 404        at32_wdt_stop();
 405}
 406
 407#ifdef CONFIG_PM
 408static int at32_wdt_suspend(struct platform_device *pdev, pm_message_t message)
 409{
 410        at32_wdt_stop();
 411        return 0;
 412}
 413
 414static int at32_wdt_resume(struct platform_device *pdev)
 415{
 416        if (wdt->users)
 417                at32_wdt_start();
 418        return 0;
 419}
 420#else
 421#define at32_wdt_suspend NULL
 422#define at32_wdt_resume NULL
 423#endif
 424
 425/* work with hotplug and coldplug */
 426MODULE_ALIAS("platform:at32_wdt");
 427
 428static struct platform_driver at32_wdt_driver = {
 429        .remove         = __exit_p(at32_wdt_remove),
 430        .suspend        = at32_wdt_suspend,
 431        .resume         = at32_wdt_resume,
 432        .driver         = {
 433                .name   = "at32_wdt",
 434                .owner  = THIS_MODULE,
 435        },
 436        .shutdown       = at32_wdt_shutdown,
 437};
 438
 439static int __init at32_wdt_init(void)
 440{
 441        return platform_driver_probe(&at32_wdt_driver, at32_wdt_probe);
 442}
 443module_init(at32_wdt_init);
 444
 445static void __exit at32_wdt_exit(void)
 446{
 447        platform_driver_unregister(&at32_wdt_driver);
 448}
 449module_exit(at32_wdt_exit);
 450
 451MODULE_AUTHOR("Hans-Christian Egtvedt <egtvedt@samfundet.no>");
 452MODULE_DESCRIPTION("Watchdog driver for Atmel AT32AP700X");
 453MODULE_LICENSE("GPL");
 454MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
 455
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