xref: /linux/drivers/watchdog/cadence_wdt.c (revision f828d5e2487d57699c1b9143619d03f71b164cda) 
1 /*
2  * Cadence WDT driver - Used by Xilinx Zynq
3  *
4  * Copyright (C) 2010 - 2014 Xilinx, Inc.
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License
8  * as published by the Free Software Foundation; either version
9  * 2 of the License, or (at your option) any later version.
10  */
11 
12 #include <linux/clk.h>
13 #include <linux/init.h>
14 #include <linux/interrupt.h>
15 #include <linux/io.h>
16 #include <linux/irq.h>
17 #include <linux/kernel.h>
18 #include <linux/module.h>
19 #include <linux/of.h>
20 #include <linux/platform_device.h>
21 #include <linux/reboot.h>
22 #include <linux/watchdog.h>
23 
24 #define CDNS_WDT_DEFAULT_TIMEOUT	10
25 /* Supports 1 - 516 sec */
26 #define CDNS_WDT_MIN_TIMEOUT	1
27 #define CDNS_WDT_MAX_TIMEOUT	516
28 
29 /* Restart key */
30 #define CDNS_WDT_RESTART_KEY 0x00001999
31 
32 /* Counter register access key */
33 #define CDNS_WDT_REGISTER_ACCESS_KEY 0x00920000
34 
35 /* Counter value divisor */
36 #define CDNS_WDT_COUNTER_VALUE_DIVISOR 0x1000
37 
38 /* Clock prescaler value and selection */
39 #define CDNS_WDT_PRESCALE_64	64
40 #define CDNS_WDT_PRESCALE_512	512
41 #define CDNS_WDT_PRESCALE_4096	4096
42 #define CDNS_WDT_PRESCALE_SELECT_64	1
43 #define CDNS_WDT_PRESCALE_SELECT_512	2
44 #define CDNS_WDT_PRESCALE_SELECT_4096	3
45 
46 /* Input clock frequency */
47 #define CDNS_WDT_CLK_10MHZ	10000000
48 #define CDNS_WDT_CLK_75MHZ	75000000
49 
50 /* Counter maximum value */
51 #define CDNS_WDT_COUNTER_MAX 0xFFF
52 
53 static int wdt_timeout = CDNS_WDT_DEFAULT_TIMEOUT;
54 static int nowayout = WATCHDOG_NOWAYOUT;
55 
56 module_param(wdt_timeout, int, 0);
57 MODULE_PARM_DESC(wdt_timeout,
58 		 "Watchdog time in seconds. (default="
59 		 __MODULE_STRING(CDNS_WDT_DEFAULT_TIMEOUT) ")");
60 
61 module_param(nowayout, int, 0);
62 MODULE_PARM_DESC(nowayout,
63 		 "Watchdog cannot be stopped once started (default="
64 		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
65 
66 /**
67  * struct cdns_wdt - Watchdog device structure
68  * @regs: baseaddress of device
69  * @rst: reset flag
70  * @clk: struct clk * of a clock source
71  * @prescaler: for saving prescaler value
72  * @ctrl_clksel: counter clock prescaler selection
73  * @io_lock: spinlock for IO register access
74  * @cdns_wdt_device: watchdog device structure
75  * @cdns_wdt_notifier: notifier structure
76  *
77  * Structure containing parameters specific to cadence watchdog.
78  */
79 struct cdns_wdt {
80 	void __iomem		*regs;
81 	bool			rst;
82 	struct clk		*clk;
83 	u32			prescaler;
84 	u32			ctrl_clksel;
85 	spinlock_t		io_lock;
86 	struct watchdog_device	cdns_wdt_device;
87 	struct notifier_block	cdns_wdt_notifier;
88 };
89 
90 /* Write access to Registers */
91 static inline void cdns_wdt_writereg(struct cdns_wdt *wdt, u32 offset, u32 val)
92 {
93 	writel_relaxed(val, wdt->regs + offset);
94 }
95 
96 /*************************Register Map**************************************/
97 
98 /* Register Offsets for the WDT */
99 #define CDNS_WDT_ZMR_OFFSET	0x0	/* Zero Mode Register */
100 #define CDNS_WDT_CCR_OFFSET	0x4	/* Counter Control Register */
101 #define CDNS_WDT_RESTART_OFFSET	0x8	/* Restart Register */
102 #define CDNS_WDT_SR_OFFSET	0xC	/* Status Register */
103 
104 /*
105  * Zero Mode Register - This register controls how the time out is indicated
106  * and also contains the access code to allow writes to the register (0xABC).
107  */
108 #define CDNS_WDT_ZMR_WDEN_MASK	0x00000001 /* Enable the WDT */
109 #define CDNS_WDT_ZMR_RSTEN_MASK	0x00000002 /* Enable the reset output */
110 #define CDNS_WDT_ZMR_IRQEN_MASK	0x00000004 /* Enable IRQ output */
111 #define CDNS_WDT_ZMR_RSTLEN_16	0x00000030 /* Reset pulse of 16 pclk cycles */
112 #define CDNS_WDT_ZMR_ZKEY_VAL	0x00ABC000 /* Access key, 0xABC << 12 */
113 /*
114  * Counter Control register - This register controls how fast the timer runs
115  * and the reset value and also contains the access code to allow writes to
116  * the register.
117  */
118 #define CDNS_WDT_CCR_CRV_MASK	0x00003FFC /* Counter reset value */
119 
120 /**
121  * cdns_wdt_stop - Stop the watchdog.
122  *
123  * @wdd: watchdog device
124  *
125  * Read the contents of the ZMR register, clear the WDEN bit
126  * in the register and set the access key for successful write.
127  *
128  * Return: always 0
129  */
130 static int cdns_wdt_stop(struct watchdog_device *wdd)
131 {
132 	struct cdns_wdt *wdt = watchdog_get_drvdata(wdd);
133 
134 	spin_lock(&wdt->io_lock);
135 	cdns_wdt_writereg(wdt, CDNS_WDT_ZMR_OFFSET,
136 			  CDNS_WDT_ZMR_ZKEY_VAL & (~CDNS_WDT_ZMR_WDEN_MASK));
137 	spin_unlock(&wdt->io_lock);
138 
139 	return 0;
140 }
141 
142 /**
143  * cdns_wdt_reload - Reload the watchdog timer (i.e. pat the watchdog).
144  *
145  * @wdd: watchdog device
146  *
147  * Write the restart key value (0x00001999) to the restart register.
148  *
149  * Return: always 0
150  */
151 static int cdns_wdt_reload(struct watchdog_device *wdd)
152 {
153 	struct cdns_wdt *wdt = watchdog_get_drvdata(wdd);
154 
155 	spin_lock(&wdt->io_lock);
156 	cdns_wdt_writereg(wdt, CDNS_WDT_RESTART_OFFSET,
157 			  CDNS_WDT_RESTART_KEY);
158 	spin_unlock(&wdt->io_lock);
159 
160 	return 0;
161 }
162 
163 /**
164  * cdns_wdt_start - Enable and start the watchdog.
165  *
166  * @wdd: watchdog device
167  *
168  * The counter value is calculated according to the formula:
169  *		calculated count = (timeout * clock) / prescaler + 1.
170  * The calculated count is divided by 0x1000 to obtain the field value
171  * to write to counter control register.
172  * Clears the contents of prescaler and counter reset value. Sets the
173  * prescaler to 4096 and the calculated count and access key
174  * to write to CCR Register.
175  * Sets the WDT (WDEN bit) and either the Reset signal(RSTEN bit)
176  * or Interrupt signal(IRQEN) with a specified cycles and the access
177  * key to write to ZMR Register.
178  *
179  * Return: always 0
180  */
181 static int cdns_wdt_start(struct watchdog_device *wdd)
182 {
183 	struct cdns_wdt *wdt = watchdog_get_drvdata(wdd);
184 	unsigned int data = 0;
185 	unsigned short count;
186 	unsigned long clock_f = clk_get_rate(wdt->clk);
187 
188 	/*
189 	 * Counter value divisor to obtain the value of
190 	 * counter reset to be written to control register.
191 	 */
192 	count = (wdd->timeout * (clock_f / wdt->prescaler)) /
193 		 CDNS_WDT_COUNTER_VALUE_DIVISOR + 1;
194 
195 	if (count > CDNS_WDT_COUNTER_MAX)
196 		count = CDNS_WDT_COUNTER_MAX;
197 
198 	spin_lock(&wdt->io_lock);
199 	cdns_wdt_writereg(wdt, CDNS_WDT_ZMR_OFFSET,
200 			  CDNS_WDT_ZMR_ZKEY_VAL);
201 
202 	count = (count << 2) & CDNS_WDT_CCR_CRV_MASK;
203 
204 	/* Write counter access key first to be able write to register */
205 	data = count | CDNS_WDT_REGISTER_ACCESS_KEY | wdt->ctrl_clksel;
206 	cdns_wdt_writereg(wdt, CDNS_WDT_CCR_OFFSET, data);
207 	data = CDNS_WDT_ZMR_WDEN_MASK | CDNS_WDT_ZMR_RSTLEN_16 |
208 	       CDNS_WDT_ZMR_ZKEY_VAL;
209 
210 	/* Reset on timeout if specified in device tree. */
211 	if (wdt->rst) {
212 		data |= CDNS_WDT_ZMR_RSTEN_MASK;
213 		data &= ~CDNS_WDT_ZMR_IRQEN_MASK;
214 	} else {
215 		data &= ~CDNS_WDT_ZMR_RSTEN_MASK;
216 		data |= CDNS_WDT_ZMR_IRQEN_MASK;
217 	}
218 	cdns_wdt_writereg(wdt, CDNS_WDT_ZMR_OFFSET, data);
219 	cdns_wdt_writereg(wdt, CDNS_WDT_RESTART_OFFSET,
220 			  CDNS_WDT_RESTART_KEY);
221 	spin_unlock(&wdt->io_lock);
222 
223 	return 0;
224 }
225 
226 /**
227  * cdns_wdt_settimeout - Set a new timeout value for the watchdog device.
228  *
229  * @wdd: watchdog device
230  * @new_time: new timeout value that needs to be set
231  * Return: 0 on success
232  *
233  * Update the watchdog_device timeout with new value which is used when
234  * cdns_wdt_start is called.
235  */
236 static int cdns_wdt_settimeout(struct watchdog_device *wdd,
237 			       unsigned int new_time)
238 {
239 	wdd->timeout = new_time;
240 
241 	return cdns_wdt_start(wdd);
242 }
243 
244 /**
245  * cdns_wdt_irq_handler - Notifies of watchdog timeout.
246  *
247  * @irq: interrupt number
248  * @dev_id: pointer to a platform device structure
249  * Return: IRQ_HANDLED
250  *
251  * The handler is invoked when the watchdog times out and a
252  * reset on timeout has not been enabled.
253  */
254 static irqreturn_t cdns_wdt_irq_handler(int irq, void *dev_id)
255 {
256 	struct platform_device *pdev = dev_id;
257 
258 	dev_info(&pdev->dev,
259 		 "Watchdog timed out. Internal reset not enabled\n");
260 
261 	return IRQ_HANDLED;
262 }
263 
264 /*
265  * Info structure used to indicate the features supported by the device
266  * to the upper layers. This is defined in watchdog.h header file.
267  */
268 static struct watchdog_info cdns_wdt_info = {
269 	.identity	= "cdns_wdt watchdog",
270 	.options	= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
271 			  WDIOF_MAGICCLOSE,
272 };
273 
274 /* Watchdog Core Ops */
275 static struct watchdog_ops cdns_wdt_ops = {
276 	.owner = THIS_MODULE,
277 	.start = cdns_wdt_start,
278 	.stop = cdns_wdt_stop,
279 	.ping = cdns_wdt_reload,
280 	.set_timeout = cdns_wdt_settimeout,
281 };
282 
283 /**
284  * cdns_wdt_notify_sys - Notifier for reboot or shutdown.
285  *
286  * @this: handle to notifier block
287  * @code: turn off indicator
288  * @unused: unused
289  * Return: NOTIFY_DONE
290  *
291  * This notifier is invoked whenever the system reboot or shutdown occur
292  * because we need to disable the WDT before system goes down as WDT might
293  * reset on the next boot.
294  */
295 static int cdns_wdt_notify_sys(struct notifier_block *this, unsigned long code,
296 			       void *unused)
297 {
298 	struct cdns_wdt *wdt = container_of(this, struct cdns_wdt,
299 					    cdns_wdt_notifier);
300 	if (code == SYS_DOWN || code == SYS_HALT)
301 		cdns_wdt_stop(&wdt->cdns_wdt_device);
302 
303 	return NOTIFY_DONE;
304 }
305 
306 /************************Platform Operations*****************************/
307 /**
308  * cdns_wdt_probe - Probe call for the device.
309  *
310  * @pdev: handle to the platform device structure.
311  * Return: 0 on success, negative error otherwise.
312  *
313  * It does all the memory allocation and registration for the device.
314  */
315 static int cdns_wdt_probe(struct platform_device *pdev)
316 {
317 	struct resource *res;
318 	int ret, irq;
319 	unsigned long clock_f;
320 	struct cdns_wdt *wdt;
321 	struct watchdog_device *cdns_wdt_device;
322 
323 	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
324 	if (!wdt)
325 		return -ENOMEM;
326 
327 	cdns_wdt_device = &wdt->cdns_wdt_device;
328 	cdns_wdt_device->info = &cdns_wdt_info;
329 	cdns_wdt_device->ops = &cdns_wdt_ops;
330 	cdns_wdt_device->timeout = CDNS_WDT_DEFAULT_TIMEOUT;
331 	cdns_wdt_device->min_timeout = CDNS_WDT_MIN_TIMEOUT;
332 	cdns_wdt_device->max_timeout = CDNS_WDT_MAX_TIMEOUT;
333 
334 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
335 	wdt->regs = devm_ioremap_resource(&pdev->dev, res);
336 	if (IS_ERR(wdt->regs))
337 		return PTR_ERR(wdt->regs);
338 
339 	/* Register the interrupt */
340 	wdt->rst = of_property_read_bool(pdev->dev.of_node, "reset-on-timeout");
341 	irq = platform_get_irq(pdev, 0);
342 	if (!wdt->rst && irq >= 0) {
343 		ret = devm_request_irq(&pdev->dev, irq, cdns_wdt_irq_handler, 0,
344 				       pdev->name, pdev);
345 		if (ret) {
346 			dev_err(&pdev->dev,
347 				"cannot register interrupt handler err=%d\n",
348 				ret);
349 			return ret;
350 		}
351 	}
352 
353 	/* Initialize the members of cdns_wdt structure */
354 	cdns_wdt_device->parent = &pdev->dev;
355 
356 	ret = watchdog_init_timeout(cdns_wdt_device, wdt_timeout, &pdev->dev);
357 	if (ret) {
358 		dev_err(&pdev->dev, "unable to set timeout value\n");
359 		return ret;
360 	}
361 
362 	watchdog_set_nowayout(cdns_wdt_device, nowayout);
363 	watchdog_set_drvdata(cdns_wdt_device, wdt);
364 
365 	wdt->clk = devm_clk_get(&pdev->dev, NULL);
366 	if (IS_ERR(wdt->clk)) {
367 		dev_err(&pdev->dev, "input clock not found\n");
368 		ret = PTR_ERR(wdt->clk);
369 		return ret;
370 	}
371 
372 	ret = clk_prepare_enable(wdt->clk);
373 	if (ret) {
374 		dev_err(&pdev->dev, "unable to enable clock\n");
375 		return ret;
376 	}
377 
378 	clock_f = clk_get_rate(wdt->clk);
379 	if (clock_f <= CDNS_WDT_CLK_75MHZ) {
380 		wdt->prescaler = CDNS_WDT_PRESCALE_512;
381 		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_512;
382 	} else {
383 		wdt->prescaler = CDNS_WDT_PRESCALE_4096;
384 		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_4096;
385 	}
386 
387 	spin_lock_init(&wdt->io_lock);
388 
389 	wdt->cdns_wdt_notifier.notifier_call = &cdns_wdt_notify_sys;
390 	ret = register_reboot_notifier(&wdt->cdns_wdt_notifier);
391 	if (ret != 0) {
392 		dev_err(&pdev->dev, "cannot register reboot notifier err=%d)\n",
393 			ret);
394 		goto err_clk_disable;
395 	}
396 
397 	ret = watchdog_register_device(cdns_wdt_device);
398 	if (ret) {
399 		dev_err(&pdev->dev, "Failed to register wdt device\n");
400 		goto err_clk_disable;
401 	}
402 	platform_set_drvdata(pdev, wdt);
403 
404 	dev_dbg(&pdev->dev, "Xilinx Watchdog Timer at %p with timeout %ds%s\n",
405 		 wdt->regs, cdns_wdt_device->timeout,
406 		 nowayout ? ", nowayout" : "");
407 
408 	return 0;
409 
410 err_clk_disable:
411 	clk_disable_unprepare(wdt->clk);
412 
413 	return ret;
414 }
415 
416 /**
417  * cdns_wdt_remove - Probe call for the device.
418  *
419  * @pdev: handle to the platform device structure.
420  * Return: 0 on success, otherwise negative error.
421  *
422  * Unregister the device after releasing the resources.
423  */
424 static int cdns_wdt_remove(struct platform_device *pdev)
425 {
426 	struct cdns_wdt *wdt = platform_get_drvdata(pdev);
427 
428 	cdns_wdt_stop(&wdt->cdns_wdt_device);
429 	watchdog_unregister_device(&wdt->cdns_wdt_device);
430 	unregister_reboot_notifier(&wdt->cdns_wdt_notifier);
431 	clk_disable_unprepare(wdt->clk);
432 
433 	return 0;
434 }
435 
436 /**
437  * cdns_wdt_shutdown - Stop the device.
438  *
439  * @pdev: handle to the platform structure.
440  *
441  */
442 static void cdns_wdt_shutdown(struct platform_device *pdev)
443 {
444 	struct cdns_wdt *wdt = platform_get_drvdata(pdev);
445 
446 	cdns_wdt_stop(&wdt->cdns_wdt_device);
447 	clk_disable_unprepare(wdt->clk);
448 }
449 
450 /**
451  * cdns_wdt_suspend - Stop the device.
452  *
453  * @dev: handle to the device structure.
454  * Return: 0 always.
455  */
456 static int __maybe_unused cdns_wdt_suspend(struct device *dev)
457 {
458 	struct platform_device *pdev = container_of(dev,
459 			struct platform_device, dev);
460 	struct cdns_wdt *wdt = platform_get_drvdata(pdev);
461 
462 	cdns_wdt_stop(&wdt->cdns_wdt_device);
463 	clk_disable_unprepare(wdt->clk);
464 
465 	return 0;
466 }
467 
468 /**
469  * cdns_wdt_resume - Resume the device.
470  *
471  * @dev: handle to the device structure.
472  * Return: 0 on success, errno otherwise.
473  */
474 static int __maybe_unused cdns_wdt_resume(struct device *dev)
475 {
476 	int ret;
477 	struct platform_device *pdev = container_of(dev,
478 			struct platform_device, dev);
479 	struct cdns_wdt *wdt = platform_get_drvdata(pdev);
480 
481 	ret = clk_prepare_enable(wdt->clk);
482 	if (ret) {
483 		dev_err(dev, "unable to enable clock\n");
484 		return ret;
485 	}
486 	cdns_wdt_start(&wdt->cdns_wdt_device);
487 
488 	return 0;
489 }
490 
491 static SIMPLE_DEV_PM_OPS(cdns_wdt_pm_ops, cdns_wdt_suspend, cdns_wdt_resume);
492 
493 static struct of_device_id cdns_wdt_of_match[] = {
494 	{ .compatible = "cdns,wdt-r1p2", },
495 	{ /* end of table */ }
496 };
497 MODULE_DEVICE_TABLE(of, cdns_wdt_of_match);
498 
499 /* Driver Structure */
500 static struct platform_driver cdns_wdt_driver = {
501 	.probe		= cdns_wdt_probe,
502 	.remove		= cdns_wdt_remove,
503 	.shutdown	= cdns_wdt_shutdown,
504 	.driver		= {
505 		.name	= "cdns-wdt",
506 		.of_match_table = cdns_wdt_of_match,
507 		.pm	= &cdns_wdt_pm_ops,
508 	},
509 };
510 
511 module_platform_driver(cdns_wdt_driver);
512 
513 MODULE_AUTHOR("Xilinx, Inc.");
514 MODULE_DESCRIPTION("Watchdog driver for Cadence WDT");
515 MODULE_LICENSE("GPL");
516