drivers/watchdog/lantiq_wdt.c

   1 /*
   2  *  This program is free software; you can redistribute it and/or modify it
   3  *  under the terms of the GNU General Public License version 2 as published
   4  *  by the Free Software Foundation.
   5  *
   6  *  Copyright (C) 2010 John Crispin <blogic@openwrt.org>
   7  *  Based on EP93xx wdt driver
   8  */
   9
  10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  11
  12 #include <linux/module.h>
  13 #include <linux/fs.h>
  14 #include <linux/miscdevice.h>
  15 #include <linux/watchdog.h>
  16 #include <linux/of_platform.h>
  17 #include <linux/uaccess.h>
  18 #include <linux/clk.h>
  19 #include <linux/io.h>
  20
  21 #include <lantiq_soc.h>
  22
  23 /*
  24  * Section 3.4 of the datasheet
  25  * The password sequence protects the WDT control register from unintended
  26  * write actions, which might cause malfunction of the WDT.
  27  *
  28  * essentially the following two magic passwords need to be written to allow
  29  * IO access to the WDT core
  30  */
  31 #define LTQ_WDT_PW1             0x00BE0000
  32 #define LTQ_WDT_PW2             0x00DC0000
  33
  34 #define LTQ_WDT_CR              0x0     /* watchdog control register */
  35 #define LTQ_WDT_SR              0x8     /* watchdog status register */
  36
  37 #define LTQ_WDT_SR_EN           (0x1 << 31)     /* enable bit */
  38 #define LTQ_WDT_SR_PWD          (0x3 << 26)     /* turn on power */
  39 #define LTQ_WDT_SR_CLKDIV       (0x3 << 24)     /* turn on clock and set */
  40                                                 /* divider to 0x40000 */
  41 #define LTQ_WDT_DIVIDER         0x40000
  42 #define LTQ_MAX_TIMEOUT         ((1 << 16) - 1) /* the reload field is 16 bit */
  43
  44 static bool nowayout = WATCHDOG_NOWAYOUT;
  45
  46 static void __iomem *ltq_wdt_membase;
  47 static unsigned long ltq_io_region_clk_rate;
  48
  49 static unsigned long ltq_wdt_bootstatus;
  50 static unsigned long ltq_wdt_in_use;
  51 static int ltq_wdt_timeout = 30;
  52 static int ltq_wdt_ok_to_close;
  53
  54 static void
  55 ltq_wdt_enable(void)
  56 {
  57         unsigned long int timeout = ltq_wdt_timeout *
  58                         (ltq_io_region_clk_rate / LTQ_WDT_DIVIDER) + 0x1000;
  59         if (timeout > LTQ_MAX_TIMEOUT)
  60                 timeout = LTQ_MAX_TIMEOUT;
  61
  62         /* write the first password magic */
  63         ltq_w32(LTQ_WDT_PW1, ltq_wdt_membase + LTQ_WDT_CR);
  64         /* write the second magic plus the configuration and new timeout */
  65         ltq_w32(LTQ_WDT_SR_EN | LTQ_WDT_SR_PWD | LTQ_WDT_SR_CLKDIV |
  66                 LTQ_WDT_PW2 | timeout, ltq_wdt_membase + LTQ_WDT_CR);
  67 }
  68
  69 static void
  70 ltq_wdt_disable(void)
  71 {
  72         /* write the first password magic */
  73         ltq_w32(LTQ_WDT_PW1, ltq_wdt_membase + LTQ_WDT_CR);
  74         /*
  75          * write the second password magic with no config
  76          * this turns the watchdog off
  77          */
  78         ltq_w32(LTQ_WDT_PW2, ltq_wdt_membase + LTQ_WDT_CR);
  79 }
  80
  81 static ssize_t
  82 ltq_wdt_write(struct file *file, const char __user *data,
  83                 size_t len, loff_t *ppos)
  84 {
  85         if (len) {
  86                 if (!nowayout) {
  87                         size_t i;
  88
  89                         ltq_wdt_ok_to_close = 0;
  90                         for (i = 0; i != len; i++) {
  91                                 char c;
  92
  93                                 if (get_user(c, data + i))
  94                                         return -EFAULT;
  95                                 if (c == 'V')
  96                                         ltq_wdt_ok_to_close = 1;
  97                                 else
  98                                         ltq_wdt_ok_to_close = 0;
  99                         }
 100                 }
 101                 ltq_wdt_enable();
 102         }
 103
 104         return len;
 105 }
 106
 107 static struct watchdog_info ident = {
 108         .options = WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
 109                         WDIOF_CARDRESET,
 110         .identity = "ltq_wdt",
 111 };
 112
 113 static long
 114 ltq_wdt_ioctl(struct file *file,
 115                 unsigned int cmd, unsigned long arg)
 116 {
 117         int ret = -ENOTTY;
 118
 119         switch (cmd) {
 120         case WDIOC_GETSUPPORT:
 121                 ret = copy_to_user((struct watchdog_info __user *)arg, &ident,
 122                                 sizeof(ident)) ? -EFAULT : 0;
 123                 break;
 124
 125         case WDIOC_GETBOOTSTATUS:
 126                 ret = put_user(ltq_wdt_bootstatus, (int __user *)arg);
 127                 break;
 128
 129         case WDIOC_GETSTATUS:
 130                 ret = put_user(0, (int __user *)arg);
 131                 break;
 132
 133         case WDIOC_SETTIMEOUT:
 134                 ret = get_user(ltq_wdt_timeout, (int __user *)arg);
 135                 if (!ret)
 136                         ltq_wdt_enable();
 137                 /* intentional drop through */
 138         case WDIOC_GETTIMEOUT:
 139                 ret = put_user(ltq_wdt_timeout, (int __user *)arg);
 140                 break;
 141
 142         case WDIOC_KEEPALIVE:
 143                 ltq_wdt_enable();
 144                 ret = 0;
 145                 break;
 146         }
 147         return ret;
 148 }
 149
 150 static int
 151 ltq_wdt_open(struct inode *inode, struct file *file)
 152 {
 153         if (test_and_set_bit(0, &ltq_wdt_in_use))
 154                 return -EBUSY;
 155         ltq_wdt_in_use = 1;
 156         ltq_wdt_enable();
 157
 158         return nonseekable_open(inode, file);
 159 }
 160
 161 static int
 162 ltq_wdt_release(struct inode *inode, struct file *file)
 163 {
 164         if (ltq_wdt_ok_to_close)
 165                 ltq_wdt_disable();
 166         else
 167                 pr_err("watchdog closed without warning\n");
 168         ltq_wdt_ok_to_close = 0;
 169         clear_bit(0, &ltq_wdt_in_use);
 170
 171         return 0;
 172 }
 173
 174 static const struct file_operations ltq_wdt_fops = {
 175         .owner          = THIS_MODULE,
 176         .write          = ltq_wdt_write,
 177         .unlocked_ioctl = ltq_wdt_ioctl,
 178         .open           = ltq_wdt_open,
 179         .release        = ltq_wdt_release,
 180         .llseek         = no_llseek,
 181 };
 182
 183 static struct miscdevice ltq_wdt_miscdev = {
 184         .minor  = WATCHDOG_MINOR,
 185         .name   = "watchdog",
 186         .fops   = &ltq_wdt_fops,
 187 };
 188
 189 static int
 190 ltq_wdt_probe(struct platform_device *pdev)
 191 {
 192         struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 193         struct clk *clk;
 194
 195         ltq_wdt_membase = devm_ioremap_resource(&pdev->dev, res);
 196         if (IS_ERR(ltq_wdt_membase))
 197                 return PTR_ERR(ltq_wdt_membase);
 198
 199         /* we do not need to enable the clock as it is always running */
 200         clk = clk_get_io();
 201         if (IS_ERR(clk)) {
 202                 dev_err(&pdev->dev, "Failed to get clock\n");
 203                 return -ENOENT;
 204         }
 205         ltq_io_region_clk_rate = clk_get_rate(clk);
 206         clk_put(clk);
 207
 208         /* find out if the watchdog caused the last reboot */
 209         if (ltq_reset_cause() == LTQ_RST_CAUSE_WDTRST)
 210                 ltq_wdt_bootstatus = WDIOF_CARDRESET;
 211
 212         dev_info(&pdev->dev, "Init done\n");
 213         return misc_register(&ltq_wdt_miscdev);
 214 }
 215
 216 static int
 217 ltq_wdt_remove(struct platform_device *pdev)
 218 {
 219         misc_deregister(&ltq_wdt_miscdev);
 220
 221         return 0;
 222 }
 223
 224 static const struct of_device_id ltq_wdt_match[] = {
 225         { .compatible = "lantiq,wdt" },
 226         {},
 227 };
 228 MODULE_DEVICE_TABLE(of, ltq_wdt_match);
 229
 230 static struct platform_driver ltq_wdt_driver = {
 231         .probe = ltq_wdt_probe,
 232         .remove = ltq_wdt_remove,
 233         .driver = {
 234                 .name = "wdt",
 235                 .of_match_table = ltq_wdt_match,
 236         },
 237 };
 238
 239 module_platform_driver(ltq_wdt_driver);
 240
 241 module_param(nowayout, bool, 0);
 242 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started");
 243 MODULE_AUTHOR("John Crispin <blogic@openwrt.org>");
 244 MODULE_DESCRIPTION("Lantiq SoC Watchdog");
 245 MODULE_LICENSE("GPL");