xref: /openbmc/linux/drivers/watchdog/gef_wdt.c (revision d0b73b48) 
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_platform.h>
38 #include <linux/io.h>
39 #include <linux/uaccess.h>
40 
41 #include <sysdev/fsl_soc.h>
42 
43 /*
44  * The watchdog configuration register contains a pair of 2-bit fields,
45  *   1.  a reload field, bits 27-26, which triggers a reload of
46  *       the countdown register, and
47  *   2.  an enable field, bits 25-24, which toggles between
48  *       enabling and disabling the watchdog timer.
49  * Bit 31 is a read-only field which indicates whether the
50  * watchdog timer is currently enabled.
51  *
52  * The low 24 bits contain the timer reload value.
53  */
54 #define GEF_WDC_ENABLE_SHIFT	24
55 #define GEF_WDC_SERVICE_SHIFT	26
56 #define GEF_WDC_ENABLED_SHIFT	31
57 
58 #define GEF_WDC_ENABLED_TRUE	1
59 #define GEF_WDC_ENABLED_FALSE	0
60 
61 /* Flags bits */
62 #define GEF_WDOG_FLAG_OPENED	0
63 
64 static unsigned long wdt_flags;
65 static int wdt_status;
66 static void __iomem *gef_wdt_regs;
67 static int gef_wdt_timeout;
68 static int gef_wdt_count;
69 static unsigned int bus_clk;
70 static char expect_close;
71 static DEFINE_SPINLOCK(gef_wdt_spinlock);
72 
73 static bool nowayout = WATCHDOG_NOWAYOUT;
74 module_param(nowayout, bool, 0);
75 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
76 	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
77 
78 
79 static int gef_wdt_toggle_wdc(int enabled_predicate, int field_shift)
80 {
81 	u32 data;
82 	u32 enabled;
83 	int ret = 0;
84 
85 	spin_lock(&gef_wdt_spinlock);
86 	data = ioread32be(gef_wdt_regs);
87 	enabled = (data >> GEF_WDC_ENABLED_SHIFT) & 1;
88 
89 	/* only toggle the requested field if enabled state matches predicate */
90 	if ((enabled ^ enabled_predicate) == 0) {
91 		/* We write a 1, then a 2 -- to the appropriate field */
92 		data = (1 << field_shift) | gef_wdt_count;
93 		iowrite32be(data, gef_wdt_regs);
94 
95 		data = (2 << field_shift) | gef_wdt_count;
96 		iowrite32be(data, gef_wdt_regs);
97 		ret = 1;
98 	}
99 	spin_unlock(&gef_wdt_spinlock);
100 
101 	return ret;
102 }
103 
104 static void gef_wdt_service(void)
105 {
106 	gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
107 		GEF_WDC_SERVICE_SHIFT);
108 }
109 
110 static void gef_wdt_handler_enable(void)
111 {
112 	if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_FALSE,
113 				   GEF_WDC_ENABLE_SHIFT)) {
114 		gef_wdt_service();
115 		pr_notice("watchdog activated\n");
116 	}
117 }
118 
119 static void gef_wdt_handler_disable(void)
120 {
121 	if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
122 				   GEF_WDC_ENABLE_SHIFT))
123 		pr_notice("watchdog deactivated\n");
124 }
125 
126 static void gef_wdt_set_timeout(unsigned int timeout)
127 {
128 	/* maximum bus cycle count is 0xFFFFFFFF */
129 	if (timeout > 0xFFFFFFFF / bus_clk)
130 		timeout = 0xFFFFFFFF / bus_clk;
131 
132 	/* Register only holds upper 24 bits, bit shifted into lower 24 */
133 	gef_wdt_count = (timeout * bus_clk) >> 8;
134 	gef_wdt_timeout = timeout;
135 }
136 
137 
138 static ssize_t gef_wdt_write(struct file *file, const char __user *data,
139 				 size_t len, loff_t *ppos)
140 {
141 	if (len) {
142 		if (!nowayout) {
143 			size_t i;
144 
145 			expect_close = 0;
146 
147 			for (i = 0; i != len; i++) {
148 				char c;
149 				if (get_user(c, data + i))
150 					return -EFAULT;
151 				if (c == 'V')
152 					expect_close = 42;
153 			}
154 		}
155 		gef_wdt_service();
156 	}
157 
158 	return len;
159 }
160 
161 static long gef_wdt_ioctl(struct file *file, unsigned int cmd,
162 							unsigned long arg)
163 {
164 	int timeout;
165 	int options;
166 	void __user *argp = (void __user *)arg;
167 	static const struct watchdog_info info = {
168 		.options =	WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
169 				WDIOF_KEEPALIVEPING,
170 		.firmware_version = 0,
171 		.identity = "GE watchdog",
172 	};
173 
174 	switch (cmd) {
175 	case WDIOC_GETSUPPORT:
176 		if (copy_to_user(argp, &info, sizeof(info)))
177 			return -EFAULT;
178 		break;
179 
180 	case WDIOC_GETSTATUS:
181 	case WDIOC_GETBOOTSTATUS:
182 		if (put_user(wdt_status, (int __user *)argp))
183 			return -EFAULT;
184 		wdt_status &= ~WDIOF_KEEPALIVEPING;
185 		break;
186 
187 	case WDIOC_SETOPTIONS:
188 		if (get_user(options, (int __user *)argp))
189 			return -EFAULT;
190 
191 		if (options & WDIOS_DISABLECARD)
192 			gef_wdt_handler_disable();
193 
194 		if (options & WDIOS_ENABLECARD)
195 			gef_wdt_handler_enable();
196 		break;
197 
198 	case WDIOC_KEEPALIVE:
199 		gef_wdt_service();
200 		wdt_status |= WDIOF_KEEPALIVEPING;
201 		break;
202 
203 	case WDIOC_SETTIMEOUT:
204 		if (get_user(timeout, (int __user *)argp))
205 			return -EFAULT;
206 		gef_wdt_set_timeout(timeout);
207 		/* Fall through */
208 
209 	case WDIOC_GETTIMEOUT:
210 		if (put_user(gef_wdt_timeout, (int __user *)argp))
211 			return -EFAULT;
212 		break;
213 
214 	default:
215 		return -ENOTTY;
216 	}
217 
218 	return 0;
219 }
220 
221 static int gef_wdt_open(struct inode *inode, struct file *file)
222 {
223 	if (test_and_set_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags))
224 		return -EBUSY;
225 
226 	if (nowayout)
227 		__module_get(THIS_MODULE);
228 
229 	gef_wdt_handler_enable();
230 
231 	return nonseekable_open(inode, file);
232 }
233 
234 static int gef_wdt_release(struct inode *inode, struct file *file)
235 {
236 	if (expect_close == 42)
237 		gef_wdt_handler_disable();
238 	else {
239 		pr_crit("unexpected close, not stopping timer!\n");
240 		gef_wdt_service();
241 	}
242 	expect_close = 0;
243 
244 	clear_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags);
245 
246 	return 0;
247 }
248 
249 static const struct file_operations gef_wdt_fops = {
250 	.owner = THIS_MODULE,
251 	.llseek = no_llseek,
252 	.write = gef_wdt_write,
253 	.unlocked_ioctl = gef_wdt_ioctl,
254 	.open = gef_wdt_open,
255 	.release = gef_wdt_release,
256 };
257 
258 static struct miscdevice gef_wdt_miscdev = {
259 	.minor = WATCHDOG_MINOR,
260 	.name = "watchdog",
261 	.fops = &gef_wdt_fops,
262 };
263 
264 
265 static int gef_wdt_probe(struct platform_device *dev)
266 {
267 	int timeout = 10;
268 	u32 freq;
269 
270 	bus_clk = 133; /* in MHz */
271 
272 	freq = fsl_get_sys_freq();
273 	if (freq != -1)
274 		bus_clk = freq;
275 
276 	/* Map devices registers into memory */
277 	gef_wdt_regs = of_iomap(dev->dev.of_node, 0);
278 	if (gef_wdt_regs == NULL)
279 		return -ENOMEM;
280 
281 	gef_wdt_set_timeout(timeout);
282 
283 	gef_wdt_handler_disable();	/* in case timer was already running */
284 
285 	return misc_register(&gef_wdt_miscdev);
286 }
287 
288 static int gef_wdt_remove(struct platform_device *dev)
289 {
290 	misc_deregister(&gef_wdt_miscdev);
291 
292 	gef_wdt_handler_disable();
293 
294 	iounmap(gef_wdt_regs);
295 
296 	return 0;
297 }
298 
299 static const struct of_device_id gef_wdt_ids[] = {
300 	{
301 		.compatible = "gef,fpga-wdt",
302 	},
303 	{},
304 };
305 
306 static struct platform_driver gef_wdt_driver = {
307 	.driver = {
308 		.name = "gef_wdt",
309 		.owner = THIS_MODULE,
310 		.of_match_table = gef_wdt_ids,
311 	},
312 	.probe		= gef_wdt_probe,
313 };
314 
315 static int __init gef_wdt_init(void)
316 {
317 	pr_info("GE watchdog driver\n");
318 	return platform_driver_register(&gef_wdt_driver);
319 }
320 
321 static void __exit gef_wdt_exit(void)
322 {
323 	platform_driver_unregister(&gef_wdt_driver);
324 }
325 
326 module_init(gef_wdt_init);
327 module_exit(gef_wdt_exit);
328 
329 MODULE_AUTHOR("Martyn Welch <martyn.welch@ge.com>");
330 MODULE_DESCRIPTION("GE watchdog driver");
331 MODULE_LICENSE("GPL");
332 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
333 MODULE_ALIAS("platform:gef_wdt");
334