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 */
cdns_wdt_writereg(struct cdns_wdt * wdt,u32 offset,u32 val)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 */
cdns_wdt_stop(struct watchdog_device * wdd)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 */
cdns_wdt_reload(struct watchdog_device * wdd)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 */
cdns_wdt_start(struct watchdog_device * wdd)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 */
cdns_wdt_settimeout(struct watchdog_device * wdd,unsigned int new_time)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 */
cdns_wdt_irq_handler(int irq,void * dev_id)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
cdns_clk_disable_unprepare(void * data)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 */
cdns_wdt_probe(struct platform_device * pdev)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 dev_err(dev, "input clock not found\n");
339 return PTR_ERR(wdt->clk);
340 }
341
342 ret = clk_prepare_enable(wdt->clk);
343 if (ret) {
344 dev_err(dev, "unable to enable clock\n");
345 return ret;
346 }
347 ret = devm_add_action_or_reset(dev, cdns_clk_disable_unprepare,
348 wdt->clk);
349 if (ret)
350 return ret;
351
352 clock_f = clk_get_rate(wdt->clk);
353 if (clock_f <= CDNS_WDT_CLK_75MHZ) {
354 wdt->prescaler = CDNS_WDT_PRESCALE_512;
355 wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_512;
356 } else {
357 wdt->prescaler = CDNS_WDT_PRESCALE_4096;
358 wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_4096;
359 }
360
361 spin_lock_init(&wdt->io_lock);
362
363 watchdog_stop_on_reboot(cdns_wdt_device);
364 watchdog_stop_on_unregister(cdns_wdt_device);
365 ret = devm_watchdog_register_device(dev, cdns_wdt_device);
366 if (ret)
367 return ret;
368 platform_set_drvdata(pdev, wdt);
369
370 dev_info(dev, "Xilinx Watchdog Timer at %p with timeout %ds%s\n",
371 wdt->regs, cdns_wdt_device->timeout,
372 nowayout ? ", nowayout" : "");
373
374 return 0;
375 }
376
377 /**
378 * cdns_wdt_suspend - Stop the device.
379 *
380 * @dev: handle to the device structure.
381 * Return: 0 always.
382 */
cdns_wdt_suspend(struct device * dev)383 static int __maybe_unused cdns_wdt_suspend(struct device *dev)
384 {
385 struct cdns_wdt *wdt = dev_get_drvdata(dev);
386
387 if (watchdog_active(&wdt->cdns_wdt_device)) {
388 cdns_wdt_stop(&wdt->cdns_wdt_device);
389 clk_disable_unprepare(wdt->clk);
390 }
391
392 return 0;
393 }
394
395 /**
396 * cdns_wdt_resume - Resume the device.
397 *
398 * @dev: handle to the device structure.
399 * Return: 0 on success, errno otherwise.
400 */
cdns_wdt_resume(struct device * dev)401 static int __maybe_unused cdns_wdt_resume(struct device *dev)
402 {
403 int ret;
404 struct cdns_wdt *wdt = dev_get_drvdata(dev);
405
406 if (watchdog_active(&wdt->cdns_wdt_device)) {
407 ret = clk_prepare_enable(wdt->clk);
408 if (ret) {
409 dev_err(dev, "unable to enable clock\n");
410 return ret;
411 }
412 cdns_wdt_start(&wdt->cdns_wdt_device);
413 }
414
415 return 0;
416 }
417
418 static SIMPLE_DEV_PM_OPS(cdns_wdt_pm_ops, cdns_wdt_suspend, cdns_wdt_resume);
419
420 static const struct of_device_id cdns_wdt_of_match[] = {
421 { .compatible = "cdns,wdt-r1p2", },
422 { /* end of table */ }
423 };
424 MODULE_DEVICE_TABLE(of, cdns_wdt_of_match);
425
426 /* Driver Structure */
427 static struct platform_driver cdns_wdt_driver = {
428 .probe = cdns_wdt_probe,
429 .driver = {
430 .name = "cdns-wdt",
431 .of_match_table = cdns_wdt_of_match,
432 .pm = &cdns_wdt_pm_ops,
433 },
434 };
435
436 module_platform_driver(cdns_wdt_driver);
437
438 MODULE_AUTHOR("Xilinx, Inc.");
439 MODULE_DESCRIPTION("Watchdog driver for Cadence WDT");
440 MODULE_LICENSE("GPL");
441
