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/platform_device.h>
17 #include <linux/uaccess.h>
18 #include <linux/clk.h>
19 #include <linux/io.h>
20 
21 #include <lantiq.h>
22 
23 /* Section 3.4 of the datasheet
24  * The password sequence protects the WDT control register from unintended
25  * write actions, which might cause malfunction of the WDT.
26  *
27  * essentially the following two magic passwords need to be written to allow
28  * IO access to the WDT core
29  */
30 #define LTQ_WDT_PW1		0x00BE0000
31 #define LTQ_WDT_PW2		0x00DC0000
32 
33 #define LTQ_WDT_CR		0x0	/* watchdog control register */
34 #define LTQ_WDT_SR		0x8	/* watchdog status register */
35 
36 #define LTQ_WDT_SR_EN		(0x1 << 31)	/* enable bit */
37 #define LTQ_WDT_SR_PWD		(0x3 << 26)	/* turn on power */
38 #define LTQ_WDT_SR_CLKDIV	(0x3 << 24)	/* turn on clock and set */
39 						/* divider to 0x40000 */
40 #define LTQ_WDT_DIVIDER		0x40000
41 #define LTQ_MAX_TIMEOUT		((1 << 16) - 1)	/* the reload field is 16 bit */
42 
43 static bool nowayout = WATCHDOG_NOWAYOUT;
44 
45 static void __iomem *ltq_wdt_membase;
46 static unsigned long ltq_io_region_clk_rate;
47 
48 static unsigned long ltq_wdt_bootstatus;
49 static unsigned long ltq_wdt_in_use;
50 static int ltq_wdt_timeout = 30;
51 static int ltq_wdt_ok_to_close;
52 
53 static void
ltq_wdt_enable(void)54 ltq_wdt_enable(void)
55 {
56 	unsigned long int timeout = ltq_wdt_timeout *
57 			(ltq_io_region_clk_rate / LTQ_WDT_DIVIDER) + 0x1000;
58 	if (timeout > LTQ_MAX_TIMEOUT)
59 		timeout = LTQ_MAX_TIMEOUT;
60 
61 	/* write the first password magic */
62 	ltq_w32(LTQ_WDT_PW1, ltq_wdt_membase + LTQ_WDT_CR);
63 	/* write the second magic plus the configuration and new timeout */
64 	ltq_w32(LTQ_WDT_SR_EN | LTQ_WDT_SR_PWD | LTQ_WDT_SR_CLKDIV |
65 		LTQ_WDT_PW2 | timeout, ltq_wdt_membase + LTQ_WDT_CR);
66 }
67 
68 static void
ltq_wdt_disable(void)69 ltq_wdt_disable(void)
70 {
71 	/* write the first password magic */
72 	ltq_w32(LTQ_WDT_PW1, ltq_wdt_membase + LTQ_WDT_CR);
73 	/* write the second password magic with no config
74 	 * this turns the watchdog off
75 	 */
76 	ltq_w32(LTQ_WDT_PW2, ltq_wdt_membase + LTQ_WDT_CR);
77 }
78 
79 static ssize_t
ltq_wdt_write(struct file * file,const char __user * data,size_t len,loff_t * ppos)80 ltq_wdt_write(struct file *file, const char __user *data,
81 		size_t len, loff_t *ppos)
82 {
83 	if (len) {
84 		if (!nowayout) {
85 			size_t i;
86 
87 			ltq_wdt_ok_to_close = 0;
88 			for (i = 0; i != len; i++) {
89 				char c;
90 
91 				if (get_user(c, data + i))
92 					return -EFAULT;
93 				if (c == 'V')
94 					ltq_wdt_ok_to_close = 1;
95 				else
96 					ltq_wdt_ok_to_close = 0;
97 			}
98 		}
99 		ltq_wdt_enable();
100 	}
101 
102 	return len;
103 }
104 
105 static struct watchdog_info ident = {
106 	.options = WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
107 			WDIOF_CARDRESET,
108 	.identity = "ltq_wdt",
109 };
110 
111 static long
ltq_wdt_ioctl(struct file * file,unsigned int cmd,unsigned long arg)112 ltq_wdt_ioctl(struct file *file,
113 		unsigned int cmd, unsigned long arg)
114 {
115 	int ret = -ENOTTY;
116 
117 	switch (cmd) {
118 	case WDIOC_GETSUPPORT:
119 		ret = copy_to_user((struct watchdog_info __user *)arg, &ident,
120 				sizeof(ident)) ? -EFAULT : 0;
121 		break;
122 
123 	case WDIOC_GETBOOTSTATUS:
124 		ret = put_user(ltq_wdt_bootstatus, (int __user *)arg);
125 		break;
126 
127 	case WDIOC_GETSTATUS:
128 		ret = put_user(0, (int __user *)arg);
129 		break;
130 
131 	case WDIOC_SETTIMEOUT:
132 		ret = get_user(ltq_wdt_timeout, (int __user *)arg);
133 		if (!ret)
134 			ltq_wdt_enable();
135 		/* intentional drop through */
136 	case WDIOC_GETTIMEOUT:
137 		ret = put_user(ltq_wdt_timeout, (int __user *)arg);
138 		break;
139 
140 	case WDIOC_KEEPALIVE:
141 		ltq_wdt_enable();
142 		ret = 0;
143 		break;
144 	}
145 	return ret;
146 }
147 
148 static int
ltq_wdt_open(struct inode * inode,struct file * file)149 ltq_wdt_open(struct inode *inode, struct file *file)
150 {
151 	if (test_and_set_bit(0, &ltq_wdt_in_use))
152 		return -EBUSY;
153 	ltq_wdt_in_use = 1;
154 	ltq_wdt_enable();
155 
156 	return nonseekable_open(inode, file);
157 }
158 
159 static int
ltq_wdt_release(struct inode * inode,struct file * file)160 ltq_wdt_release(struct inode *inode, struct file *file)
161 {
162 	if (ltq_wdt_ok_to_close)
163 		ltq_wdt_disable();
164 	else
165 		pr_err("watchdog closed without warning\n");
166 	ltq_wdt_ok_to_close = 0;
167 	clear_bit(0, &ltq_wdt_in_use);
168 
169 	return 0;
170 }
171 
172 static const struct file_operations ltq_wdt_fops = {
173 	.owner		= THIS_MODULE,
174 	.write		= ltq_wdt_write,
175 	.unlocked_ioctl	= ltq_wdt_ioctl,
176 	.open		= ltq_wdt_open,
177 	.release	= ltq_wdt_release,
178 	.llseek		= no_llseek,
179 };
180 
181 static struct miscdevice ltq_wdt_miscdev = {
182 	.minor	= WATCHDOG_MINOR,
183 	.name	= "watchdog",
184 	.fops	= &ltq_wdt_fops,
185 };
186 
187 static int __init
ltq_wdt_probe(struct platform_device * pdev)188 ltq_wdt_probe(struct platform_device *pdev)
189 {
190 	struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
191 	struct clk *clk;
192 
193 	if (!res) {
194 		dev_err(&pdev->dev, "cannot obtain I/O memory region");
195 		return -ENOENT;
196 	}
197 	res = devm_request_mem_region(&pdev->dev, res->start,
198 		resource_size(res), dev_name(&pdev->dev));
199 	if (!res) {
200 		dev_err(&pdev->dev, "cannot request I/O memory region");
201 		return -EBUSY;
202 	}
203 	ltq_wdt_membase = devm_ioremap_nocache(&pdev->dev, res->start,
204 		resource_size(res));
205 	if (!ltq_wdt_membase) {
206 		dev_err(&pdev->dev, "cannot remap I/O memory region\n");
207 		return -ENOMEM;
208 	}
209 
210 	/* we do not need to enable the clock as it is always running */
211 	clk = clk_get(&pdev->dev, "io");
212 	WARN_ON(!clk);
213 	ltq_io_region_clk_rate = clk_get_rate(clk);
214 	clk_put(clk);
215 
216 	if (ltq_reset_cause() == LTQ_RST_CAUSE_WDTRST)
217 		ltq_wdt_bootstatus = WDIOF_CARDRESET;
218 
219 	return misc_register(&ltq_wdt_miscdev);
220 }
221 
222 static int __devexit
ltq_wdt_remove(struct platform_device * pdev)223 ltq_wdt_remove(struct platform_device *pdev)
224 {
225 	misc_deregister(&ltq_wdt_miscdev);
226 
227 	return 0;
228 }
229 
230 
231 static struct platform_driver ltq_wdt_driver = {
232 	.remove = __devexit_p(ltq_wdt_remove),
233 	.driver = {
234 		.name = "ltq_wdt",
235 		.owner = THIS_MODULE,
236 	},
237 };
238 
239 static int __init
init_ltq_wdt(void)240 init_ltq_wdt(void)
241 {
242 	return platform_driver_probe(&ltq_wdt_driver, ltq_wdt_probe);
243 }
244 
245 static void __exit
exit_ltq_wdt(void)246 exit_ltq_wdt(void)
247 {
248 	return platform_driver_unregister(&ltq_wdt_driver);
249 }
250 
251 module_init(init_ltq_wdt);
252 module_exit(exit_ltq_wdt);
253 
254 module_param(nowayout, bool, 0);
255 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started");
256 
257 MODULE_AUTHOR("John Crispin <blogic@openwrt.org>");
258 MODULE_DESCRIPTION("Lantiq SoC Watchdog");
259 MODULE_LICENSE("GPL");
260 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
261