linux/drivers/watchdog/gef_wdt.c
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   1/*
   2 * GE watchdog userspace interface
   3 *
   4 * Author:  Martyn Welch <martyn.welch@ge.com>
   5 *
   6 * Copyright 2008 GE Intelligent Platforms Embedded Systems, Inc.
   7 *
   8 * This program is free software; you can redistribute  it and/or modify it
   9 * under  the terms of  the GNU General  Public License as published by the
  10 * Free Software Foundation;  either version 2 of the  License, or (at your
  11 * option) any later version.
  12 *
  13 * Based on: mv64x60_wdt.c (MV64X60 watchdog userspace interface)
  14 *   Author: James Chapman <jchapman@katalix.com>
  15 */
  16
  17/* TODO:
  18 * This driver does not provide support for the hardwares capability of sending
  19 * an interrupt at a programmable threshold.
  20 *
  21 * This driver currently can only support 1 watchdog - there are 2 in the
  22 * hardware that this driver supports. Thus one could be configured as a
  23 * process-based watchdog (via /dev/watchdog), the second (using the interrupt
  24 * capabilities) a kernel-based watchdog.
  25 */
  26
  27#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  28
  29#include <linux/kernel.h>
  30#include <linux/compiler.h>
  31#include <linux/init.h>
  32#include <linux/module.h>
  33#include <linux/miscdevice.h>
  34#include <linux/watchdog.h>
  35#include <linux/fs.h>
  36#include <linux/of.h>
  37#include <linux/of_platform.h>
  38#include <linux/io.h>
  39#include <linux/uaccess.h>
  40
  41#include <sysdev/fsl_soc.h>
  42
  43/*
  44 * The watchdog configuration register contains a pair of 2-bit fields,
  45 *   1.  a reload field, bits 27-26, which triggers a reload of
  46 *       the countdown register, and
  47 *   2.  an enable field, bits 25-24, which toggles between
  48 *       enabling and disabling the watchdog timer.
  49 * Bit 31 is a read-only field which indicates whether the
  50 * watchdog timer is currently enabled.
  51 *
  52 * The low 24 bits contain the timer reload value.
  53 */
  54#define GEF_WDC_ENABLE_SHIFT    24
  55#define GEF_WDC_SERVICE_SHIFT   26
  56#define GEF_WDC_ENABLED_SHIFT   31
  57
  58#define GEF_WDC_ENABLED_TRUE    1
  59#define GEF_WDC_ENABLED_FALSE   0
  60
  61/* Flags bits */
  62#define GEF_WDOG_FLAG_OPENED    0
  63
  64static unsigned long wdt_flags;
  65static int wdt_status;
  66static void __iomem *gef_wdt_regs;
  67static int gef_wdt_timeout;
  68static int gef_wdt_count;
  69static unsigned int bus_clk;
  70static char expect_close;
  71static DEFINE_SPINLOCK(gef_wdt_spinlock);
  72
  73static bool nowayout = WATCHDOG_NOWAYOUT;
  74module_param(nowayout, bool, 0);
  75MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
  76        __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  77
  78
  79static int gef_wdt_toggle_wdc(int enabled_predicate, int field_shift)
  80{
  81        u32 data;
  82        u32 enabled;
  83        int ret = 0;
  84
  85        spin_lock(&gef_wdt_spinlock);
  86        data = ioread32be(gef_wdt_regs);
  87        enabled = (data >> GEF_WDC_ENABLED_SHIFT) & 1;
  88
  89        /* only toggle the requested field if enabled state matches predicate */
  90        if ((enabled ^ enabled_predicate) == 0) {
  91                /* We write a 1, then a 2 -- to the appropriate field */
  92                data = (1 << field_shift) | gef_wdt_count;
  93                iowrite32be(data, gef_wdt_regs);
  94
  95                data = (2 << field_shift) | gef_wdt_count;
  96                iowrite32be(data, gef_wdt_regs);
  97                ret = 1;
  98        }
  99        spin_unlock(&gef_wdt_spinlock);
 100
 101        return ret;
 102}
 103
 104static void gef_wdt_service(void)
 105{
 106        gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
 107                GEF_WDC_SERVICE_SHIFT);
 108}
 109
 110static void gef_wdt_handler_enable(void)
 111{
 112        if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_FALSE,
 113                                   GEF_WDC_ENABLE_SHIFT)) {
 114                gef_wdt_service();
 115                pr_notice("watchdog activated\n");
 116        }
 117}
 118
 119static void gef_wdt_handler_disable(void)
 120{
 121        if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
 122                                   GEF_WDC_ENABLE_SHIFT))
 123                pr_notice("watchdog deactivated\n");
 124}
 125
 126static void gef_wdt_set_timeout(unsigned int timeout)
 127{
 128        /* maximum bus cycle count is 0xFFFFFFFF */
 129        if (timeout > 0xFFFFFFFF / bus_clk)
 130                timeout = 0xFFFFFFFF / bus_clk;
 131
 132        /* Register only holds upper 24 bits, bit shifted into lower 24 */
 133        gef_wdt_count = (timeout * bus_clk) >> 8;
 134        gef_wdt_timeout = timeout;
 135}
 136
 137
 138static ssize_t gef_wdt_write(struct file *file, const char __user *data,
 139                                 size_t len, loff_t *ppos)
 140{
 141        if (len) {
 142                if (!nowayout) {
 143                        size_t i;
 144
 145                        expect_close = 0;
 146
 147                        for (i = 0; i != len; i++) {
 148                                char c;
 149                                if (get_user(c, data + i))
 150                                        return -EFAULT;
 151                                if (c == 'V')
 152                                        expect_close = 42;
 153                        }
 154                }
 155                gef_wdt_service();
 156        }
 157
 158        return len;
 159}
 160
 161static long gef_wdt_ioctl(struct file *file, unsigned int cmd,
 162                                                        unsigned long arg)
 163{
 164        int timeout;
 165        int options;
 166        void __user *argp = (void __user *)arg;
 167        static const struct watchdog_info info = {
 168                .options =      WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
 169                                WDIOF_KEEPALIVEPING,
 170                .firmware_version = 0,
 171                .identity = "GE watchdog",
 172        };
 173
 174        switch (cmd) {
 175        case WDIOC_GETSUPPORT:
 176                if (copy_to_user(argp, &info, sizeof(info)))
 177                        return -EFAULT;
 178                break;
 179
 180        case WDIOC_GETSTATUS:
 181        case WDIOC_GETBOOTSTATUS:
 182                if (put_user(wdt_status, (int __user *)argp))
 183                        return -EFAULT;
 184                wdt_status &= ~WDIOF_KEEPALIVEPING;
 185                break;
 186
 187        case WDIOC_SETOPTIONS:
 188                if (get_user(options, (int __user *)argp))
 189                        return -EFAULT;
 190
 191                if (options & WDIOS_DISABLECARD)
 192                        gef_wdt_handler_disable();
 193
 194                if (options & WDIOS_ENABLECARD)
 195                        gef_wdt_handler_enable();
 196                break;
 197
 198        case WDIOC_KEEPALIVE:
 199                gef_wdt_service();
 200                wdt_status |= WDIOF_KEEPALIVEPING;
 201                break;
 202
 203        case WDIOC_SETTIMEOUT:
 204                if (get_user(timeout, (int __user *)argp))
 205                        return -EFAULT;
 206                gef_wdt_set_timeout(timeout);
 207                /* Fall through */
 208
 209        case WDIOC_GETTIMEOUT:
 210                if (put_user(gef_wdt_timeout, (int __user *)argp))
 211                        return -EFAULT;
 212                break;
 213
 214        default:
 215                return -ENOTTY;
 216        }
 217
 218        return 0;
 219}
 220
 221static int gef_wdt_open(struct inode *inode, struct file *file)
 222{
 223        if (test_and_set_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags))
 224                return -EBUSY;
 225
 226        if (nowayout)
 227                __module_get(THIS_MODULE);
 228
 229        gef_wdt_handler_enable();
 230
 231        return nonseekable_open(inode, file);
 232}
 233
 234static int gef_wdt_release(struct inode *inode, struct file *file)
 235{
 236        if (expect_close == 42)
 237                gef_wdt_handler_disable();
 238        else {
 239                pr_crit("unexpected close, not stopping timer!\n");
 240                gef_wdt_service();
 241        }
 242        expect_close = 0;
 243
 244        clear_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags);
 245
 246        return 0;
 247}
 248
 249static const struct file_operations gef_wdt_fops = {
 250        .owner = THIS_MODULE,
 251        .llseek = no_llseek,
 252        .write = gef_wdt_write,
 253        .unlocked_ioctl = gef_wdt_ioctl,
 254        .open = gef_wdt_open,
 255        .release = gef_wdt_release,
 256};
 257
 258static struct miscdevice gef_wdt_miscdev = {
 259        .minor = WATCHDOG_MINOR,
 260        .name = "watchdog",
 261        .fops = &gef_wdt_fops,
 262};
 263
 264
 265static int gef_wdt_probe(struct platform_device *dev)
 266{
 267        int timeout = 10;
 268        u32 freq;
 269
 270        bus_clk = 133; /* in MHz */
 271
 272        freq = fsl_get_sys_freq();
 273        if (freq != -1)
 274                bus_clk = freq;
 275
 276        /* Map devices registers into memory */
 277        gef_wdt_regs = of_iomap(dev->dev.of_node, 0);
 278        if (gef_wdt_regs == NULL)
 279                return -ENOMEM;
 280
 281        gef_wdt_set_timeout(timeout);
 282
 283        gef_wdt_handler_disable();      /* in case timer was already running */
 284
 285        return misc_register(&gef_wdt_miscdev);
 286}
 287
 288static int gef_wdt_remove(struct platform_device *dev)
 289{
 290        misc_deregister(&gef_wdt_miscdev);
 291
 292        gef_wdt_handler_disable();
 293
 294        iounmap(gef_wdt_regs);
 295
 296        return 0;
 297}
 298
 299static const struct of_device_id gef_wdt_ids[] = {
 300        {
 301                .compatible = "gef,fpga-wdt",
 302        },
 303        {},
 304};
 305
 306static struct platform_driver gef_wdt_driver = {
 307        .driver = {
 308                .name = "gef_wdt",
 309                .owner = THIS_MODULE,
 310                .of_match_table = gef_wdt_ids,
 311        },
 312        .probe          = gef_wdt_probe,
 313};
 314
 315static int __init gef_wdt_init(void)
 316{
 317        pr_info("GE watchdog driver\n");
 318        return platform_driver_register(&gef_wdt_driver);
 319}
 320
 321static void __exit gef_wdt_exit(void)
 322{
 323        platform_driver_unregister(&gef_wdt_driver);
 324}
 325
 326module_init(gef_wdt_init);
 327module_exit(gef_wdt_exit);
 328
 329MODULE_AUTHOR("Martyn Welch <martyn.welch@ge.com>");
 330MODULE_DESCRIPTION("GE watchdog driver");
 331MODULE_LICENSE("GPL");
 332MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
 333MODULE_ALIAS("platform:gef_wdt");
 334
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