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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 <[email protected]>.
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
21static const unsigned short sio_config_ports[] = { 0x2e, 0x4e };
22static 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
49struct wdt_pdev_node {
50 struct list_head list;
51 struct platform_device *pdev;
52 const char name[16];
53};
54
55struct 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
69static int timeout = WATCHDOG_TIMEOUT;
70module_param(timeout, int, 0);
71MODULE_PARM_DESC(timeout,
72 "Watchdog timeout in seconds. 1<=timeout<=15300, default="
73 __MODULE_STRING(WATCHDOG_TIMEOUT) ".");
74
75static bool nowayout = WATCHDOG_NOWAYOUT;
76module_param(nowayout, bool, 0);
77MODULE_PARM_DESC(nowayout,
78 "Watchdog cannot be stopped once started (default="
79 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
80
81static 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
94static 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
100static 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
107static 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
114static 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
125static void exar_sio_select_wdt(const unsigned short config_port)
126{
127 exar_sio_write(config_port, EXAR_LDN, EXAR_WDT_LDEV);
128}
129
130static 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
139static 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
153static 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
168static 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
180static 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
194static 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
220static const struct watchdog_info exar_wdt_info = {
221 .options = WDIOF_KEEPALIVEPING |
222 WDIOF_SETTIMEOUT |
223 WDIOF_MAGICCLOSE,
224 .identity = "Exar XR28V38x Watchdog",
225};
226
227static 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
235static 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
253static 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
296static 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
333static struct platform_driver exar_wdt_driver = {
334 .driver = {
335 .name = DRV_NAME,
336 },
337};
338
339static LIST_HEAD(pdev_list);
340
341static int __init exar_wdt_register(struct wdt_priv *priv, const int idx)
342{
343 struct wdt_pdev_node *n;
344
345 n = kzalloc_obj(*n);
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
369static 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
380static 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
418static void __exit exar_wdt_exit(void)
419{
420 exar_wdt_unregister();
421 platform_driver_unregister(&exar_wdt_driver);
422}
423
424module_init(exar_wdt_init);
425module_exit(exar_wdt_exit);
426
427MODULE_AUTHOR("David Müller <[email protected]>");
428MODULE_DESCRIPTION("Exar/MaxLinear Watchdog Driver");
429MODULE_LICENSE("GPL");