xref: /linux/drivers/watchdog/gef_wdt.c (revision 93df8a1ed6231727c5db94a80b1a6bd5ee67cec3) 
1 /*
2  * GE watchdog userspace interface
3  *
4  * Author:  Martyn Welch <martyn.welch@ge.com>
5  *
6  * Copyright 2008 GE Intelligent Platforms Embedded Systems, Inc.
7  *
8  * This program is free software; you can redistribute  it and/or modify it
9  * under  the terms of  the GNU General  Public License as published by the
10  * Free Software Foundation;  either version 2 of the  License, or (at your
11  * option) any later version.
12  *
13  * Based on: mv64x60_wdt.c (MV64X60 watchdog userspace interface)
14  *   Author: James Chapman <jchapman@katalix.com>
15  */
16 
17 /* TODO:
18  * This driver does not provide support for the hardwares capability of sending
19  * an interrupt at a programmable threshold.
20  *
21  * This driver currently can only support 1 watchdog - there are 2 in the
22  * hardware that this driver supports. Thus one could be configured as a
23  * process-based watchdog (via /dev/watchdog), the second (using the interrupt
24  * capabilities) a kernel-based watchdog.
25  */
26 
27 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
28 
29 #include <linux/kernel.h>
30 #include <linux/compiler.h>
31 #include <linux/init.h>
32 #include <linux/module.h>
33 #include <linux/miscdevice.h>
34 #include <linux/watchdog.h>
35 #include <linux/fs.h>
36 #include <linux/of.h>
37 #include <linux/of_address.h>
38 #include <linux/of_platform.h>
39 #include <linux/io.h>
40 #include <linux/uaccess.h>
41 
42 #include <sysdev/fsl_soc.h>
43 
44 /*
45  * The watchdog configuration register contains a pair of 2-bit fields,
46  *   1.  a reload field, bits 27-26, which triggers a reload of
47  *       the countdown register, and
48  *   2.  an enable field, bits 25-24, which toggles between
49  *       enabling and disabling the watchdog timer.
50  * Bit 31 is a read-only field which indicates whether the
51  * watchdog timer is currently enabled.
52  *
53  * The low 24 bits contain the timer reload value.
54  */
55 #define GEF_WDC_ENABLE_SHIFT	24
56 #define GEF_WDC_SERVICE_SHIFT	26
57 #define GEF_WDC_ENABLED_SHIFT	31
58 
59 #define GEF_WDC_ENABLED_TRUE	1
60 #define GEF_WDC_ENABLED_FALSE	0
61 
62 /* Flags bits */
63 #define GEF_WDOG_FLAG_OPENED	0
64 
65 static unsigned long wdt_flags;
66 static int wdt_status;
67 static void __iomem *gef_wdt_regs;
68 static int gef_wdt_timeout;
69 static int gef_wdt_count;
70 static unsigned int bus_clk;
71 static char expect_close;
72 static DEFINE_SPINLOCK(gef_wdt_spinlock);
73 
74 static bool nowayout = WATCHDOG_NOWAYOUT;
75 module_param(nowayout, bool, 0);
76 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
77 	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
78 
79 
80 static int gef_wdt_toggle_wdc(int enabled_predicate, int field_shift)
81 {
82 	u32 data;
83 	u32 enabled;
84 	int ret = 0;
85 
86 	spin_lock(&gef_wdt_spinlock);
87 	data = ioread32be(gef_wdt_regs);
88 	enabled = (data >> GEF_WDC_ENABLED_SHIFT) & 1;
89 
90 	/* only toggle the requested field if enabled state matches predicate */
91 	if ((enabled ^ enabled_predicate) == 0) {
92 		/* We write a 1, then a 2 -- to the appropriate field */
93 		data = (1 << field_shift) | gef_wdt_count;
94 		iowrite32be(data, gef_wdt_regs);
95 
96 		data = (2 << field_shift) | gef_wdt_count;
97 		iowrite32be(data, gef_wdt_regs);
98 		ret = 1;
99 	}
100 	spin_unlock(&gef_wdt_spinlock);
101 
102 	return ret;
103 }
104 
105 static void gef_wdt_service(void)
106 {
107 	gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
108 		GEF_WDC_SERVICE_SHIFT);
109 }
110 
111 static void gef_wdt_handler_enable(void)
112 {
113 	if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_FALSE,
114 				   GEF_WDC_ENABLE_SHIFT)) {
115 		gef_wdt_service();
116 		pr_notice("watchdog activated\n");
117 	}
118 }
119 
120 static void gef_wdt_handler_disable(void)
121 {
122 	if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
123 				   GEF_WDC_ENABLE_SHIFT))
124 		pr_notice("watchdog deactivated\n");
125 }
126 
127 static void gef_wdt_set_timeout(unsigned int timeout)
128 {
129 	/* maximum bus cycle count is 0xFFFFFFFF */
130 	if (timeout > 0xFFFFFFFF / bus_clk)
131 		timeout = 0xFFFFFFFF / bus_clk;
132 
133 	/* Register only holds upper 24 bits, bit shifted into lower 24 */
134 	gef_wdt_count = (timeout * bus_clk) >> 8;
135 	gef_wdt_timeout = timeout;
136 }
137 
138 
139 static ssize_t gef_wdt_write(struct file *file, const char __user *data,
140 				 size_t len, loff_t *ppos)
141 {
142 	if (len) {
143 		if (!nowayout) {
144 			size_t i;
145 
146 			expect_close = 0;
147 
148 			for (i = 0; i != len; i++) {
149 				char c;
150 				if (get_user(c, data + i))
151 					return -EFAULT;
152 				if (c == 'V')
153 					expect_close = 42;
154 			}
155 		}
156 		gef_wdt_service();
157 	}
158 
159 	return len;
160 }
161 
162 static long gef_wdt_ioctl(struct file *file, unsigned int cmd,
163 							unsigned long arg)
164 {
165 	int timeout;
166 	int options;
167 	void __user *argp = (void __user *)arg;
168 	static const struct watchdog_info info = {
169 		.options =	WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
170 				WDIOF_KEEPALIVEPING,
171 		.firmware_version = 0,
172 		.identity = "GE watchdog",
173 	};
174 
175 	switch (cmd) {
176 	case WDIOC_GETSUPPORT:
177 		if (copy_to_user(argp, &info, sizeof(info)))
178 			return -EFAULT;
179 		break;
180 
181 	case WDIOC_GETSTATUS:
182 	case WDIOC_GETBOOTSTATUS:
183 		if (put_user(wdt_status, (int __user *)argp))
184 			return -EFAULT;
185 		wdt_status &= ~WDIOF_KEEPALIVEPING;
186 		break;
187 
188 	case WDIOC_SETOPTIONS:
189 		if (get_user(options, (int __user *)argp))
190 			return -EFAULT;
191 
192 		if (options & WDIOS_DISABLECARD)
193 			gef_wdt_handler_disable();
194 
195 		if (options & WDIOS_ENABLECARD)
196 			gef_wdt_handler_enable();
197 		break;
198 
199 	case WDIOC_KEEPALIVE:
200 		gef_wdt_service();
201 		wdt_status |= WDIOF_KEEPALIVEPING;
202 		break;
203 
204 	case WDIOC_SETTIMEOUT:
205 		if (get_user(timeout, (int __user *)argp))
206 			return -EFAULT;
207 		gef_wdt_set_timeout(timeout);
208 		/* Fall through */
209 
210 	case WDIOC_GETTIMEOUT:
211 		if (put_user(gef_wdt_timeout, (int __user *)argp))
212 			return -EFAULT;
213 		break;
214 
215 	default:
216 		return -ENOTTY;
217 	}
218 
219 	return 0;
220 }
221 
222 static int gef_wdt_open(struct inode *inode, struct file *file)
223 {
224 	if (test_and_set_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags))
225 		return -EBUSY;
226 
227 	if (nowayout)
228 		__module_get(THIS_MODULE);
229 
230 	gef_wdt_handler_enable();
231 
232 	return nonseekable_open(inode, file);
233 }
234 
235 static int gef_wdt_release(struct inode *inode, struct file *file)
236 {
237 	if (expect_close == 42)
238 		gef_wdt_handler_disable();
239 	else {
240 		pr_crit("unexpected close, not stopping timer!\n");
241 		gef_wdt_service();
242 	}
243 	expect_close = 0;
244 
245 	clear_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags);
246 
247 	return 0;
248 }
249 
250 static const struct file_operations gef_wdt_fops = {
251 	.owner = THIS_MODULE,
252 	.llseek = no_llseek,
253 	.write = gef_wdt_write,
254 	.unlocked_ioctl = gef_wdt_ioctl,
255 	.open = gef_wdt_open,
256 	.release = gef_wdt_release,
257 };
258 
259 static struct miscdevice gef_wdt_miscdev = {
260 	.minor = WATCHDOG_MINOR,
261 	.name = "watchdog",
262 	.fops = &gef_wdt_fops,
263 };
264 
265 
266 static int gef_wdt_probe(struct platform_device *dev)
267 {
268 	int timeout = 10;
269 	u32 freq;
270 
271 	bus_clk = 133; /* in MHz */
272 
273 	freq = fsl_get_sys_freq();
274 	if (freq != -1)
275 		bus_clk = freq;
276 
277 	/* Map devices registers into memory */
278 	gef_wdt_regs = of_iomap(dev->dev.of_node, 0);
279 	if (gef_wdt_regs == NULL)
280 		return -ENOMEM;
281 
282 	gef_wdt_set_timeout(timeout);
283 
284 	gef_wdt_handler_disable();	/* in case timer was already running */
285 
286 	return misc_register(&gef_wdt_miscdev);
287 }
288 
289 static int gef_wdt_remove(struct platform_device *dev)
290 {
291 	misc_deregister(&gef_wdt_miscdev);
292 
293 	gef_wdt_handler_disable();
294 
295 	iounmap(gef_wdt_regs);
296 
297 	return 0;
298 }
299 
300 static const struct of_device_id gef_wdt_ids[] = {
301 	{
302 		.compatible = "gef,fpga-wdt",
303 	},
304 	{},
305 };
306 
307 static struct platform_driver gef_wdt_driver = {
308 	.driver = {
309 		.name = "gef_wdt",
310 		.of_match_table = gef_wdt_ids,
311 	},
312 	.probe		= gef_wdt_probe,
313 	.remove		= gef_wdt_remove,
314 };
315 
316 static int __init gef_wdt_init(void)
317 {
318 	pr_info("GE watchdog driver\n");
319 	return platform_driver_register(&gef_wdt_driver);
320 }
321 
322 static void __exit gef_wdt_exit(void)
323 {
324 	platform_driver_unregister(&gef_wdt_driver);
325 }
326 
327 module_init(gef_wdt_init);
328 module_exit(gef_wdt_exit);
329 
330 MODULE_AUTHOR("Martyn Welch <martyn.welch@ge.com>");
331 MODULE_DESCRIPTION("GE watchdog driver");
332 MODULE_LICENSE("GPL");
333 MODULE_ALIAS("platform:gef_wdt");
334