drivers/watchdog/gef_wdt.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * GE watchdog userspace interface
   4  *
   5  * Author:  Martyn Welch <martyn.welch@ge.com>
   6  *
   7  * Copyright 2008 GE Intelligent Platforms Embedded Systems, Inc.
   8  *
   9  * Based on: mv64x60_wdt.c (MV64X60 watchdog userspace interface)
  10  *   Author: James Chapman <jchapman@katalix.com>
  11  */
  12
  13 /* TODO:
  14  * This driver does not provide support for the hardwares capability of sending
  15  * an interrupt at a programmable threshold.
  16  *
  17  * This driver currently can only support 1 watchdog - there are 2 in the
  18  * hardware that this driver supports. Thus one could be configured as a
  19  * process-based watchdog (via /dev/watchdog), the second (using the interrupt
  20  * capabilities) a kernel-based watchdog.
  21  */
  22
  23 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  24
  25 #include <linux/kernel.h>
  26 #include <linux/compiler.h>
  27 #include <linux/init.h>
  28 #include <linux/module.h>
  29 #include <linux/miscdevice.h>
  30 #include <linux/watchdog.h>
  31 #include <linux/fs.h>
  32 #include <linux/of.h>
  33 #include <linux/of_address.h>
  34 #include <linux/of_platform.h>
  35 #include <linux/io.h>
  36 #include <linux/uaccess.h>
  37
  38 #include <sysdev/fsl_soc.h>
  39
  40 /*
  41  * The watchdog configuration register contains a pair of 2-bit fields,
  42  *   1.  a reload field, bits 27-26, which triggers a reload of
  43  *       the countdown register, and
  44  *   2.  an enable field, bits 25-24, which toggles between
  45  *       enabling and disabling the watchdog timer.
  46  * Bit 31 is a read-only field which indicates whether the
  47  * watchdog timer is currently enabled.
  48  *
  49  * The low 24 bits contain the timer reload value.
  50  */
  51 #define GEF_WDC_ENABLE_SHIFT    24
  52 #define GEF_WDC_SERVICE_SHIFT   26
  53 #define GEF_WDC_ENABLED_SHIFT   31
  54
  55 #define GEF_WDC_ENABLED_TRUE    1
  56 #define GEF_WDC_ENABLED_FALSE   0
  57
  58 /* Flags bits */
  59 #define GEF_WDOG_FLAG_OPENED    0
  60
  61 static unsigned long wdt_flags;
  62 static int wdt_status;
  63 static void __iomem *gef_wdt_regs;
  64 static int gef_wdt_timeout;
  65 static int gef_wdt_count;
  66 static unsigned int bus_clk;
  67 static char expect_close;
  68 static DEFINE_SPINLOCK(gef_wdt_spinlock);
  69
  70 static bool nowayout = WATCHDOG_NOWAYOUT;
  71 module_param(nowayout, bool, 0);
  72 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
  73         __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  74
  75
  76 static int gef_wdt_toggle_wdc(int enabled_predicate, int field_shift)
  77 {
  78         u32 data;
  79         u32 enabled;
  80         int ret = 0;
  81
  82         spin_lock(&gef_wdt_spinlock);
  83         data = ioread32be(gef_wdt_regs);
  84         enabled = (data >> GEF_WDC_ENABLED_SHIFT) & 1;
  85
  86         /* only toggle the requested field if enabled state matches predicate */
  87         if ((enabled ^ enabled_predicate) == 0) {
  88                 /* We write a 1, then a 2 -- to the appropriate field */
  89                 data = (1 << field_shift) | gef_wdt_count;
  90                 iowrite32be(data, gef_wdt_regs);
  91
  92                 data = (2 << field_shift) | gef_wdt_count;
  93                 iowrite32be(data, gef_wdt_regs);
  94                 ret = 1;
  95         }
  96         spin_unlock(&gef_wdt_spinlock);
  97
  98         return ret;
  99 }
 100
 101 static void gef_wdt_service(void)
 102 {
 103         gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
 104                 GEF_WDC_SERVICE_SHIFT);
 105 }
 106
 107 static void gef_wdt_handler_enable(void)
 108 {
 109         if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_FALSE,
 110                                    GEF_WDC_ENABLE_SHIFT)) {
 111                 gef_wdt_service();
 112                 pr_notice("watchdog activated\n");
 113         }
 114 }
 115
 116 static void gef_wdt_handler_disable(void)
 117 {
 118         if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
 119                                    GEF_WDC_ENABLE_SHIFT))
 120                 pr_notice("watchdog deactivated\n");
 121 }
 122
 123 static void gef_wdt_set_timeout(unsigned int timeout)
 124 {
 125         /* maximum bus cycle count is 0xFFFFFFFF */
 126         if (timeout > 0xFFFFFFFF / bus_clk)
 127                 timeout = 0xFFFFFFFF / bus_clk;
 128
 129         /* Register only holds upper 24 bits, bit shifted into lower 24 */
 130         gef_wdt_count = (timeout * bus_clk) >> 8;
 131         gef_wdt_timeout = timeout;
 132 }
 133
 134
 135 static ssize_t gef_wdt_write(struct file *file, const char __user *data,
 136                                  size_t len, loff_t *ppos)
 137 {
 138         if (len) {
 139                 if (!nowayout) {
 140                         size_t i;
 141
 142                         expect_close = 0;
 143
 144                         for (i = 0; i != len; i++) {
 145                                 char c;
 146                                 if (get_user(c, data + i))
 147                                         return -EFAULT;
 148                                 if (c == 'V')
 149                                         expect_close = 42;
 150                         }
 151                 }
 152                 gef_wdt_service();
 153         }
 154
 155         return len;
 156 }
 157
 158 static long gef_wdt_ioctl(struct file *file, unsigned int cmd,
 159                                                         unsigned long arg)
 160 {
 161         int timeout;
 162         int options;
 163         void __user *argp = (void __user *)arg;
 164         static const struct watchdog_info info = {
 165                 .options =      WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
 166                                 WDIOF_KEEPALIVEPING,
 167                 .firmware_version = 0,
 168                 .identity = "GE watchdog",
 169         };
 170
 171         switch (cmd) {
 172         case WDIOC_GETSUPPORT:
 173                 if (copy_to_user(argp, &info, sizeof(info)))
 174                         return -EFAULT;
 175                 break;
 176
 177         case WDIOC_GETSTATUS:
 178         case WDIOC_GETBOOTSTATUS:
 179                 if (put_user(wdt_status, (int __user *)argp))
 180                         return -EFAULT;
 181                 wdt_status &= ~WDIOF_KEEPALIVEPING;
 182                 break;
 183
 184         case WDIOC_SETOPTIONS:
 185                 if (get_user(options, (int __user *)argp))
 186                         return -EFAULT;
 187
 188                 if (options & WDIOS_DISABLECARD)
 189                         gef_wdt_handler_disable();
 190
 191                 if (options & WDIOS_ENABLECARD)
 192                         gef_wdt_handler_enable();
 193                 break;
 194
 195         case WDIOC_KEEPALIVE:
 196                 gef_wdt_service();
 197                 wdt_status |= WDIOF_KEEPALIVEPING;
 198                 break;
 199
 200         case WDIOC_SETTIMEOUT:
 201                 if (get_user(timeout, (int __user *)argp))
 202                         return -EFAULT;
 203                 gef_wdt_set_timeout(timeout);
 204                 /* Fall through */
 205
 206         case WDIOC_GETTIMEOUT:
 207                 if (put_user(gef_wdt_timeout, (int __user *)argp))
 208                         return -EFAULT;
 209                 break;
 210
 211         default:
 212                 return -ENOTTY;
 213         }
 214
 215         return 0;
 216 }
 217
 218 static int gef_wdt_open(struct inode *inode, struct file *file)
 219 {
 220         if (test_and_set_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags))
 221                 return -EBUSY;
 222
 223         if (nowayout)
 224                 __module_get(THIS_MODULE);
 225
 226         gef_wdt_handler_enable();
 227
 228         return stream_open(inode, file);
 229 }
 230
 231 static int gef_wdt_release(struct inode *inode, struct file *file)
 232 {
 233         if (expect_close == 42)
 234                 gef_wdt_handler_disable();
 235         else {
 236                 pr_crit("unexpected close, not stopping timer!\n");
 237                 gef_wdt_service();
 238         }
 239         expect_close = 0;
 240
 241         clear_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags);
 242
 243         return 0;
 244 }
 245
 246 static const struct file_operations gef_wdt_fops = {
 247         .owner = THIS_MODULE,
 248         .llseek = no_llseek,
 249         .write = gef_wdt_write,
 250         .unlocked_ioctl = gef_wdt_ioctl,
 251         .open = gef_wdt_open,
 252         .release = gef_wdt_release,
 253 };
 254
 255 static struct miscdevice gef_wdt_miscdev = {
 256         .minor = WATCHDOG_MINOR,
 257         .name = "watchdog",
 258         .fops = &gef_wdt_fops,
 259 };
 260
 261
 262 static int gef_wdt_probe(struct platform_device *dev)
 263 {
 264         int timeout = 10;
 265         u32 freq;
 266
 267         bus_clk = 133; /* in MHz */
 268
 269         freq = fsl_get_sys_freq();
 270         if (freq != -1)
 271                 bus_clk = freq;
 272
 273         /* Map devices registers into memory */
 274         gef_wdt_regs = of_iomap(dev->dev.of_node, 0);
 275         if (gef_wdt_regs == NULL)
 276                 return -ENOMEM;
 277
 278         gef_wdt_set_timeout(timeout);
 279
 280         gef_wdt_handler_disable();      /* in case timer was already running */
 281
 282         return misc_register(&gef_wdt_miscdev);
 283 }
 284
 285 static int gef_wdt_remove(struct platform_device *dev)
 286 {
 287         misc_deregister(&gef_wdt_miscdev);
 288
 289         gef_wdt_handler_disable();
 290
 291         iounmap(gef_wdt_regs);
 292
 293         return 0;
 294 }
 295
 296 static const struct of_device_id gef_wdt_ids[] = {
 297         {
 298                 .compatible = "gef,fpga-wdt",
 299         },
 300         {},
 301 };
 302 MODULE_DEVICE_TABLE(of, gef_wdt_ids);
 303
 304 static struct platform_driver gef_wdt_driver = {
 305         .driver = {
 306                 .name = "gef_wdt",
 307                 .of_match_table = gef_wdt_ids,
 308         },
 309         .probe          = gef_wdt_probe,
 310         .remove         = gef_wdt_remove,
 311 };
 312
 313 static int __init gef_wdt_init(void)
 314 {
 315         pr_info("GE watchdog driver\n");
 316         return platform_driver_register(&gef_wdt_driver);
 317 }
 318
 319 static void __exit gef_wdt_exit(void)
 320 {
 321         platform_driver_unregister(&gef_wdt_driver);
 322 }
 323
 324 module_init(gef_wdt_init);
 325 module_exit(gef_wdt_exit);
 326
 327 MODULE_AUTHOR("Martyn Welch <martyn.welch@ge.com>");
 328 MODULE_DESCRIPTION("GE watchdog driver");
 329 MODULE_LICENSE("GPL");
 330 MODULE_ALIAS("platform:gef_wdt");