1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Watchdog driver for Marvell Armada 37xx SoCs
4  *
5  * Author: Marek Behún <kabel@kernel.org>
6  */
7 
8 #include <linux/clk.h>
9 #include <linux/err.h>
10 #include <linux/interrupt.h>
11 #include <linux/io.h>
12 #include <linux/kernel.h>
13 #include <linux/mfd/syscon.h>
14 #include <linux/module.h>
15 #include <linux/moduleparam.h>
16 #include <linux/of.h>
17 #include <linux/of_device.h>
18 #include <linux/platform_device.h>
19 #include <linux/regmap.h>
20 #include <linux/types.h>
21 #include <linux/watchdog.h>
22 
23 /*
24  * There are four counters that can be used for watchdog on Armada 37xx.
25  * The addresses for counter control registers are register base plus ID*0x10,
26  * where ID is 0, 1, 2 or 3.
27  *
28  * In this driver we use IDs 0 and 1. Counter ID 1 is used as watchdog counter,
29  * while counter ID 0 is used to implement pinging the watchdog: counter ID 1 is
30  * set to restart counting from initial value on counter ID 0 end count event.
31  * Pinging is done by forcing immediate end count event on counter ID 0.
32  * If only one counter was used, pinging would have to be implemented by
33  * disabling and enabling the counter, leaving the system in a vulnerable state
34  * for a (really) short period of time.
35  *
36  * Counters ID 2 and 3 are enabled by default even before U-Boot loads,
37  * therefore this driver does not provide a way to use them, eg. by setting a
38  * property in device tree.
39  */
40 
41 #define CNTR_ID_RETRIGGER		0
42 #define CNTR_ID_WDOG			1
43 
44 /* relative to cpu_misc */
45 #define WDT_TIMER_SELECT		0x64
46 #define WDT_TIMER_SELECT_MASK		0xf
47 #define WDT_TIMER_SELECT_VAL		BIT(CNTR_ID_WDOG)
48 
49 /* relative to reg */
50 #define CNTR_CTRL(id)			((id) * 0x10)
51 #define CNTR_CTRL_ENABLE		0x0001
52 #define CNTR_CTRL_ACTIVE		0x0002
53 #define CNTR_CTRL_MODE_MASK		0x000c
54 #define CNTR_CTRL_MODE_ONESHOT		0x0000
55 #define CNTR_CTRL_MODE_HWSIG		0x000c
56 #define CNTR_CTRL_TRIG_SRC_MASK		0x00f0
57 #define CNTR_CTRL_TRIG_SRC_PREV_CNTR	0x0050
58 #define CNTR_CTRL_PRESCALE_MASK		0xff00
59 #define CNTR_CTRL_PRESCALE_MIN		2
60 #define CNTR_CTRL_PRESCALE_SHIFT	8
61 
62 #define CNTR_COUNT_LOW(id)		(CNTR_CTRL(id) + 0x4)
63 #define CNTR_COUNT_HIGH(id)		(CNTR_CTRL(id) + 0x8)
64 
65 #define WATCHDOG_TIMEOUT		120
66 
67 static unsigned int timeout;
68 module_param(timeout, int, 0);
69 MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds");
70 
71 static bool nowayout = WATCHDOG_NOWAYOUT;
72 module_param(nowayout, bool, 0);
73 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
74 			   __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
75 
76 struct armada_37xx_watchdog {
77 	struct watchdog_device wdt;
78 	struct regmap *cpu_misc;
79 	void __iomem *reg;
80 	u64 timeout; /* in clock ticks */
81 	unsigned long clk_rate;
82 	struct clk *clk;
83 };
84 
85 static u64 get_counter_value(struct armada_37xx_watchdog *dev, int id)
86 {
87 	u64 val;
88 
89 	/*
90 	 * when low is read, high is latched into flip-flops so that it can be
91 	 * read consistently without using software debouncing
92 	 */
93 	val = readl(dev->reg + CNTR_COUNT_LOW(id));
94 	val |= ((u64)readl(dev->reg + CNTR_COUNT_HIGH(id))) << 32;
95 
96 	return val;
97 }
98 
99 static void set_counter_value(struct armada_37xx_watchdog *dev, int id, u64 val)
100 {
101 	writel(val & 0xffffffff, dev->reg + CNTR_COUNT_LOW(id));
102 	writel(val >> 32, dev->reg + CNTR_COUNT_HIGH(id));
103 }
104 
105 static void counter_enable(struct armada_37xx_watchdog *dev, int id)
106 {
107 	u32 reg;
108 
109 	reg = readl(dev->reg + CNTR_CTRL(id));
110 	reg |= CNTR_CTRL_ENABLE;
111 	writel(reg, dev->reg + CNTR_CTRL(id));
112 }
113 
114 static void counter_disable(struct armada_37xx_watchdog *dev, int id)
115 {
116 	u32 reg;
117 
118 	reg = readl(dev->reg + CNTR_CTRL(id));
119 	reg &= ~CNTR_CTRL_ENABLE;
120 	writel(reg, dev->reg + CNTR_CTRL(id));
121 }
122 
123 static void init_counter(struct armada_37xx_watchdog *dev, int id, u32 mode,
124 			 u32 trig_src)
125 {
126 	u32 reg;
127 
128 	reg = readl(dev->reg + CNTR_CTRL(id));
129 
130 	reg &= ~(CNTR_CTRL_MODE_MASK | CNTR_CTRL_PRESCALE_MASK |
131 		 CNTR_CTRL_TRIG_SRC_MASK);
132 
133 	/* set mode */
134 	reg |= mode & CNTR_CTRL_MODE_MASK;
135 
136 	/* set prescaler to the min value */
137 	reg |= CNTR_CTRL_PRESCALE_MIN << CNTR_CTRL_PRESCALE_SHIFT;
138 
139 	/* set trigger source */
140 	reg |= trig_src & CNTR_CTRL_TRIG_SRC_MASK;
141 
142 	writel(reg, dev->reg + CNTR_CTRL(id));
143 }
144 
145 static int armada_37xx_wdt_ping(struct watchdog_device *wdt)
146 {
147 	struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);
148 
149 	/* counter 1 is retriggered by forcing end count on counter 0 */
150 	counter_disable(dev, CNTR_ID_RETRIGGER);
151 	counter_enable(dev, CNTR_ID_RETRIGGER);
152 
153 	return 0;
154 }
155 
156 static unsigned int armada_37xx_wdt_get_timeleft(struct watchdog_device *wdt)
157 {
158 	struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);
159 	u64 res;
160 
161 	res = get_counter_value(dev, CNTR_ID_WDOG) * CNTR_CTRL_PRESCALE_MIN;
162 	do_div(res, dev->clk_rate);
163 
164 	return res;
165 }
166 
167 static int armada_37xx_wdt_set_timeout(struct watchdog_device *wdt,
168 				       unsigned int timeout)
169 {
170 	struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);
171 
172 	wdt->timeout = timeout;
173 
174 	/*
175 	 * Compute the timeout in clock rate. We use smallest possible
176 	 * prescaler, which divides the clock rate by 2
177 	 * (CNTR_CTRL_PRESCALE_MIN).
178 	 */
179 	dev->timeout = (u64)dev->clk_rate * timeout;
180 	do_div(dev->timeout, CNTR_CTRL_PRESCALE_MIN);
181 
182 	return 0;
183 }
184 
185 static bool armada_37xx_wdt_is_running(struct armada_37xx_watchdog *dev)
186 {
187 	u32 reg;
188 
189 	regmap_read(dev->cpu_misc, WDT_TIMER_SELECT, &reg);
190 	if ((reg & WDT_TIMER_SELECT_MASK) != WDT_TIMER_SELECT_VAL)
191 		return false;
192 
193 	reg = readl(dev->reg + CNTR_CTRL(CNTR_ID_WDOG));
194 	return !!(reg & CNTR_CTRL_ACTIVE);
195 }
196 
197 static int armada_37xx_wdt_start(struct watchdog_device *wdt)
198 {
199 	struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);
200 
201 	/* select counter 1 as watchdog counter */
202 	regmap_write(dev->cpu_misc, WDT_TIMER_SELECT, WDT_TIMER_SELECT_VAL);
203 
204 	/* init counter 0 as retrigger counter for counter 1 */
205 	init_counter(dev, CNTR_ID_RETRIGGER, CNTR_CTRL_MODE_ONESHOT, 0);
206 	set_counter_value(dev, CNTR_ID_RETRIGGER, 0);
207 
208 	/* init counter 1 to be retriggerable by counter 0 end count */
209 	init_counter(dev, CNTR_ID_WDOG, CNTR_CTRL_MODE_HWSIG,
210 		     CNTR_CTRL_TRIG_SRC_PREV_CNTR);
211 	set_counter_value(dev, CNTR_ID_WDOG, dev->timeout);
212 
213 	/* enable counter 1 */
214 	counter_enable(dev, CNTR_ID_WDOG);
215 
216 	/* start counter 1 by forcing immediate end count on counter 0 */
217 	counter_enable(dev, CNTR_ID_RETRIGGER);
218 
219 	return 0;
220 }
221 
222 static int armada_37xx_wdt_stop(struct watchdog_device *wdt)
223 {
224 	struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);
225 
226 	counter_disable(dev, CNTR_ID_WDOG);
227 	counter_disable(dev, CNTR_ID_RETRIGGER);
228 	regmap_write(dev->cpu_misc, WDT_TIMER_SELECT, 0);
229 
230 	return 0;
231 }
232 
233 static const struct watchdog_info armada_37xx_wdt_info = {
234 	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
235 	.identity = "Armada 37xx Watchdog",
236 };
237 
238 static const struct watchdog_ops armada_37xx_wdt_ops = {
239 	.owner = THIS_MODULE,
240 	.start = armada_37xx_wdt_start,
241 	.stop = armada_37xx_wdt_stop,
242 	.ping = armada_37xx_wdt_ping,
243 	.set_timeout = armada_37xx_wdt_set_timeout,
244 	.get_timeleft = armada_37xx_wdt_get_timeleft,
245 };
246 
247 static void armada_clk_disable_unprepare(void *data)
248 {
249 	clk_disable_unprepare(data);
250 }
251 
252 static int armada_37xx_wdt_probe(struct platform_device *pdev)
253 {
254 	struct armada_37xx_watchdog *dev;
255 	struct resource *res;
256 	struct regmap *regmap;
257 	int ret;
258 
259 	dev = devm_kzalloc(&pdev->dev, sizeof(struct armada_37xx_watchdog),
260 			   GFP_KERNEL);
261 	if (!dev)
262 		return -ENOMEM;
263 
264 	dev->wdt.info = &armada_37xx_wdt_info;
265 	dev->wdt.ops = &armada_37xx_wdt_ops;
266 
267 	regmap = syscon_regmap_lookup_by_phandle(pdev->dev.of_node,
268 						 "marvell,system-controller");
269 	if (IS_ERR(regmap))
270 		return PTR_ERR(regmap);
271 	dev->cpu_misc = regmap;
272 
273 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
274 	if (!res)
275 		return -ENODEV;
276 	dev->reg = devm_ioremap(&pdev->dev, res->start, resource_size(res));
277 	if (!dev->reg)
278 		return -ENOMEM;
279 
280 	/* init clock */
281 	dev->clk = devm_clk_get(&pdev->dev, NULL);
282 	if (IS_ERR(dev->clk))
283 		return PTR_ERR(dev->clk);
284 
285 	ret = clk_prepare_enable(dev->clk);
286 	if (ret)
287 		return ret;
288 	ret = devm_add_action_or_reset(&pdev->dev,
289 				       armada_clk_disable_unprepare, dev->clk);
290 	if (ret)
291 		return ret;
292 
293 	dev->clk_rate = clk_get_rate(dev->clk);
294 	if (!dev->clk_rate)
295 		return -EINVAL;
296 
297 	/*
298 	 * Since the timeout in seconds is given as 32 bit unsigned int, and
299 	 * the counters hold 64 bit values, even after multiplication by clock
300 	 * rate the counter can hold timeout of UINT_MAX seconds.
301 	 */
302 	dev->wdt.min_timeout = 1;
303 	dev->wdt.max_timeout = UINT_MAX;
304 	dev->wdt.parent = &pdev->dev;
305 
306 	/* default value, possibly override by module parameter or dtb */
307 	dev->wdt.timeout = WATCHDOG_TIMEOUT;
308 	watchdog_init_timeout(&dev->wdt, timeout, &pdev->dev);
309 
310 	platform_set_drvdata(pdev, &dev->wdt);
311 	watchdog_set_drvdata(&dev->wdt, dev);
312 
313 	armada_37xx_wdt_set_timeout(&dev->wdt, dev->wdt.timeout);
314 
315 	if (armada_37xx_wdt_is_running(dev))
316 		set_bit(WDOG_HW_RUNNING, &dev->wdt.status);
317 
318 	watchdog_set_nowayout(&dev->wdt, nowayout);
319 	watchdog_stop_on_reboot(&dev->wdt);
320 	ret = devm_watchdog_register_device(&pdev->dev, &dev->wdt);
321 	if (ret)
322 		return ret;
323 
324 	dev_info(&pdev->dev, "Initial timeout %d sec%s\n",
325 		 dev->wdt.timeout, nowayout ? ", nowayout" : "");
326 
327 	return 0;
328 }
329 
330 static int __maybe_unused armada_37xx_wdt_suspend(struct device *dev)
331 {
332 	struct watchdog_device *wdt = dev_get_drvdata(dev);
333 
334 	return armada_37xx_wdt_stop(wdt);
335 }
336 
337 static int __maybe_unused armada_37xx_wdt_resume(struct device *dev)
338 {
339 	struct watchdog_device *wdt = dev_get_drvdata(dev);
340 
341 	if (watchdog_active(wdt))
342 		return armada_37xx_wdt_start(wdt);
343 
344 	return 0;
345 }
346 
347 static const struct dev_pm_ops armada_37xx_wdt_dev_pm_ops = {
348 	SET_SYSTEM_SLEEP_PM_OPS(armada_37xx_wdt_suspend,
349 				armada_37xx_wdt_resume)
350 };
351 
352 #ifdef CONFIG_OF
353 static const struct of_device_id armada_37xx_wdt_match[] = {
354 	{ .compatible = "marvell,armada-3700-wdt", },
355 	{},
356 };
357 MODULE_DEVICE_TABLE(of, armada_37xx_wdt_match);
358 #endif
359 
360 static struct platform_driver armada_37xx_wdt_driver = {
361 	.probe		= armada_37xx_wdt_probe,
362 	.driver		= {
363 		.name	= "armada_37xx_wdt",
364 		.of_match_table = of_match_ptr(armada_37xx_wdt_match),
365 		.pm = &armada_37xx_wdt_dev_pm_ops,
366 	},
367 };
368 
369 module_platform_driver(armada_37xx_wdt_driver);
370 
371 MODULE_AUTHOR("Marek Behun <kabel@kernel.org>");
372 MODULE_DESCRIPTION("Armada 37xx CPU Watchdog");
373 
374 MODULE_LICENSE("GPL v2");
375 MODULE_ALIAS("platform:armada_37xx_wdt");
376