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