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_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
  64 static unsigned long wdt_flags;
  65 static int wdt_status;
  66 static void __iomem *gef_wdt_regs;
  67 static int gef_wdt_timeout;
  68 static int gef_wdt_count;
  69 static unsigned int bus_clk;
  70 static char expect_close;
  71 static DEFINE_SPINLOCK(gef_wdt_spinlock);
  72
  73 static bool nowayout = WATCHDOG_NOWAYOUT;
  74 module_param(nowayout, bool, 0);
  75 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
  76         __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  77
  78
  79 static 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
 104 static void gef_wdt_service(void)
 105 {
 106         gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
 107                 GEF_WDC_SERVICE_SHIFT);
 108 }
 109
 110 static 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
 119 static 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
 126 static 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
 138 static 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
 161 static 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
 221 static 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
 234 static 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
 249 static 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
 258 static struct miscdevice gef_wdt_miscdev = {
 259         .minor = WATCHDOG_MINOR,
 260         .name = "watchdog",
 261         .fops = &gef_wdt_fops,
 262 };
 263
 264
 265 static 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
 288 static 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
 299 static const struct of_device_id gef_wdt_ids[] = {
 300         {
 301                 .compatible = "gef,fpga-wdt",
 302         },
 303         {},
 304 };
 305
 306 static 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         .remove         = gef_wdt_remove,
 314 };
 315
 316 static int __init gef_wdt_init(void)
 317 {
 318         pr_info("GE watchdog driver\n");
 319         return platform_driver_register(&gef_wdt_driver);
 320 }
 321
 322 static void __exit gef_wdt_exit(void)
 323 {
 324         platform_driver_unregister(&gef_wdt_driver);
 325 }
 326
 327 module_init(gef_wdt_init);
 328 module_exit(gef_wdt_exit);
 329
 330 MODULE_AUTHOR("Martyn Welch <martyn.welch@ge.com>");
 331 MODULE_DESCRIPTION("GE watchdog driver");
 332 MODULE_LICENSE("GPL");
 333 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
 334 MODULE_ALIAS("platform:gef_wdt");