linux/drivers/watchdog/booke_wdt.c
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   1/*
   2 * Watchdog timer for PowerPC Book-E systems
   3 *
   4 * Author: Matthew McClintock
   5 * Maintainer: Kumar Gala <galak@kernel.crashing.org>
   6 *
   7 * Copyright 2005, 2008, 2010 Freescale Semiconductor Inc.
   8 *
   9 * This program is free software; you can redistribute  it and/or modify it
  10 * under  the terms of  the GNU General  Public License as published by the
  11 * Free Software Foundation;  either version 2 of the  License, or (at your
  12 * option) any later version.
  13 */
  14
  15#include <linux/module.h>
  16#include <linux/fs.h>
  17#include <linux/smp.h>
  18#include <linux/miscdevice.h>
  19#include <linux/notifier.h>
  20#include <linux/watchdog.h>
  21#include <linux/uaccess.h>
  22
  23#include <asm/reg_booke.h>
  24#include <asm/system.h>
  25#include <asm/time.h>
  26#include <asm/div64.h>
  27
  28/* If the kernel parameter wdt=1, the watchdog will be enabled at boot.
  29 * Also, the wdt_period sets the watchdog timer period timeout.
  30 * For E500 cpus the wdt_period sets which bit changing from 0->1 will
  31 * trigger a watchog timeout. This watchdog timeout will occur 3 times, the
  32 * first time nothing will happen, the second time a watchdog exception will
  33 * occur, and the final time the board will reset.
  34 */
  35
  36u32 booke_wdt_enabled;
  37u32 booke_wdt_period = CONFIG_BOOKE_WDT_DEFAULT_TIMEOUT;
  38
  39#ifdef  CONFIG_FSL_BOOKE
  40#define WDTP(x)         ((((x)&0x3)<<30)|(((x)&0x3c)<<15))
  41#define WDTP_MASK       (WDTP(0x3f))
  42#else
  43#define WDTP(x)         (TCR_WP(x))
  44#define WDTP_MASK       (TCR_WP_MASK)
  45#endif
  46
  47static DEFINE_SPINLOCK(booke_wdt_lock);
  48
  49/* For the specified period, determine the number of seconds
  50 * corresponding to the reset time.  There will be a watchdog
  51 * exception at approximately 3/5 of this time.
  52 *
  53 * The formula to calculate this is given by:
  54 * 2.5 * (2^(63-period+1)) / timebase_freq
  55 *
  56 * In order to simplify things, we assume that period is
  57 * at least 1.  This will still result in a very long timeout.
  58 */
  59static unsigned long long period_to_sec(unsigned int period)
  60{
  61        unsigned long long tmp = 1ULL << (64 - period);
  62        unsigned long tmp2 = ppc_tb_freq;
  63
  64        /* tmp may be a very large number and we don't want to overflow,
  65         * so divide the timebase freq instead of multiplying tmp
  66         */
  67        tmp2 = tmp2 / 5 * 2;
  68
  69        do_div(tmp, tmp2);
  70        return tmp;
  71}
  72
  73/*
  74 * This procedure will find the highest period which will give a timeout
  75 * greater than the one required. e.g. for a bus speed of 66666666 and
  76 * and a parameter of 2 secs, then this procedure will return a value of 38.
  77 */
  78static unsigned int sec_to_period(unsigned int secs)
  79{
  80        unsigned int period;
  81        for (period = 63; period > 0; period--) {
  82                if (period_to_sec(period) >= secs)
  83                        return period;
  84        }
  85        return 0;
  86}
  87
  88static void __booke_wdt_ping(void *data)
  89{
  90        mtspr(SPRN_TSR, TSR_ENW|TSR_WIS);
  91}
  92
  93static void booke_wdt_ping(void)
  94{
  95        on_each_cpu(__booke_wdt_ping, NULL, 0);
  96}
  97
  98static void __booke_wdt_enable(void *data)
  99{
 100        u32 val;
 101
 102        /* clear status before enabling watchdog */
 103        __booke_wdt_ping(NULL);
 104        val = mfspr(SPRN_TCR);
 105        val &= ~WDTP_MASK;
 106        val |= (TCR_WIE|TCR_WRC(WRC_CHIP)|WDTP(booke_wdt_period));
 107
 108        mtspr(SPRN_TCR, val);
 109}
 110
 111/**
 112 * booke_wdt_disable - disable the watchdog on the given CPU
 113 *
 114 * This function is called on each CPU.  It disables the watchdog on that CPU.
 115 *
 116 * TCR[WRC] cannot be changed once it has been set to non-zero, but we can
 117 * effectively disable the watchdog by setting its period to the maximum value.
 118 */
 119static void __booke_wdt_disable(void *data)
 120{
 121        u32 val;
 122
 123        val = mfspr(SPRN_TCR);
 124        val &= ~(TCR_WIE | WDTP_MASK);
 125        mtspr(SPRN_TCR, val);
 126
 127        /* clear status to make sure nothing is pending */
 128        __booke_wdt_ping(NULL);
 129
 130}
 131
 132static ssize_t booke_wdt_write(struct file *file, const char __user *buf,
 133                                size_t count, loff_t *ppos)
 134{
 135        booke_wdt_ping();
 136        return count;
 137}
 138
 139static struct watchdog_info ident = {
 140        .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
 141        .identity = "PowerPC Book-E Watchdog",
 142};
 143
 144static long booke_wdt_ioctl(struct file *file,
 145                                unsigned int cmd, unsigned long arg)
 146{
 147        u32 tmp = 0;
 148        u32 __user *p = (u32 __user *)arg;
 149
 150        switch (cmd) {
 151        case WDIOC_GETSUPPORT:
 152                if (copy_to_user((void *)arg, &ident, sizeof(ident)))
 153                        return -EFAULT;
 154        case WDIOC_GETSTATUS:
 155                return put_user(0, p);
 156        case WDIOC_GETBOOTSTATUS:
 157                /* XXX: something is clearing TSR */
 158                tmp = mfspr(SPRN_TSR) & TSR_WRS(3);
 159                /* returns CARDRESET if last reset was caused by the WDT */
 160                return (tmp ? WDIOF_CARDRESET : 0);
 161        case WDIOC_SETOPTIONS:
 162                if (get_user(tmp, p))
 163                        return -EINVAL;
 164                if (tmp == WDIOS_ENABLECARD) {
 165                        booke_wdt_ping();
 166                        break;
 167                } else
 168                        return -EINVAL;
 169                return 0;
 170        case WDIOC_KEEPALIVE:
 171                booke_wdt_ping();
 172                return 0;
 173        case WDIOC_SETTIMEOUT:
 174                if (get_user(tmp, p))
 175                        return -EFAULT;
 176#ifdef  CONFIG_FSL_BOOKE
 177                /* period of 1 gives the largest possible timeout */
 178                if (tmp > period_to_sec(1))
 179                        return -EINVAL;
 180                booke_wdt_period = sec_to_period(tmp);
 181#else
 182                booke_wdt_period = tmp;
 183#endif
 184                mtspr(SPRN_TCR, (mfspr(SPRN_TCR) & ~WDTP_MASK) |
 185                                                WDTP(booke_wdt_period));
 186                return 0;
 187        case WDIOC_GETTIMEOUT:
 188                return put_user(booke_wdt_period, p);
 189        default:
 190                return -ENOTTY;
 191        }
 192
 193        return 0;
 194}
 195
 196static int booke_wdt_open(struct inode *inode, struct file *file)
 197{
 198        spin_lock(&booke_wdt_lock);
 199        if (booke_wdt_enabled == 0) {
 200                booke_wdt_enabled = 1;
 201                on_each_cpu(__booke_wdt_enable, NULL, 0);
 202                printk(KERN_INFO
 203                      "PowerPC Book-E Watchdog Timer Enabled (wdt_period=%d)\n",
 204                                booke_wdt_period);
 205        }
 206        spin_unlock(&booke_wdt_lock);
 207
 208        return nonseekable_open(inode, file);
 209}
 210
 211static int booke_wdt_release(struct inode *inode, struct file *file)
 212{
 213        on_each_cpu(__booke_wdt_disable, NULL, 0);
 214        booke_wdt_enabled = 0;
 215
 216        return 0;
 217}
 218
 219static const struct file_operations booke_wdt_fops = {
 220        .owner = THIS_MODULE,
 221        .llseek = no_llseek,
 222        .write = booke_wdt_write,
 223        .unlocked_ioctl = booke_wdt_ioctl,
 224        .open = booke_wdt_open,
 225        .release = booke_wdt_release,
 226};
 227
 228static struct miscdevice booke_wdt_miscdev = {
 229        .minor = WATCHDOG_MINOR,
 230        .name = "watchdog",
 231        .fops = &booke_wdt_fops,
 232};
 233
 234static void __exit booke_wdt_exit(void)
 235{
 236        misc_deregister(&booke_wdt_miscdev);
 237}
 238
 239static int __init booke_wdt_init(void)
 240{
 241        int ret = 0;
 242
 243        printk(KERN_INFO "PowerPC Book-E Watchdog Timer Loaded\n");
 244        ident.firmware_version = cur_cpu_spec->pvr_value;
 245
 246        ret = misc_register(&booke_wdt_miscdev);
 247        if (ret) {
 248                printk(KERN_CRIT "Cannot register miscdev on minor=%d: %d\n",
 249                                WATCHDOG_MINOR, ret);
 250                return ret;
 251        }
 252
 253        spin_lock(&booke_wdt_lock);
 254        if (booke_wdt_enabled == 1) {
 255                printk(KERN_INFO
 256                      "PowerPC Book-E Watchdog Timer Enabled (wdt_period=%d)\n",
 257                                booke_wdt_period);
 258                on_each_cpu(__booke_wdt_enable, NULL, 0);
 259        }
 260        spin_unlock(&booke_wdt_lock);
 261
 262        return ret;
 263}
 264
 265module_init(booke_wdt_init);
 266module_exit(booke_wdt_exit);
 267
 268MODULE_DESCRIPTION("PowerPC Book-E watchdog driver");
 269MODULE_LICENSE("GPL");
 270