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Linux/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         if (!res) {
196                 dev_err(&pdev->dev, "cannot obtain I/O memory region");
197                 return -ENOENT;
198         }
199 
200         ltq_wdt_membase = devm_ioremap_resource(&pdev->dev, res);
201         if (IS_ERR(ltq_wdt_membase))
202                 return PTR_ERR(ltq_wdt_membase);
203 
204         /* we do not need to enable the clock as it is always running */
205         clk = clk_get_io();
206         if (IS_ERR(clk)) {
207                 dev_err(&pdev->dev, "Failed to get clock\n");
208                 return -ENOENT;
209         }
210         ltq_io_region_clk_rate = clk_get_rate(clk);
211         clk_put(clk);
212 
213         /* find out if the watchdog caused the last reboot */
214         if (ltq_reset_cause() == LTQ_RST_CAUSE_WDTRST)
215                 ltq_wdt_bootstatus = WDIOF_CARDRESET;
216 
217         dev_info(&pdev->dev, "Init done\n");
218         return misc_register(&ltq_wdt_miscdev);
219 }
220 
221 static int
222 ltq_wdt_remove(struct platform_device *pdev)
223 {
224         misc_deregister(&ltq_wdt_miscdev);
225 
226         return 0;
227 }
228 
229 static const struct of_device_id ltq_wdt_match[] = {
230         { .compatible = "lantiq,wdt" },
231         {},
232 };
233 MODULE_DEVICE_TABLE(of, ltq_wdt_match);
234 
235 static struct platform_driver ltq_wdt_driver = {
236         .probe = ltq_wdt_probe,
237         .remove = ltq_wdt_remove,
238         .driver = {
239                 .name = "wdt",
240                 .owner = THIS_MODULE,
241                 .of_match_table = ltq_wdt_match,
242         },
243 };
244 
245 module_platform_driver(ltq_wdt_driver);
246 
247 module_param(nowayout, bool, 0);
248 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started");
249 MODULE_AUTHOR("John Crispin <blogic@openwrt.org>");
250 MODULE_DESCRIPTION("Lantiq SoC Watchdog");
251 MODULE_LICENSE("GPL");
252 

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