drivers/watchdog/gef_wdt.c

   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 #include <linux/kernel.h>
  28 #include <linux/compiler.h>
  29 #include <linux/init.h>
  30 #include <linux/module.h>
  31 #include <linux/miscdevice.h>
  32 #include <linux/watchdog.h>
  33 #include <linux/fs.h>
  34 #include <linux/of.h>
  35 #include <linux/of_platform.h>
  36 #include <linux/io.h>
  37 #include <linux/uaccess.h>
  38
  39 #include <sysdev/fsl_soc.h>
  40
  41 /*
  42  * The watchdog configuration register contains a pair of 2-bit fields,
  43  *   1.  a reload field, bits 27-26, which triggers a reload of
  44  *       the countdown register, and
  45  *   2.  an enable field, bits 25-24, which toggles between
  46  *       enabling and disabling the watchdog timer.
  47  * Bit 31 is a read-only field which indicates whether the
  48  * watchdog timer is currently enabled.
  49  *
  50  * The low 24 bits contain the timer reload value.
  51  */
  52 #define GEF_WDC_ENABLE_SHIFT    24
  53 #define GEF_WDC_SERVICE_SHIFT   26
  54 #define GEF_WDC_ENABLED_SHIFT   31
  55
  56 #define GEF_WDC_ENABLED_TRUE    1
  57 #define GEF_WDC_ENABLED_FALSE   0
  58
  59 /* Flags bits */
  60 #define GEF_WDOG_FLAG_OPENED    0
  61
  62 static unsigned long wdt_flags;
  63 static int wdt_status;
  64 static void __iomem *gef_wdt_regs;
  65 static int gef_wdt_timeout;
  66 static int gef_wdt_count;
  67 static unsigned int bus_clk;
  68 static char expect_close;
  69 static DEFINE_SPINLOCK(gef_wdt_spinlock);
  70
  71 static int nowayout = WATCHDOG_NOWAYOUT;
  72 module_param(nowayout, int, 0);
  73 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
  74         __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  75
  76
  77 static int gef_wdt_toggle_wdc(int enabled_predicate, int field_shift)
  78 {
  79         u32 data;
  80         u32 enabled;
  81         int ret = 0;
  82
  83         spin_lock(&gef_wdt_spinlock);
  84         data = ioread32be(gef_wdt_regs);
  85         enabled = (data >> GEF_WDC_ENABLED_SHIFT) & 1;
  86
  87         /* only toggle the requested field if enabled state matches predicate */
  88         if ((enabled ^ enabled_predicate) == 0) {
  89                 /* We write a 1, then a 2 -- to the appropriate field */
  90                 data = (1 << field_shift) | gef_wdt_count;
  91                 iowrite32be(data, gef_wdt_regs);
  92
  93                 data = (2 << field_shift) | gef_wdt_count;
  94                 iowrite32be(data, gef_wdt_regs);
  95                 ret = 1;
  96         }
  97         spin_unlock(&gef_wdt_spinlock);
  98
  99         return ret;
 100 }
 101
 102 static void gef_wdt_service(void)
 103 {
 104         gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
 105                 GEF_WDC_SERVICE_SHIFT);
 106 }
 107
 108 static void gef_wdt_handler_enable(void)
 109 {
 110         if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_FALSE,
 111                                    GEF_WDC_ENABLE_SHIFT)) {
 112                 gef_wdt_service();
 113                 printk(KERN_NOTICE "gef_wdt: watchdog activated\n");
 114         }
 115 }
 116
 117 static void gef_wdt_handler_disable(void)
 118 {
 119         if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
 120                                    GEF_WDC_ENABLE_SHIFT))
 121                 printk(KERN_NOTICE "gef_wdt: watchdog deactivated\n");
 122 }
 123
 124 static void gef_wdt_set_timeout(unsigned int timeout)
 125 {
 126         /* maximum bus cycle count is 0xFFFFFFFF */
 127         if (timeout > 0xFFFFFFFF / bus_clk)
 128                 timeout = 0xFFFFFFFF / bus_clk;
 129
 130         /* Register only holds upper 24 bits, bit shifted into lower 24 */
 131         gef_wdt_count = (timeout * bus_clk) >> 8;
 132         gef_wdt_timeout = timeout;
 133 }
 134
 135
 136 static ssize_t gef_wdt_write(struct file *file, const char __user *data,
 137                                  size_t len, loff_t *ppos)
 138 {
 139         if (len) {
 140                 if (!nowayout) {
 141                         size_t i;
 142
 143                         expect_close = 0;
 144
 145                         for (i = 0; i != len; i++) {
 146                                 char c;
 147                                 if (get_user(c, data + i))
 148                                         return -EFAULT;
 149                                 if (c == 'V')
 150                                         expect_close = 42;
 151                         }
 152                 }
 153                 gef_wdt_service();
 154         }
 155
 156         return len;
 157 }
 158
 159 static long gef_wdt_ioctl(struct file *file, unsigned int cmd,
 160                                                         unsigned long arg)
 161 {
 162         int timeout;
 163         int options;
 164         void __user *argp = (void __user *)arg;
 165         static const struct watchdog_info info = {
 166                 .options =      WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
 167                                 WDIOF_KEEPALIVEPING,
 168                 .firmware_version = 0,
 169                 .identity = "GE watchdog",
 170         };
 171
 172         switch (cmd) {
 173         case WDIOC_GETSUPPORT:
 174                 if (copy_to_user(argp, &info, sizeof(info)))
 175                         return -EFAULT;
 176                 break;
 177
 178         case WDIOC_GETSTATUS:
 179         case WDIOC_GETBOOTSTATUS:
 180                 if (put_user(wdt_status, (int __user *)argp))
 181                         return -EFAULT;
 182                 wdt_status &= ~WDIOF_KEEPALIVEPING;
 183                 break;
 184
 185         case WDIOC_SETOPTIONS:
 186                 if (get_user(options, (int __user *)argp))
 187                         return -EFAULT;
 188
 189                 if (options & WDIOS_DISABLECARD)
 190                         gef_wdt_handler_disable();
 191
 192                 if (options & WDIOS_ENABLECARD)
 193                         gef_wdt_handler_enable();
 194                 break;
 195
 196         case WDIOC_KEEPALIVE:
 197                 gef_wdt_service();
 198                 wdt_status |= WDIOF_KEEPALIVEPING;
 199                 break;
 200
 201         case WDIOC_SETTIMEOUT:
 202                 if (get_user(timeout, (int __user *)argp))
 203                         return -EFAULT;
 204                 gef_wdt_set_timeout(timeout);
 205                 /* Fall through */
 206
 207         case WDIOC_GETTIMEOUT:
 208                 if (put_user(gef_wdt_timeout, (int __user *)argp))
 209                         return -EFAULT;
 210                 break;
 211
 212         default:
 213                 return -ENOTTY;
 214         }
 215
 216         return 0;
 217 }
 218
 219 static int gef_wdt_open(struct inode *inode, struct file *file)
 220 {
 221         if (test_and_set_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags))
 222                 return -EBUSY;
 223
 224         if (nowayout)
 225                 __module_get(THIS_MODULE);
 226
 227         gef_wdt_handler_enable();
 228
 229         return nonseekable_open(inode, file);
 230 }
 231
 232 static int gef_wdt_release(struct inode *inode, struct file *file)
 233 {
 234         if (expect_close == 42)
 235                 gef_wdt_handler_disable();
 236         else {
 237                 printk(KERN_CRIT
 238                        "gef_wdt: unexpected close, not stopping timer!\n");
 239                 gef_wdt_service();
 240         }
 241         expect_close = 0;
 242
 243         clear_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags);
 244
 245         return 0;
 246 }
 247
 248 static const struct file_operations gef_wdt_fops = {
 249         .owner = THIS_MODULE,
 250         .llseek = no_llseek,
 251         .write = gef_wdt_write,
 252         .unlocked_ioctl = gef_wdt_ioctl,
 253         .open = gef_wdt_open,
 254         .release = gef_wdt_release,
 255 };
 256
 257 static struct miscdevice gef_wdt_miscdev = {
 258         .minor = WATCHDOG_MINOR,
 259         .name = "watchdog",
 260         .fops = &gef_wdt_fops,
 261 };
 262
 263
 264 static int __devinit gef_wdt_probe(struct platform_device *dev,
 265         const struct of_device_id *match)
 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
 288 static int __devexit 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
 299 static const struct of_device_id gef_wdt_ids[] = {
 300         {
 301                 .compatible = "gef,fpga-wdt",
 302         },
 303         {},
 304 };
 305
 306 static struct of_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
 315 static int __init gef_wdt_init(void)
 316 {
 317         printk(KERN_INFO "GE watchdog driver\n");
 318         return of_register_platform_driver(&gef_wdt_driver);
 319 }
 320
 321 static void __exit gef_wdt_exit(void)
 322 {
 323         of_unregister_platform_driver(&gef_wdt_driver);
 324 }
 325
 326 module_init(gef_wdt_init);
 327 module_exit(gef_wdt_exit);
 328
 329 MODULE_AUTHOR("Martyn Welch <martyn.welch@ge.com>");
 330 MODULE_DESCRIPTION("GE watchdog driver");
 331 MODULE_LICENSE("GPL");
 332 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
 333 MODULE_ALIAS("platform: gef_wdt");