drivers/watchdog/ar7_wdt.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * drivers/watchdog/ar7_wdt.c
   4  *
   5  * Copyright (C) 2007 Nicolas Thill <nico@openwrt.org>
   6  * Copyright (c) 2005 Enrik Berkhan <Enrik.Berkhan@akk.org>
   7  *
   8  * Some code taken from:
   9  * National Semiconductor SCx200 Watchdog support
  10  * Copyright (c) 2001,2002 Christer Weinigel <wingel@nano-system.com>
  11  *
  12  */
  13
  14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  15
  16 #include <linux/module.h>
  17 #include <linux/moduleparam.h>
  18 #include <linux/errno.h>
  19 #include <linux/miscdevice.h>
  20 #include <linux/platform_device.h>
  21 #include <linux/watchdog.h>
  22 #include <linux/fs.h>
  23 #include <linux/ioport.h>
  24 #include <linux/io.h>
  25 #include <linux/uaccess.h>
  26 #include <linux/clk.h>
  27
  28 #include <asm/addrspace.h>
  29 #include <asm/mach-ar7/ar7.h>
  30
  31 #define LONGNAME "TI AR7 Watchdog Timer"
  32
  33 MODULE_AUTHOR("Nicolas Thill <nico@openwrt.org>");
  34 MODULE_DESCRIPTION(LONGNAME);
  35 MODULE_LICENSE("GPL");
  36
  37 static int margin = 60;
  38 module_param(margin, int, 0);
  39 MODULE_PARM_DESC(margin, "Watchdog margin in seconds");
  40
  41 static bool nowayout = WATCHDOG_NOWAYOUT;
  42 module_param(nowayout, bool, 0);
  43 MODULE_PARM_DESC(nowayout, "Disable watchdog shutdown on close");
  44
  45 #define READ_REG(x) readl((void __iomem *)&(x))
  46 #define WRITE_REG(x, v) writel((v), (void __iomem *)&(x))
  47
  48 struct ar7_wdt {
  49         u32 kick_lock;
  50         u32 kick;
  51         u32 change_lock;
  52         u32 change;
  53         u32 disable_lock;
  54         u32 disable;
  55         u32 prescale_lock;
  56         u32 prescale;
  57 };
  58
  59 static unsigned long wdt_is_open;
  60 static unsigned expect_close;
  61 static DEFINE_SPINLOCK(wdt_lock);
  62
  63 /* XXX currently fixed, allows max margin ~68.72 secs */
  64 #define prescale_value 0xffff
  65
  66 /* Pointer to the remapped WDT IO space */
  67 static struct ar7_wdt *ar7_wdt;
  68
  69 static struct clk *vbus_clk;
  70
  71 static void ar7_wdt_kick(u32 value)
  72 {
  73         WRITE_REG(ar7_wdt->kick_lock, 0x5555);
  74         if ((READ_REG(ar7_wdt->kick_lock) & 3) == 1) {
  75                 WRITE_REG(ar7_wdt->kick_lock, 0xaaaa);
  76                 if ((READ_REG(ar7_wdt->kick_lock) & 3) == 3) {
  77                         WRITE_REG(ar7_wdt->kick, value);
  78                         return;
  79                 }
  80         }
  81         pr_err("failed to unlock WDT kick reg\n");
  82 }
  83
  84 static void ar7_wdt_prescale(u32 value)
  85 {
  86         WRITE_REG(ar7_wdt->prescale_lock, 0x5a5a);
  87         if ((READ_REG(ar7_wdt->prescale_lock) & 3) == 1) {
  88                 WRITE_REG(ar7_wdt->prescale_lock, 0xa5a5);
  89                 if ((READ_REG(ar7_wdt->prescale_lock) & 3) == 3) {
  90                         WRITE_REG(ar7_wdt->prescale, value);
  91                         return;
  92                 }
  93         }
  94         pr_err("failed to unlock WDT prescale reg\n");
  95 }
  96
  97 static void ar7_wdt_change(u32 value)
  98 {
  99         WRITE_REG(ar7_wdt->change_lock, 0x6666);
 100         if ((READ_REG(ar7_wdt->change_lock) & 3) == 1) {
 101                 WRITE_REG(ar7_wdt->change_lock, 0xbbbb);
 102                 if ((READ_REG(ar7_wdt->change_lock) & 3) == 3) {
 103                         WRITE_REG(ar7_wdt->change, value);
 104                         return;
 105                 }
 106         }
 107         pr_err("failed to unlock WDT change reg\n");
 108 }
 109
 110 static void ar7_wdt_disable(u32 value)
 111 {
 112         WRITE_REG(ar7_wdt->disable_lock, 0x7777);
 113         if ((READ_REG(ar7_wdt->disable_lock) & 3) == 1) {
 114                 WRITE_REG(ar7_wdt->disable_lock, 0xcccc);
 115                 if ((READ_REG(ar7_wdt->disable_lock) & 3) == 2) {
 116                         WRITE_REG(ar7_wdt->disable_lock, 0xdddd);
 117                         if ((READ_REG(ar7_wdt->disable_lock) & 3) == 3) {
 118                                 WRITE_REG(ar7_wdt->disable, value);
 119                                 return;
 120                         }
 121                 }
 122         }
 123         pr_err("failed to unlock WDT disable reg\n");
 124 }
 125
 126 static void ar7_wdt_update_margin(int new_margin)
 127 {
 128         u32 change;
 129         u32 vbus_rate;
 130
 131         vbus_rate = clk_get_rate(vbus_clk);
 132         change = new_margin * (vbus_rate / prescale_value);
 133         if (change < 1)
 134                 change = 1;
 135         if (change > 0xffff)
 136                 change = 0xffff;
 137         ar7_wdt_change(change);
 138         margin = change * prescale_value / vbus_rate;
 139         pr_info("timer margin %d seconds (prescale %d, change %d, freq %d)\n",
 140                 margin, prescale_value, change, vbus_rate);
 141 }
 142
 143 static void ar7_wdt_enable_wdt(void)
 144 {
 145         pr_debug("enabling watchdog timer\n");
 146         ar7_wdt_disable(1);
 147         ar7_wdt_kick(1);
 148 }
 149
 150 static void ar7_wdt_disable_wdt(void)
 151 {
 152         pr_debug("disabling watchdog timer\n");
 153         ar7_wdt_disable(0);
 154 }
 155
 156 static int ar7_wdt_open(struct inode *inode, struct file *file)
 157 {
 158         /* only allow one at a time */
 159         if (test_and_set_bit(0, &wdt_is_open))
 160                 return -EBUSY;
 161         ar7_wdt_enable_wdt();
 162         expect_close = 0;
 163
 164         return stream_open(inode, file);
 165 }
 166
 167 static int ar7_wdt_release(struct inode *inode, struct file *file)
 168 {
 169         if (!expect_close)
 170                 pr_warn("watchdog device closed unexpectedly, will not disable the watchdog timer\n");
 171         else if (!nowayout)
 172                 ar7_wdt_disable_wdt();
 173         clear_bit(0, &wdt_is_open);
 174         return 0;
 175 }
 176
 177 static ssize_t ar7_wdt_write(struct file *file, const char *data,
 178                              size_t len, loff_t *ppos)
 179 {
 180         /* check for a magic close character */
 181         if (len) {
 182                 size_t i;
 183
 184                 spin_lock(&wdt_lock);
 185                 ar7_wdt_kick(1);
 186                 spin_unlock(&wdt_lock);
 187
 188                 expect_close = 0;
 189                 for (i = 0; i < len; ++i) {
 190                         char c;
 191                         if (get_user(c, data + i))
 192                                 return -EFAULT;
 193                         if (c == 'V')
 194                                 expect_close = 1;
 195                 }
 196
 197         }
 198         return len;
 199 }
 200
 201 static long ar7_wdt_ioctl(struct file *file,
 202                                         unsigned int cmd, unsigned long arg)
 203 {
 204         static const struct watchdog_info ident = {
 205                 .identity = LONGNAME,
 206                 .firmware_version = 1,
 207                 .options = (WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
 208                                                 WDIOF_MAGICCLOSE),
 209         };
 210         int new_margin;
 211
 212         switch (cmd) {
 213         case WDIOC_GETSUPPORT:
 214                 if (copy_to_user((struct watchdog_info *)arg, &ident,
 215                                 sizeof(ident)))
 216                         return -EFAULT;
 217                 return 0;
 218         case WDIOC_GETSTATUS:
 219         case WDIOC_GETBOOTSTATUS:
 220                 if (put_user(0, (int *)arg))
 221                         return -EFAULT;
 222                 return 0;
 223         case WDIOC_KEEPALIVE:
 224                 ar7_wdt_kick(1);
 225                 return 0;
 226         case WDIOC_SETTIMEOUT:
 227                 if (get_user(new_margin, (int *)arg))
 228                         return -EFAULT;
 229                 if (new_margin < 1)
 230                         return -EINVAL;
 231
 232                 spin_lock(&wdt_lock);
 233                 ar7_wdt_update_margin(new_margin);
 234                 ar7_wdt_kick(1);
 235                 spin_unlock(&wdt_lock);
 236                 fallthrough;
 237         case WDIOC_GETTIMEOUT:
 238                 if (put_user(margin, (int *)arg))
 239                         return -EFAULT;
 240                 return 0;
 241         default:
 242                 return -ENOTTY;
 243         }
 244 }
 245
 246 static const struct file_operations ar7_wdt_fops = {
 247         .owner          = THIS_MODULE,
 248         .write          = ar7_wdt_write,
 249         .unlocked_ioctl = ar7_wdt_ioctl,
 250         .compat_ioctl   = compat_ptr_ioctl,
 251         .open           = ar7_wdt_open,
 252         .release        = ar7_wdt_release,
 253         .llseek         = no_llseek,
 254 };
 255
 256 static struct miscdevice ar7_wdt_miscdev = {
 257         .minor          = WATCHDOG_MINOR,
 258         .name           = "watchdog",
 259         .fops           = &ar7_wdt_fops,
 260 };
 261
 262 static int ar7_wdt_probe(struct platform_device *pdev)
 263 {
 264         int rc;
 265
 266         ar7_wdt = devm_platform_ioremap_resource_byname(pdev, "regs");
 267         if (IS_ERR(ar7_wdt))
 268                 return PTR_ERR(ar7_wdt);
 269
 270         vbus_clk = clk_get(NULL, "vbus");
 271         if (IS_ERR(vbus_clk)) {
 272                 pr_err("could not get vbus clock\n");
 273                 return PTR_ERR(vbus_clk);
 274         }
 275
 276         ar7_wdt_disable_wdt();
 277         ar7_wdt_prescale(prescale_value);
 278         ar7_wdt_update_margin(margin);
 279
 280         rc = misc_register(&ar7_wdt_miscdev);
 281         if (rc) {
 282                 pr_err("unable to register misc device\n");
 283                 goto out;
 284         }
 285         return 0;
 286
 287 out:
 288         clk_put(vbus_clk);
 289         vbus_clk = NULL;
 290         return rc;
 291 }
 292
 293 static int ar7_wdt_remove(struct platform_device *pdev)
 294 {
 295         misc_deregister(&ar7_wdt_miscdev);
 296         clk_put(vbus_clk);
 297         vbus_clk = NULL;
 298         return 0;
 299 }
 300
 301 static void ar7_wdt_shutdown(struct platform_device *pdev)
 302 {
 303         if (!nowayout)
 304                 ar7_wdt_disable_wdt();
 305 }
 306
 307 static struct platform_driver ar7_wdt_driver = {
 308         .probe = ar7_wdt_probe,
 309         .remove = ar7_wdt_remove,
 310         .shutdown = ar7_wdt_shutdown,
 311         .driver = {
 312                 .name = "ar7_wdt",
 313         },
 314 };
 315
 316 module_platform_driver(ar7_wdt_driver);