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 
ar7_wdt_kick(u32 value)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 
ar7_wdt_prescale(u32 value)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 
ar7_wdt_change(u32 value)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 
ar7_wdt_disable(u32 value)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 
ar7_wdt_update_margin(int new_margin)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 
ar7_wdt_enable_wdt(void)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 
ar7_wdt_disable_wdt(void)150 static void ar7_wdt_disable_wdt(void)
151 {
152 	pr_debug("disabling watchdog timer\n");
153 	ar7_wdt_disable(0);
154 }
155 
ar7_wdt_open(struct inode * inode,struct file * file)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 
ar7_wdt_release(struct inode * inode,struct file * file)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 
ar7_wdt_write(struct file * file,const char * data,size_t len,loff_t * ppos)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 
ar7_wdt_ioctl(struct file * file,unsigned int cmd,unsigned long arg)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 
ar7_wdt_probe(struct platform_device * pdev)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 
ar7_wdt_remove(struct platform_device * pdev)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 
ar7_wdt_shutdown(struct platform_device * pdev)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);
317