1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Driver for Atmel SAMA5D4 Watchdog Timer
4  *
5  * Copyright (C) 2015 Atmel Corporation
6  */
7 
8 #include <linux/delay.h>
9 #include <linux/interrupt.h>
10 #include <linux/io.h>
11 #include <linux/kernel.h>
12 #include <linux/module.h>
13 #include <linux/of.h>
14 #include <linux/of_irq.h>
15 #include <linux/platform_device.h>
16 #include <linux/reboot.h>
17 #include <linux/watchdog.h>
18 
19 #include "at91sam9_wdt.h"
20 
21 /* minimum and maximum watchdog timeout, in seconds */
22 #define MIN_WDT_TIMEOUT		1
23 #define MAX_WDT_TIMEOUT		16
24 #define WDT_DEFAULT_TIMEOUT	MAX_WDT_TIMEOUT
25 
26 #define WDT_SEC2TICKS(s)	((s) ? (((s) << 8) - 1) : 0)
27 
28 struct sama5d4_wdt {
29 	struct watchdog_device	wdd;
30 	void __iomem		*reg_base;
31 	u32			mr;
32 	unsigned long		last_ping;
33 };
34 
35 static int wdt_timeout;
36 static bool nowayout = WATCHDOG_NOWAYOUT;
37 
38 module_param(wdt_timeout, int, 0);
39 MODULE_PARM_DESC(wdt_timeout,
40 	"Watchdog timeout in seconds. (default = "
41 	__MODULE_STRING(WDT_DEFAULT_TIMEOUT) ")");
42 
43 module_param(nowayout, bool, 0);
44 MODULE_PARM_DESC(nowayout,
45 	"Watchdog cannot be stopped once started (default="
46 	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
47 
48 #define wdt_enabled (!(wdt->mr & AT91_WDT_WDDIS))
49 
50 #define wdt_read(wdt, field) \
51 	readl_relaxed((wdt)->reg_base + (field))
52 
53 /* 4 slow clock periods is 4/32768 = 122.07µs*/
54 #define WDT_DELAY	usecs_to_jiffies(123)
55 
56 static void wdt_write(struct sama5d4_wdt *wdt, u32 field, u32 val)
57 {
58 	/*
59 	 * WDT_CR and WDT_MR must not be modified within three slow clock
60 	 * periods following a restart of the watchdog performed by a write
61 	 * access in WDT_CR.
62 	 */
63 	while (time_before(jiffies, wdt->last_ping + WDT_DELAY))
64 		usleep_range(30, 125);
65 	writel_relaxed(val, wdt->reg_base + field);
66 	wdt->last_ping = jiffies;
67 }
68 
69 static void wdt_write_nosleep(struct sama5d4_wdt *wdt, u32 field, u32 val)
70 {
71 	if (time_before(jiffies, wdt->last_ping + WDT_DELAY))
72 		udelay(123);
73 	writel_relaxed(val, wdt->reg_base + field);
74 	wdt->last_ping = jiffies;
75 }
76 
77 static int sama5d4_wdt_start(struct watchdog_device *wdd)
78 {
79 	struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
80 
81 	wdt->mr &= ~AT91_WDT_WDDIS;
82 	wdt_write(wdt, AT91_WDT_MR, wdt->mr);
83 
84 	return 0;
85 }
86 
87 static int sama5d4_wdt_stop(struct watchdog_device *wdd)
88 {
89 	struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
90 
91 	wdt->mr |= AT91_WDT_WDDIS;
92 	wdt_write(wdt, AT91_WDT_MR, wdt->mr);
93 
94 	return 0;
95 }
96 
97 static int sama5d4_wdt_ping(struct watchdog_device *wdd)
98 {
99 	struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
100 
101 	wdt_write(wdt, AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
102 
103 	return 0;
104 }
105 
106 static int sama5d4_wdt_set_timeout(struct watchdog_device *wdd,
107 				 unsigned int timeout)
108 {
109 	struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
110 	u32 value = WDT_SEC2TICKS(timeout);
111 
112 	wdt->mr &= ~AT91_WDT_WDV;
113 	wdt->mr &= ~AT91_WDT_WDD;
114 	wdt->mr |= AT91_WDT_SET_WDV(value);
115 	wdt->mr |= AT91_WDT_SET_WDD(value);
116 
117 	/*
118 	 * WDDIS has to be 0 when updating WDD/WDV. The datasheet states: When
119 	 * setting the WDDIS bit, and while it is set, the fields WDV and WDD
120 	 * must not be modified.
121 	 * If the watchdog is enabled, then the timeout can be updated. Else,
122 	 * wait that the user enables it.
123 	 */
124 	if (wdt_enabled)
125 		wdt_write(wdt, AT91_WDT_MR, wdt->mr & ~AT91_WDT_WDDIS);
126 
127 	wdd->timeout = timeout;
128 
129 	return 0;
130 }
131 
132 static const struct watchdog_info sama5d4_wdt_info = {
133 	.options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
134 	.identity = "Atmel SAMA5D4 Watchdog",
135 };
136 
137 static const struct watchdog_ops sama5d4_wdt_ops = {
138 	.owner = THIS_MODULE,
139 	.start = sama5d4_wdt_start,
140 	.stop = sama5d4_wdt_stop,
141 	.ping = sama5d4_wdt_ping,
142 	.set_timeout = sama5d4_wdt_set_timeout,
143 };
144 
145 static irqreturn_t sama5d4_wdt_irq_handler(int irq, void *dev_id)
146 {
147 	struct sama5d4_wdt *wdt = platform_get_drvdata(dev_id);
148 
149 	if (wdt_read(wdt, AT91_WDT_SR)) {
150 		pr_crit("Atmel Watchdog Software Reset\n");
151 		emergency_restart();
152 		pr_crit("Reboot didn't succeed\n");
153 	}
154 
155 	return IRQ_HANDLED;
156 }
157 
158 static int of_sama5d4_wdt_init(struct device_node *np, struct sama5d4_wdt *wdt)
159 {
160 	const char *tmp;
161 
162 	wdt->mr = AT91_WDT_WDDIS;
163 
164 	if (!of_property_read_string(np, "atmel,watchdog-type", &tmp) &&
165 	    !strcmp(tmp, "software"))
166 		wdt->mr |= AT91_WDT_WDFIEN;
167 	else
168 		wdt->mr |= AT91_WDT_WDRSTEN;
169 
170 	if (of_property_read_bool(np, "atmel,idle-halt"))
171 		wdt->mr |= AT91_WDT_WDIDLEHLT;
172 
173 	if (of_property_read_bool(np, "atmel,dbg-halt"))
174 		wdt->mr |= AT91_WDT_WDDBGHLT;
175 
176 	return 0;
177 }
178 
179 static int sama5d4_wdt_init(struct sama5d4_wdt *wdt)
180 {
181 	u32 reg;
182 	/*
183 	 * When booting and resuming, the bootloader may have changed the
184 	 * watchdog configuration.
185 	 * If the watchdog is already running, we can safely update it.
186 	 * Else, we have to disable it properly.
187 	 */
188 	if (wdt_enabled) {
189 		wdt_write_nosleep(wdt, AT91_WDT_MR, wdt->mr);
190 	} else {
191 		reg = wdt_read(wdt, AT91_WDT_MR);
192 		if (!(reg & AT91_WDT_WDDIS))
193 			wdt_write_nosleep(wdt, AT91_WDT_MR,
194 					  reg | AT91_WDT_WDDIS);
195 	}
196 	return 0;
197 }
198 
199 static int sama5d4_wdt_probe(struct platform_device *pdev)
200 {
201 	struct device *dev = &pdev->dev;
202 	struct watchdog_device *wdd;
203 	struct sama5d4_wdt *wdt;
204 	void __iomem *regs;
205 	u32 irq = 0;
206 	u32 timeout;
207 	int ret;
208 
209 	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
210 	if (!wdt)
211 		return -ENOMEM;
212 
213 	wdd = &wdt->wdd;
214 	wdd->timeout = WDT_DEFAULT_TIMEOUT;
215 	wdd->info = &sama5d4_wdt_info;
216 	wdd->ops = &sama5d4_wdt_ops;
217 	wdd->min_timeout = MIN_WDT_TIMEOUT;
218 	wdd->max_timeout = MAX_WDT_TIMEOUT;
219 	wdt->last_ping = jiffies;
220 
221 	watchdog_set_drvdata(wdd, wdt);
222 
223 	regs = devm_platform_ioremap_resource(pdev, 0);
224 	if (IS_ERR(regs))
225 		return PTR_ERR(regs);
226 
227 	wdt->reg_base = regs;
228 
229 	irq = irq_of_parse_and_map(dev->of_node, 0);
230 	if (!irq)
231 		dev_warn(dev, "failed to get IRQ from DT\n");
232 
233 	ret = of_sama5d4_wdt_init(dev->of_node, wdt);
234 	if (ret)
235 		return ret;
236 
237 	if ((wdt->mr & AT91_WDT_WDFIEN) && irq) {
238 		ret = devm_request_irq(dev, irq, sama5d4_wdt_irq_handler,
239 				       IRQF_SHARED | IRQF_IRQPOLL |
240 				       IRQF_NO_SUSPEND, pdev->name, pdev);
241 		if (ret) {
242 			dev_err(dev, "cannot register interrupt handler\n");
243 			return ret;
244 		}
245 	}
246 
247 	watchdog_init_timeout(wdd, wdt_timeout, dev);
248 
249 	timeout = WDT_SEC2TICKS(wdd->timeout);
250 
251 	wdt->mr |= AT91_WDT_SET_WDD(timeout);
252 	wdt->mr |= AT91_WDT_SET_WDV(timeout);
253 
254 	ret = sama5d4_wdt_init(wdt);
255 	if (ret)
256 		return ret;
257 
258 	watchdog_set_nowayout(wdd, nowayout);
259 
260 	watchdog_stop_on_unregister(wdd);
261 	ret = devm_watchdog_register_device(dev, wdd);
262 	if (ret) {
263 		dev_err(dev, "failed to register watchdog device\n");
264 		return ret;
265 	}
266 
267 	platform_set_drvdata(pdev, wdt);
268 
269 	dev_info(dev, "initialized (timeout = %d sec, nowayout = %d)\n",
270 		 wdd->timeout, nowayout);
271 
272 	return 0;
273 }
274 
275 static const struct of_device_id sama5d4_wdt_of_match[] = {
276 	{ .compatible = "atmel,sama5d4-wdt", },
277 	{ }
278 };
279 MODULE_DEVICE_TABLE(of, sama5d4_wdt_of_match);
280 
281 #ifdef CONFIG_PM_SLEEP
282 static int sama5d4_wdt_resume(struct device *dev)
283 {
284 	struct sama5d4_wdt *wdt = dev_get_drvdata(dev);
285 
286 	/*
287 	 * FIXME: writing MR also pings the watchdog which may not be desired.
288 	 * This should only be done when the registers are lost on suspend but
289 	 * there is no way to get this information right now.
290 	 */
291 	sama5d4_wdt_init(wdt);
292 
293 	return 0;
294 }
295 #endif
296 
297 static SIMPLE_DEV_PM_OPS(sama5d4_wdt_pm_ops, NULL,
298 			 sama5d4_wdt_resume);
299 
300 static struct platform_driver sama5d4_wdt_driver = {
301 	.probe		= sama5d4_wdt_probe,
302 	.driver		= {
303 		.name	= "sama5d4_wdt",
304 		.pm	= &sama5d4_wdt_pm_ops,
305 		.of_match_table = sama5d4_wdt_of_match,
306 	}
307 };
308 module_platform_driver(sama5d4_wdt_driver);
309 
310 MODULE_AUTHOR("Atmel Corporation");
311 MODULE_DESCRIPTION("Atmel SAMA5D4 Watchdog Timer driver");
312 MODULE_LICENSE("GPL v2");
313