xref: /linux/drivers/watchdog/exar_wdt.c (revision 7ae9fb1b7ecbb5d85d07857943f677fd1a559b18)
1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  *	exar_wdt.c - Driver for the watchdog present in some
4  *		     Exar/MaxLinear UART chips like the XR28V38x.
5  *
6  *	(c) Copyright 2022 D. Müller <d.mueller@elsoft.ch>.
7  *
8  */
9 
10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11 
12 #include <linux/io.h>
13 #include <linux/list.h>
14 #include <linux/module.h>
15 #include <linux/platform_device.h>
16 #include <linux/slab.h>
17 #include <linux/watchdog.h>
18 
19 #define DRV_NAME	"exar_wdt"
20 
21 static const unsigned short sio_config_ports[] = { 0x2e, 0x4e };
22 static const unsigned char sio_enter_keys[] = { 0x67, 0x77, 0x87, 0xA0 };
23 #define EXAR_EXIT_KEY	0xAA
24 
25 #define EXAR_LDN	0x07
26 #define EXAR_DID	0x20
27 #define EXAR_VID	0x23
28 #define EXAR_WDT	0x26
29 #define EXAR_ACT	0x30
30 #define EXAR_RTBASE	0x60
31 
32 #define EXAR_WDT_LDEV	0x08
33 
34 #define EXAR_VEN_ID	0x13A8
35 #define EXAR_DEV_382	0x0382
36 #define EXAR_DEV_384	0x0384
37 
38 /* WDT runtime registers */
39 #define WDT_CTRL	0x00
40 #define WDT_VAL		0x01
41 
42 #define WDT_UNITS_10MS	0x0	/* the 10 millisec unit of the HW is not used */
43 #define WDT_UNITS_SEC	0x2
44 #define WDT_UNITS_MIN	0x4
45 
46 /* default WDT control for WDTOUT signal activ / rearm by read */
47 #define EXAR_WDT_DEF_CONF	0
48 
49 struct wdt_pdev_node {
50 	struct list_head list;
51 	struct platform_device *pdev;
52 	const char name[16];
53 };
54 
55 struct wdt_priv {
56 	/* the lock for WDT io operations */
57 	spinlock_t io_lock;
58 	struct resource wdt_res;
59 	struct watchdog_device wdt_dev;
60 	unsigned short did;
61 	unsigned short config_port;
62 	unsigned char enter_key;
63 	unsigned char unit;
64 	unsigned char timeout;
65 };
66 
67 #define WATCHDOG_TIMEOUT 60
68 
69 static int timeout = WATCHDOG_TIMEOUT;
70 module_param(timeout, int, 0);
71 MODULE_PARM_DESC(timeout,
72 		 "Watchdog timeout in seconds. 1<=timeout<=15300, default="
73 		 __MODULE_STRING(WATCHDOG_TIMEOUT) ".");
74 
75 static bool nowayout = WATCHDOG_NOWAYOUT;
76 module_param(nowayout, bool, 0);
77 MODULE_PARM_DESC(nowayout,
78 		 "Watchdog cannot be stopped once started (default="
79 		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
80 
exar_sio_enter(const unsigned short config_port,const unsigned char key)81 static int exar_sio_enter(const unsigned short config_port,
82 			  const unsigned char key)
83 {
84 	if (!request_muxed_region(config_port, 2, DRV_NAME))
85 		return -EBUSY;
86 
87 	/* write the ENTER-KEY twice */
88 	outb(key, config_port);
89 	outb(key, config_port);
90 
91 	return 0;
92 }
93 
exar_sio_exit(const unsigned short config_port)94 static void exar_sio_exit(const unsigned short config_port)
95 {
96 	outb(EXAR_EXIT_KEY, config_port);
97 	release_region(config_port, 2);
98 }
99 
exar_sio_read(const unsigned short config_port,const unsigned char reg)100 static unsigned char exar_sio_read(const unsigned short config_port,
101 				   const unsigned char reg)
102 {
103 	outb(reg, config_port);
104 	return inb(config_port + 1);
105 }
106 
exar_sio_write(const unsigned short config_port,const unsigned char reg,const unsigned char val)107 static void exar_sio_write(const unsigned short config_port,
108 			   const unsigned char reg, const unsigned char val)
109 {
110 	outb(reg, config_port);
111 	outb(val, config_port + 1);
112 }
113 
exar_sio_read16(const unsigned short config_port,const unsigned char reg)114 static unsigned short exar_sio_read16(const unsigned short config_port,
115 				      const unsigned char reg)
116 {
117 	unsigned char msb, lsb;
118 
119 	msb = exar_sio_read(config_port, reg);
120 	lsb = exar_sio_read(config_port, reg + 1);
121 
122 	return (msb << 8) | lsb;
123 }
124 
exar_sio_select_wdt(const unsigned short config_port)125 static void exar_sio_select_wdt(const unsigned short config_port)
126 {
127 	exar_sio_write(config_port, EXAR_LDN, EXAR_WDT_LDEV);
128 }
129 
exar_wdt_arm(const struct wdt_priv * priv)130 static void exar_wdt_arm(const struct wdt_priv *priv)
131 {
132 	unsigned short rt_base = priv->wdt_res.start;
133 
134 	/* write timeout value twice to arm watchdog */
135 	outb(priv->timeout, rt_base + WDT_VAL);
136 	outb(priv->timeout, rt_base + WDT_VAL);
137 }
138 
exar_wdt_disarm(const struct wdt_priv * priv)139 static void exar_wdt_disarm(const struct wdt_priv *priv)
140 {
141 	unsigned short rt_base = priv->wdt_res.start;
142 
143 	/*
144 	 * use two accesses with different values to make sure
145 	 * that a combination of a previous single access and
146 	 * the ones below with the same value are not falsely
147 	 * interpreted as "arm watchdog"
148 	 */
149 	outb(0xFF, rt_base + WDT_VAL);
150 	outb(0, rt_base + WDT_VAL);
151 }
152 
exar_wdt_start(struct watchdog_device * wdog)153 static int exar_wdt_start(struct watchdog_device *wdog)
154 {
155 	struct wdt_priv *priv = watchdog_get_drvdata(wdog);
156 	unsigned short rt_base = priv->wdt_res.start;
157 
158 	spin_lock(&priv->io_lock);
159 
160 	exar_wdt_disarm(priv);
161 	outb(priv->unit, rt_base + WDT_CTRL);
162 	exar_wdt_arm(priv);
163 
164 	spin_unlock(&priv->io_lock);
165 	return 0;
166 }
167 
exar_wdt_stop(struct watchdog_device * wdog)168 static int exar_wdt_stop(struct watchdog_device *wdog)
169 {
170 	struct wdt_priv *priv = watchdog_get_drvdata(wdog);
171 
172 	spin_lock(&priv->io_lock);
173 
174 	exar_wdt_disarm(priv);
175 
176 	spin_unlock(&priv->io_lock);
177 	return 0;
178 }
179 
exar_wdt_keepalive(struct watchdog_device * wdog)180 static int exar_wdt_keepalive(struct watchdog_device *wdog)
181 {
182 	struct wdt_priv *priv = watchdog_get_drvdata(wdog);
183 	unsigned short rt_base = priv->wdt_res.start;
184 
185 	spin_lock(&priv->io_lock);
186 
187 	/* reading the WDT_VAL reg will feed the watchdog */
188 	inb(rt_base + WDT_VAL);
189 
190 	spin_unlock(&priv->io_lock);
191 	return 0;
192 }
193 
exar_wdt_set_timeout(struct watchdog_device * wdog,unsigned int t)194 static int exar_wdt_set_timeout(struct watchdog_device *wdog, unsigned int t)
195 {
196 	struct wdt_priv *priv = watchdog_get_drvdata(wdog);
197 	bool unit_min = false;
198 
199 	/*
200 	 * if new timeout is bigger then 255 seconds, change the
201 	 * unit to minutes and round the timeout up to the next whole minute
202 	 */
203 	if (t > 255) {
204 		unit_min = true;
205 		t = DIV_ROUND_UP(t, 60);
206 	}
207 
208 	/* save for later use in exar_wdt_start() */
209 	priv->unit = unit_min ? WDT_UNITS_MIN : WDT_UNITS_SEC;
210 	priv->timeout = t;
211 
212 	wdog->timeout = unit_min ? t * 60 : t;
213 
214 	if (watchdog_hw_running(wdog))
215 		exar_wdt_start(wdog);
216 
217 	return 0;
218 }
219 
220 static const struct watchdog_info exar_wdt_info = {
221 	.options	= WDIOF_KEEPALIVEPING |
222 			  WDIOF_SETTIMEOUT |
223 			  WDIOF_MAGICCLOSE,
224 	.identity	= "Exar/MaxLinear XR28V38x Watchdog",
225 };
226 
227 static const struct watchdog_ops exar_wdt_ops = {
228 	.owner		= THIS_MODULE,
229 	.start		= exar_wdt_start,
230 	.stop		= exar_wdt_stop,
231 	.ping		= exar_wdt_keepalive,
232 	.set_timeout	= exar_wdt_set_timeout,
233 };
234 
exar_wdt_config(struct watchdog_device * wdog,const unsigned char conf)235 static int exar_wdt_config(struct watchdog_device *wdog,
236 			   const unsigned char conf)
237 {
238 	struct wdt_priv *priv = watchdog_get_drvdata(wdog);
239 	int ret;
240 
241 	ret = exar_sio_enter(priv->config_port, priv->enter_key);
242 	if (ret)
243 		return ret;
244 
245 	exar_sio_select_wdt(priv->config_port);
246 	exar_sio_write(priv->config_port, EXAR_WDT, conf);
247 
248 	exar_sio_exit(priv->config_port);
249 
250 	return 0;
251 }
252 
exar_wdt_probe(struct platform_device * pdev)253 static int __init exar_wdt_probe(struct platform_device *pdev)
254 {
255 	struct device *dev = &pdev->dev;
256 	struct wdt_priv *priv = dev->platform_data;
257 	struct watchdog_device *wdt_dev = &priv->wdt_dev;
258 	struct resource *res;
259 	int ret;
260 
261 	res = platform_get_resource(pdev, IORESOURCE_IO, 0);
262 	if (!res)
263 		return -ENXIO;
264 
265 	spin_lock_init(&priv->io_lock);
266 
267 	wdt_dev->info = &exar_wdt_info;
268 	wdt_dev->ops = &exar_wdt_ops;
269 	wdt_dev->min_timeout = 1;
270 	wdt_dev->max_timeout = 255 * 60;
271 
272 	watchdog_init_timeout(wdt_dev, timeout, NULL);
273 	watchdog_set_nowayout(wdt_dev, nowayout);
274 	watchdog_stop_on_reboot(wdt_dev);
275 	watchdog_stop_on_unregister(wdt_dev);
276 	watchdog_set_drvdata(wdt_dev, priv);
277 
278 	ret = exar_wdt_config(wdt_dev, EXAR_WDT_DEF_CONF);
279 	if (ret)
280 		return ret;
281 
282 	exar_wdt_set_timeout(wdt_dev, timeout);
283 	/* Make sure that the watchdog is not running */
284 	exar_wdt_stop(wdt_dev);
285 
286 	ret = devm_watchdog_register_device(dev, wdt_dev);
287 	if (ret)
288 		return ret;
289 
290 	dev_info(dev, "XR28V%X WDT initialized. timeout=%d sec (nowayout=%d)\n",
291 		 priv->did, timeout, nowayout);
292 
293 	return 0;
294 }
295 
exar_detect(const unsigned short config_port,const unsigned char key,unsigned short * rt_base)296 static unsigned short __init exar_detect(const unsigned short config_port,
297 					 const unsigned char key,
298 					 unsigned short *rt_base)
299 {
300 	int ret;
301 	unsigned short base = 0;
302 	unsigned short vid, did;
303 
304 	ret = exar_sio_enter(config_port, key);
305 	if (ret)
306 		return 0;
307 
308 	vid = exar_sio_read16(config_port, EXAR_VID);
309 	did = exar_sio_read16(config_port, EXAR_DID);
310 
311 	/* check for the vendor and device IDs we currently know about */
312 	if (vid == EXAR_VEN_ID &&
313 	    (did == EXAR_DEV_382 ||
314 	     did == EXAR_DEV_384)) {
315 		exar_sio_select_wdt(config_port);
316 		/* is device active? */
317 		if (exar_sio_read(config_port, EXAR_ACT) == 0x01)
318 			base = exar_sio_read16(config_port, EXAR_RTBASE);
319 	}
320 
321 	exar_sio_exit(config_port);
322 
323 	if (base) {
324 		pr_debug("Found a XR28V%X WDT (conf: 0x%x / rt: 0x%04x)\n",
325 			 did, config_port, base);
326 		*rt_base = base;
327 		return did;
328 	}
329 
330 	return 0;
331 }
332 
333 static struct platform_driver exar_wdt_driver = {
334 	.driver = {
335 		.name = DRV_NAME,
336 	},
337 };
338 
339 static LIST_HEAD(pdev_list);
340 
exar_wdt_register(struct wdt_priv * priv,const int idx)341 static int __init exar_wdt_register(struct wdt_priv *priv, const int idx)
342 {
343 	struct wdt_pdev_node *n;
344 
345 	n = kzalloc(sizeof(*n), GFP_KERNEL);
346 	if (!n)
347 		return -ENOMEM;
348 
349 	INIT_LIST_HEAD(&n->list);
350 
351 	scnprintf((char *)n->name, sizeof(n->name), DRV_NAME ".%d", idx);
352 	priv->wdt_res.name = n->name;
353 
354 	n->pdev = platform_device_register_resndata(NULL, DRV_NAME, idx,
355 						    &priv->wdt_res, 1,
356 						    priv, sizeof(*priv));
357 	if (IS_ERR(n->pdev)) {
358 		int err = PTR_ERR(n->pdev);
359 
360 		kfree(n);
361 		return err;
362 	}
363 
364 	list_add_tail(&n->list, &pdev_list);
365 
366 	return 0;
367 }
368 
exar_wdt_unregister(void)369 static void exar_wdt_unregister(void)
370 {
371 	struct wdt_pdev_node *n, *t;
372 
373 	list_for_each_entry_safe(n, t, &pdev_list, list) {
374 		platform_device_unregister(n->pdev);
375 		list_del(&n->list);
376 		kfree(n);
377 	}
378 }
379 
exar_wdt_init(void)380 static int __init exar_wdt_init(void)
381 {
382 	int ret, i, j, idx = 0;
383 
384 	/* search for active Exar watchdogs on all possible locations */
385 	for (i = 0; i < ARRAY_SIZE(sio_config_ports); i++) {
386 		for (j = 0; j < ARRAY_SIZE(sio_enter_keys); j++) {
387 			unsigned short did, rt_base = 0;
388 
389 			did = exar_detect(sio_config_ports[i],
390 					  sio_enter_keys[j],
391 					  &rt_base);
392 
393 			if (did) {
394 				struct wdt_priv priv = {
395 					.wdt_res = DEFINE_RES_IO(rt_base, 2),
396 					.did = did,
397 					.config_port = sio_config_ports[i],
398 					.enter_key = sio_enter_keys[j],
399 				};
400 
401 				ret = exar_wdt_register(&priv, idx);
402 				if (!ret)
403 					idx++;
404 			}
405 		}
406 	}
407 
408 	if (!idx)
409 		return -ENODEV;
410 
411 	ret = platform_driver_probe(&exar_wdt_driver, exar_wdt_probe);
412 	if (ret)
413 		exar_wdt_unregister();
414 
415 	return ret;
416 }
417 
exar_wdt_exit(void)418 static void __exit exar_wdt_exit(void)
419 {
420 	exar_wdt_unregister();
421 	platform_driver_unregister(&exar_wdt_driver);
422 }
423 
424 module_init(exar_wdt_init);
425 module_exit(exar_wdt_exit);
426 
427 MODULE_AUTHOR("David Müller <d.mueller@elsoft.ch>");
428 MODULE_DESCRIPTION("Exar/MaxLinear Watchdog Driver");
429 MODULE_LICENSE("GPL");
430