1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Cadence WDT driver - Used by Xilinx Zynq
4  *
5  * Copyright (C) 2010 - 2014 Xilinx, Inc.
6  *
7  */
8 
9 #include <linux/clk.h>
10 #include <linux/init.h>
11 #include <linux/interrupt.h>
12 #include <linux/io.h>
13 #include <linux/irq.h>
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/of.h>
17 #include <linux/platform_device.h>
18 #include <linux/watchdog.h>
19 
20 #define CDNS_WDT_DEFAULT_TIMEOUT	10
21 /* Supports 1 - 516 sec */
22 #define CDNS_WDT_MIN_TIMEOUT	1
23 #define CDNS_WDT_MAX_TIMEOUT	516
24 
25 /* Restart key */
26 #define CDNS_WDT_RESTART_KEY 0x00001999
27 
28 /* Counter register access key */
29 #define CDNS_WDT_REGISTER_ACCESS_KEY 0x00920000
30 
31 /* Counter value divisor */
32 #define CDNS_WDT_COUNTER_VALUE_DIVISOR 0x1000
33 
34 /* Clock prescaler value and selection */
35 #define CDNS_WDT_PRESCALE_64	64
36 #define CDNS_WDT_PRESCALE_512	512
37 #define CDNS_WDT_PRESCALE_4096	4096
38 #define CDNS_WDT_PRESCALE_SELECT_64	1
39 #define CDNS_WDT_PRESCALE_SELECT_512	2
40 #define CDNS_WDT_PRESCALE_SELECT_4096	3
41 
42 /* Input clock frequency */
43 #define CDNS_WDT_CLK_10MHZ	10000000
44 #define CDNS_WDT_CLK_75MHZ	75000000
45 
46 /* Counter maximum value */
47 #define CDNS_WDT_COUNTER_MAX 0xFFF
48 
49 static int wdt_timeout;
50 static int nowayout = WATCHDOG_NOWAYOUT;
51 
52 module_param(wdt_timeout, int, 0644);
53 MODULE_PARM_DESC(wdt_timeout,
54 		 "Watchdog time in seconds. (default="
55 		 __MODULE_STRING(CDNS_WDT_DEFAULT_TIMEOUT) ")");
56 
57 module_param(nowayout, int, 0644);
58 MODULE_PARM_DESC(nowayout,
59 		 "Watchdog cannot be stopped once started (default="
60 		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
61 
62 /**
63  * struct cdns_wdt - Watchdog device structure
64  * @regs: baseaddress of device
65  * @rst: reset flag
66  * @clk: struct clk * of a clock source
67  * @prescaler: for saving prescaler value
68  * @ctrl_clksel: counter clock prescaler selection
69  * @io_lock: spinlock for IO register access
70  * @cdns_wdt_device: watchdog device structure
71  *
72  * Structure containing parameters specific to cadence watchdog.
73  */
74 struct cdns_wdt {
75 	void __iomem		*regs;
76 	bool			rst;
77 	struct clk		*clk;
78 	u32			prescaler;
79 	u32			ctrl_clksel;
80 	spinlock_t		io_lock;
81 	struct watchdog_device	cdns_wdt_device;
82 };
83 
84 /* Write access to Registers */
85 static inline void cdns_wdt_writereg(struct cdns_wdt *wdt, u32 offset, u32 val)
86 {
87 	writel_relaxed(val, wdt->regs + offset);
88 }
89 
90 /*************************Register Map**************************************/
91 
92 /* Register Offsets for the WDT */
93 #define CDNS_WDT_ZMR_OFFSET	0x0	/* Zero Mode Register */
94 #define CDNS_WDT_CCR_OFFSET	0x4	/* Counter Control Register */
95 #define CDNS_WDT_RESTART_OFFSET	0x8	/* Restart Register */
96 #define CDNS_WDT_SR_OFFSET	0xC	/* Status Register */
97 
98 /*
99  * Zero Mode Register - This register controls how the time out is indicated
100  * and also contains the access code to allow writes to the register (0xABC).
101  */
102 #define CDNS_WDT_ZMR_WDEN_MASK	0x00000001 /* Enable the WDT */
103 #define CDNS_WDT_ZMR_RSTEN_MASK	0x00000002 /* Enable the reset output */
104 #define CDNS_WDT_ZMR_IRQEN_MASK	0x00000004 /* Enable IRQ output */
105 #define CDNS_WDT_ZMR_RSTLEN_16	0x00000030 /* Reset pulse of 16 pclk cycles */
106 #define CDNS_WDT_ZMR_ZKEY_VAL	0x00ABC000 /* Access key, 0xABC << 12 */
107 /*
108  * Counter Control register - This register controls how fast the timer runs
109  * and the reset value and also contains the access code to allow writes to
110  * the register.
111  */
112 #define CDNS_WDT_CCR_CRV_MASK	0x00003FFC /* Counter reset value */
113 
114 /**
115  * cdns_wdt_stop - Stop the watchdog.
116  *
117  * @wdd: watchdog device
118  *
119  * Read the contents of the ZMR register, clear the WDEN bit
120  * in the register and set the access key for successful write.
121  *
122  * Return: always 0
123  */
124 static int cdns_wdt_stop(struct watchdog_device *wdd)
125 {
126 	struct cdns_wdt *wdt = watchdog_get_drvdata(wdd);
127 
128 	spin_lock(&wdt->io_lock);
129 	cdns_wdt_writereg(wdt, CDNS_WDT_ZMR_OFFSET,
130 			  CDNS_WDT_ZMR_ZKEY_VAL & (~CDNS_WDT_ZMR_WDEN_MASK));
131 	spin_unlock(&wdt->io_lock);
132 
133 	return 0;
134 }
135 
136 /**
137  * cdns_wdt_reload - Reload the watchdog timer (i.e. pat the watchdog).
138  *
139  * @wdd: watchdog device
140  *
141  * Write the restart key value (0x00001999) to the restart register.
142  *
143  * Return: always 0
144  */
145 static int cdns_wdt_reload(struct watchdog_device *wdd)
146 {
147 	struct cdns_wdt *wdt = watchdog_get_drvdata(wdd);
148 
149 	spin_lock(&wdt->io_lock);
150 	cdns_wdt_writereg(wdt, CDNS_WDT_RESTART_OFFSET,
151 			  CDNS_WDT_RESTART_KEY);
152 	spin_unlock(&wdt->io_lock);
153 
154 	return 0;
155 }
156 
157 /**
158  * cdns_wdt_start - Enable and start the watchdog.
159  *
160  * @wdd: watchdog device
161  *
162  * The counter value is calculated according to the formula:
163  *		calculated count = (timeout * clock) / prescaler + 1.
164  * The calculated count is divided by 0x1000 to obtain the field value
165  * to write to counter control register.
166  * Clears the contents of prescaler and counter reset value. Sets the
167  * prescaler to 4096 and the calculated count and access key
168  * to write to CCR Register.
169  * Sets the WDT (WDEN bit) and either the Reset signal(RSTEN bit)
170  * or Interrupt signal(IRQEN) with a specified cycles and the access
171  * key to write to ZMR Register.
172  *
173  * Return: always 0
174  */
175 static int cdns_wdt_start(struct watchdog_device *wdd)
176 {
177 	struct cdns_wdt *wdt = watchdog_get_drvdata(wdd);
178 	unsigned int data = 0;
179 	unsigned short count;
180 	unsigned long clock_f = clk_get_rate(wdt->clk);
181 
182 	/*
183 	 * Counter value divisor to obtain the value of
184 	 * counter reset to be written to control register.
185 	 */
186 	count = (wdd->timeout * (clock_f / wdt->prescaler)) /
187 		 CDNS_WDT_COUNTER_VALUE_DIVISOR + 1;
188 
189 	if (count > CDNS_WDT_COUNTER_MAX)
190 		count = CDNS_WDT_COUNTER_MAX;
191 
192 	spin_lock(&wdt->io_lock);
193 	cdns_wdt_writereg(wdt, CDNS_WDT_ZMR_OFFSET,
194 			  CDNS_WDT_ZMR_ZKEY_VAL);
195 
196 	count = (count << 2) & CDNS_WDT_CCR_CRV_MASK;
197 
198 	/* Write counter access key first to be able write to register */
199 	data = count | CDNS_WDT_REGISTER_ACCESS_KEY | wdt->ctrl_clksel;
200 	cdns_wdt_writereg(wdt, CDNS_WDT_CCR_OFFSET, data);
201 	data = CDNS_WDT_ZMR_WDEN_MASK | CDNS_WDT_ZMR_RSTLEN_16 |
202 	       CDNS_WDT_ZMR_ZKEY_VAL;
203 
204 	/* Reset on timeout if specified in device tree. */
205 	if (wdt->rst) {
206 		data |= CDNS_WDT_ZMR_RSTEN_MASK;
207 		data &= ~CDNS_WDT_ZMR_IRQEN_MASK;
208 	} else {
209 		data &= ~CDNS_WDT_ZMR_RSTEN_MASK;
210 		data |= CDNS_WDT_ZMR_IRQEN_MASK;
211 	}
212 	cdns_wdt_writereg(wdt, CDNS_WDT_ZMR_OFFSET, data);
213 	cdns_wdt_writereg(wdt, CDNS_WDT_RESTART_OFFSET,
214 			  CDNS_WDT_RESTART_KEY);
215 	spin_unlock(&wdt->io_lock);
216 
217 	return 0;
218 }
219 
220 /**
221  * cdns_wdt_settimeout - Set a new timeout value for the watchdog device.
222  *
223  * @wdd: watchdog device
224  * @new_time: new timeout value that needs to be set
225  * Return: 0 on success
226  *
227  * Update the watchdog_device timeout with new value which is used when
228  * cdns_wdt_start is called.
229  */
230 static int cdns_wdt_settimeout(struct watchdog_device *wdd,
231 			       unsigned int new_time)
232 {
233 	wdd->timeout = new_time;
234 
235 	return cdns_wdt_start(wdd);
236 }
237 
238 /**
239  * cdns_wdt_irq_handler - Notifies of watchdog timeout.
240  *
241  * @irq: interrupt number
242  * @dev_id: pointer to a platform device structure
243  * Return: IRQ_HANDLED
244  *
245  * The handler is invoked when the watchdog times out and a
246  * reset on timeout has not been enabled.
247  */
248 static irqreturn_t cdns_wdt_irq_handler(int irq, void *dev_id)
249 {
250 	struct platform_device *pdev = dev_id;
251 
252 	dev_info(&pdev->dev,
253 		 "Watchdog timed out. Internal reset not enabled\n");
254 
255 	return IRQ_HANDLED;
256 }
257 
258 /*
259  * Info structure used to indicate the features supported by the device
260  * to the upper layers. This is defined in watchdog.h header file.
261  */
262 static const struct watchdog_info cdns_wdt_info = {
263 	.identity	= "cdns_wdt watchdog",
264 	.options	= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
265 			  WDIOF_MAGICCLOSE,
266 };
267 
268 /* Watchdog Core Ops */
269 static const struct watchdog_ops cdns_wdt_ops = {
270 	.owner = THIS_MODULE,
271 	.start = cdns_wdt_start,
272 	.stop = cdns_wdt_stop,
273 	.ping = cdns_wdt_reload,
274 	.set_timeout = cdns_wdt_settimeout,
275 };
276 
277 static void cdns_clk_disable_unprepare(void *data)
278 {
279 	clk_disable_unprepare(data);
280 }
281 
282 /************************Platform Operations*****************************/
283 /**
284  * cdns_wdt_probe - Probe call for the device.
285  *
286  * @pdev: handle to the platform device structure.
287  * Return: 0 on success, negative error otherwise.
288  *
289  * It does all the memory allocation and registration for the device.
290  */
291 static int cdns_wdt_probe(struct platform_device *pdev)
292 {
293 	struct device *dev = &pdev->dev;
294 	int ret, irq;
295 	unsigned long clock_f;
296 	struct cdns_wdt *wdt;
297 	struct watchdog_device *cdns_wdt_device;
298 
299 	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
300 	if (!wdt)
301 		return -ENOMEM;
302 
303 	cdns_wdt_device = &wdt->cdns_wdt_device;
304 	cdns_wdt_device->info = &cdns_wdt_info;
305 	cdns_wdt_device->ops = &cdns_wdt_ops;
306 	cdns_wdt_device->timeout = CDNS_WDT_DEFAULT_TIMEOUT;
307 	cdns_wdt_device->min_timeout = CDNS_WDT_MIN_TIMEOUT;
308 	cdns_wdt_device->max_timeout = CDNS_WDT_MAX_TIMEOUT;
309 
310 	wdt->regs = devm_platform_ioremap_resource(pdev, 0);
311 	if (IS_ERR(wdt->regs))
312 		return PTR_ERR(wdt->regs);
313 
314 	/* Register the interrupt */
315 	wdt->rst = of_property_read_bool(dev->of_node, "reset-on-timeout");
316 	irq = platform_get_irq(pdev, 0);
317 	if (!wdt->rst && irq >= 0) {
318 		ret = devm_request_irq(dev, irq, cdns_wdt_irq_handler, 0,
319 				       pdev->name, pdev);
320 		if (ret) {
321 			dev_err(dev,
322 				"cannot register interrupt handler err=%d\n",
323 				ret);
324 			return ret;
325 		}
326 	}
327 
328 	/* Initialize the members of cdns_wdt structure */
329 	cdns_wdt_device->parent = dev;
330 
331 	watchdog_init_timeout(cdns_wdt_device, wdt_timeout, dev);
332 	watchdog_set_nowayout(cdns_wdt_device, nowayout);
333 	watchdog_stop_on_reboot(cdns_wdt_device);
334 	watchdog_set_drvdata(cdns_wdt_device, wdt);
335 
336 	wdt->clk = devm_clk_get(dev, NULL);
337 	if (IS_ERR(wdt->clk)) {
338 		ret = PTR_ERR(wdt->clk);
339 		if (ret != -EPROBE_DEFER)
340 			dev_err(dev, "input clock not found\n");
341 		return ret;
342 	}
343 
344 	ret = clk_prepare_enable(wdt->clk);
345 	if (ret) {
346 		dev_err(dev, "unable to enable clock\n");
347 		return ret;
348 	}
349 	ret = devm_add_action_or_reset(dev, cdns_clk_disable_unprepare,
350 				       wdt->clk);
351 	if (ret)
352 		return ret;
353 
354 	clock_f = clk_get_rate(wdt->clk);
355 	if (clock_f <= CDNS_WDT_CLK_75MHZ) {
356 		wdt->prescaler = CDNS_WDT_PRESCALE_512;
357 		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_512;
358 	} else {
359 		wdt->prescaler = CDNS_WDT_PRESCALE_4096;
360 		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_4096;
361 	}
362 
363 	spin_lock_init(&wdt->io_lock);
364 
365 	watchdog_stop_on_reboot(cdns_wdt_device);
366 	watchdog_stop_on_unregister(cdns_wdt_device);
367 	ret = devm_watchdog_register_device(dev, cdns_wdt_device);
368 	if (ret)
369 		return ret;
370 	platform_set_drvdata(pdev, wdt);
371 
372 	dev_info(dev, "Xilinx Watchdog Timer with timeout %ds%s\n",
373 		 cdns_wdt_device->timeout, nowayout ? ", nowayout" : "");
374 
375 	return 0;
376 }
377 
378 /**
379  * cdns_wdt_suspend - Stop the device.
380  *
381  * @dev: handle to the device structure.
382  * Return: 0 always.
383  */
384 static int __maybe_unused cdns_wdt_suspend(struct device *dev)
385 {
386 	struct cdns_wdt *wdt = dev_get_drvdata(dev);
387 
388 	if (watchdog_active(&wdt->cdns_wdt_device)) {
389 		cdns_wdt_stop(&wdt->cdns_wdt_device);
390 		clk_disable_unprepare(wdt->clk);
391 	}
392 
393 	return 0;
394 }
395 
396 /**
397  * cdns_wdt_resume - Resume the device.
398  *
399  * @dev: handle to the device structure.
400  * Return: 0 on success, errno otherwise.
401  */
402 static int __maybe_unused cdns_wdt_resume(struct device *dev)
403 {
404 	int ret;
405 	struct cdns_wdt *wdt = dev_get_drvdata(dev);
406 
407 	if (watchdog_active(&wdt->cdns_wdt_device)) {
408 		ret = clk_prepare_enable(wdt->clk);
409 		if (ret) {
410 			dev_err(dev, "unable to enable clock\n");
411 			return ret;
412 		}
413 		cdns_wdt_start(&wdt->cdns_wdt_device);
414 	}
415 
416 	return 0;
417 }
418 
419 static SIMPLE_DEV_PM_OPS(cdns_wdt_pm_ops, cdns_wdt_suspend, cdns_wdt_resume);
420 
421 static const struct of_device_id cdns_wdt_of_match[] = {
422 	{ .compatible = "cdns,wdt-r1p2", },
423 	{ /* end of table */ }
424 };
425 MODULE_DEVICE_TABLE(of, cdns_wdt_of_match);
426 
427 /* Driver Structure */
428 static struct platform_driver cdns_wdt_driver = {
429 	.probe		= cdns_wdt_probe,
430 	.driver		= {
431 		.name	= "cdns-wdt",
432 		.of_match_table = cdns_wdt_of_match,
433 		.pm	= &cdns_wdt_pm_ops,
434 	},
435 };
436 
437 module_platform_driver(cdns_wdt_driver);
438 
439 MODULE_AUTHOR("Xilinx, Inc.");
440 MODULE_DESCRIPTION("Watchdog driver for Cadence WDT");
441 MODULE_LICENSE("GPL");
442