xref: /linux/drivers/watchdog/gef_wdt.c (revision 63307d015b91e626c97bb82e88054af3d0b74643) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * GE watchdog userspace interface
4  *
5  * Author:  Martyn Welch <martyn.welch@ge.com>
6  *
7  * Copyright 2008 GE Intelligent Platforms Embedded Systems, Inc.
8  *
9  * Based on: mv64x60_wdt.c (MV64X60 watchdog userspace interface)
10  *   Author: James Chapman <jchapman@katalix.com>
11  */
12 
13 /* TODO:
14  * This driver does not provide support for the hardwares capability of sending
15  * an interrupt at a programmable threshold.
16  *
17  * This driver currently can only support 1 watchdog - there are 2 in the
18  * hardware that this driver supports. Thus one could be configured as a
19  * process-based watchdog (via /dev/watchdog), the second (using the interrupt
20  * capabilities) a kernel-based watchdog.
21  */
22 
23 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
24 
25 #include <linux/kernel.h>
26 #include <linux/compiler.h>
27 #include <linux/init.h>
28 #include <linux/module.h>
29 #include <linux/miscdevice.h>
30 #include <linux/watchdog.h>
31 #include <linux/fs.h>
32 #include <linux/of.h>
33 #include <linux/of_address.h>
34 #include <linux/of_platform.h>
35 #include <linux/io.h>
36 #include <linux/uaccess.h>
37 
38 #include <sysdev/fsl_soc.h>
39 
40 /*
41  * The watchdog configuration register contains a pair of 2-bit fields,
42  *   1.  a reload field, bits 27-26, which triggers a reload of
43  *       the countdown register, and
44  *   2.  an enable field, bits 25-24, which toggles between
45  *       enabling and disabling the watchdog timer.
46  * Bit 31 is a read-only field which indicates whether the
47  * watchdog timer is currently enabled.
48  *
49  * The low 24 bits contain the timer reload value.
50  */
51 #define GEF_WDC_ENABLE_SHIFT	24
52 #define GEF_WDC_SERVICE_SHIFT	26
53 #define GEF_WDC_ENABLED_SHIFT	31
54 
55 #define GEF_WDC_ENABLED_TRUE	1
56 #define GEF_WDC_ENABLED_FALSE	0
57 
58 /* Flags bits */
59 #define GEF_WDOG_FLAG_OPENED	0
60 
61 static unsigned long wdt_flags;
62 static int wdt_status;
63 static void __iomem *gef_wdt_regs;
64 static int gef_wdt_timeout;
65 static int gef_wdt_count;
66 static unsigned int bus_clk;
67 static char expect_close;
68 static DEFINE_SPINLOCK(gef_wdt_spinlock);
69 
70 static bool nowayout = WATCHDOG_NOWAYOUT;
71 module_param(nowayout, bool, 0);
72 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
73 	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
74 
75 
76 static int gef_wdt_toggle_wdc(int enabled_predicate, int field_shift)
77 {
78 	u32 data;
79 	u32 enabled;
80 	int ret = 0;
81 
82 	spin_lock(&gef_wdt_spinlock);
83 	data = ioread32be(gef_wdt_regs);
84 	enabled = (data >> GEF_WDC_ENABLED_SHIFT) & 1;
85 
86 	/* only toggle the requested field if enabled state matches predicate */
87 	if ((enabled ^ enabled_predicate) == 0) {
88 		/* We write a 1, then a 2 -- to the appropriate field */
89 		data = (1 << field_shift) | gef_wdt_count;
90 		iowrite32be(data, gef_wdt_regs);
91 
92 		data = (2 << field_shift) | gef_wdt_count;
93 		iowrite32be(data, gef_wdt_regs);
94 		ret = 1;
95 	}
96 	spin_unlock(&gef_wdt_spinlock);
97 
98 	return ret;
99 }
100 
101 static void gef_wdt_service(void)
102 {
103 	gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
104 		GEF_WDC_SERVICE_SHIFT);
105 }
106 
107 static void gef_wdt_handler_enable(void)
108 {
109 	if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_FALSE,
110 				   GEF_WDC_ENABLE_SHIFT)) {
111 		gef_wdt_service();
112 		pr_notice("watchdog activated\n");
113 	}
114 }
115 
116 static void gef_wdt_handler_disable(void)
117 {
118 	if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
119 				   GEF_WDC_ENABLE_SHIFT))
120 		pr_notice("watchdog deactivated\n");
121 }
122 
123 static void gef_wdt_set_timeout(unsigned int timeout)
124 {
125 	/* maximum bus cycle count is 0xFFFFFFFF */
126 	if (timeout > 0xFFFFFFFF / bus_clk)
127 		timeout = 0xFFFFFFFF / bus_clk;
128 
129 	/* Register only holds upper 24 bits, bit shifted into lower 24 */
130 	gef_wdt_count = (timeout * bus_clk) >> 8;
131 	gef_wdt_timeout = timeout;
132 }
133 
134 
135 static ssize_t gef_wdt_write(struct file *file, const char __user *data,
136 				 size_t len, loff_t *ppos)
137 {
138 	if (len) {
139 		if (!nowayout) {
140 			size_t i;
141 
142 			expect_close = 0;
143 
144 			for (i = 0; i != len; i++) {
145 				char c;
146 				if (get_user(c, data + i))
147 					return -EFAULT;
148 				if (c == 'V')
149 					expect_close = 42;
150 			}
151 		}
152 		gef_wdt_service();
153 	}
154 
155 	return len;
156 }
157 
158 static long gef_wdt_ioctl(struct file *file, unsigned int cmd,
159 							unsigned long arg)
160 {
161 	int timeout;
162 	int options;
163 	void __user *argp = (void __user *)arg;
164 	static const struct watchdog_info info = {
165 		.options =	WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
166 				WDIOF_KEEPALIVEPING,
167 		.firmware_version = 0,
168 		.identity = "GE watchdog",
169 	};
170 
171 	switch (cmd) {
172 	case WDIOC_GETSUPPORT:
173 		if (copy_to_user(argp, &info, sizeof(info)))
174 			return -EFAULT;
175 		break;
176 
177 	case WDIOC_GETSTATUS:
178 	case WDIOC_GETBOOTSTATUS:
179 		if (put_user(wdt_status, (int __user *)argp))
180 			return -EFAULT;
181 		wdt_status &= ~WDIOF_KEEPALIVEPING;
182 		break;
183 
184 	case WDIOC_SETOPTIONS:
185 		if (get_user(options, (int __user *)argp))
186 			return -EFAULT;
187 
188 		if (options & WDIOS_DISABLECARD)
189 			gef_wdt_handler_disable();
190 
191 		if (options & WDIOS_ENABLECARD)
192 			gef_wdt_handler_enable();
193 		break;
194 
195 	case WDIOC_KEEPALIVE:
196 		gef_wdt_service();
197 		wdt_status |= WDIOF_KEEPALIVEPING;
198 		break;
199 
200 	case WDIOC_SETTIMEOUT:
201 		if (get_user(timeout, (int __user *)argp))
202 			return -EFAULT;
203 		gef_wdt_set_timeout(timeout);
204 		/* Fall through */
205 
206 	case WDIOC_GETTIMEOUT:
207 		if (put_user(gef_wdt_timeout, (int __user *)argp))
208 			return -EFAULT;
209 		break;
210 
211 	default:
212 		return -ENOTTY;
213 	}
214 
215 	return 0;
216 }
217 
218 static int gef_wdt_open(struct inode *inode, struct file *file)
219 {
220 	if (test_and_set_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags))
221 		return -EBUSY;
222 
223 	if (nowayout)
224 		__module_get(THIS_MODULE);
225 
226 	gef_wdt_handler_enable();
227 
228 	return stream_open(inode, file);
229 }
230 
231 static int gef_wdt_release(struct inode *inode, struct file *file)
232 {
233 	if (expect_close == 42)
234 		gef_wdt_handler_disable();
235 	else {
236 		pr_crit("unexpected close, not stopping timer!\n");
237 		gef_wdt_service();
238 	}
239 	expect_close = 0;
240 
241 	clear_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags);
242 
243 	return 0;
244 }
245 
246 static const struct file_operations gef_wdt_fops = {
247 	.owner = THIS_MODULE,
248 	.llseek = no_llseek,
249 	.write = gef_wdt_write,
250 	.unlocked_ioctl = gef_wdt_ioctl,
251 	.open = gef_wdt_open,
252 	.release = gef_wdt_release,
253 };
254 
255 static struct miscdevice gef_wdt_miscdev = {
256 	.minor = WATCHDOG_MINOR,
257 	.name = "watchdog",
258 	.fops = &gef_wdt_fops,
259 };
260 
261 
262 static int gef_wdt_probe(struct platform_device *dev)
263 {
264 	int timeout = 10;
265 	u32 freq;
266 
267 	bus_clk = 133; /* in MHz */
268 
269 	freq = fsl_get_sys_freq();
270 	if (freq != -1)
271 		bus_clk = freq;
272 
273 	/* Map devices registers into memory */
274 	gef_wdt_regs = of_iomap(dev->dev.of_node, 0);
275 	if (gef_wdt_regs == NULL)
276 		return -ENOMEM;
277 
278 	gef_wdt_set_timeout(timeout);
279 
280 	gef_wdt_handler_disable();	/* in case timer was already running */
281 
282 	return misc_register(&gef_wdt_miscdev);
283 }
284 
285 static int gef_wdt_remove(struct platform_device *dev)
286 {
287 	misc_deregister(&gef_wdt_miscdev);
288 
289 	gef_wdt_handler_disable();
290 
291 	iounmap(gef_wdt_regs);
292 
293 	return 0;
294 }
295 
296 static const struct of_device_id gef_wdt_ids[] = {
297 	{
298 		.compatible = "gef,fpga-wdt",
299 	},
300 	{},
301 };
302 MODULE_DEVICE_TABLE(of, gef_wdt_ids);
303 
304 static struct platform_driver gef_wdt_driver = {
305 	.driver = {
306 		.name = "gef_wdt",
307 		.of_match_table = gef_wdt_ids,
308 	},
309 	.probe		= gef_wdt_probe,
310 	.remove		= gef_wdt_remove,
311 };
312 
313 static int __init gef_wdt_init(void)
314 {
315 	pr_info("GE watchdog driver\n");
316 	return platform_driver_register(&gef_wdt_driver);
317 }
318 
319 static void __exit gef_wdt_exit(void)
320 {
321 	platform_driver_unregister(&gef_wdt_driver);
322 }
323 
324 module_init(gef_wdt_init);
325 module_exit(gef_wdt_exit);
326 
327 MODULE_AUTHOR("Martyn Welch <martyn.welch@ge.com>");
328 MODULE_DESCRIPTION("GE watchdog driver");
329 MODULE_LICENSE("GPL");
330 MODULE_ALIAS("platform:gef_wdt");
331