1 /*
2  * Driver for Atmel SAMA5D4 Watchdog Timer
3  *
4  * Copyright (C) 2015 Atmel Corporation
5  *
6  * Licensed under GPLv2.
7  */
8 
9 #include <linux/delay.h>
10 #include <linux/interrupt.h>
11 #include <linux/io.h>
12 #include <linux/kernel.h>
13 #include <linux/module.h>
14 #include <linux/of.h>
15 #include <linux/of_irq.h>
16 #include <linux/platform_device.h>
17 #include <linux/reboot.h>
18 #include <linux/watchdog.h>
19 
20 #include "at91sam9_wdt.h"
21 
22 /* minimum and maximum watchdog timeout, in seconds */
23 #define MIN_WDT_TIMEOUT		1
24 #define MAX_WDT_TIMEOUT		16
25 #define WDT_DEFAULT_TIMEOUT	MAX_WDT_TIMEOUT
26 
27 #define WDT_SEC2TICKS(s)	((s) ? (((s) << 8) - 1) : 0)
28 
29 struct sama5d4_wdt {
30 	struct watchdog_device	wdd;
31 	void __iomem		*reg_base;
32 	u32			mr;
33 	unsigned long		last_ping;
34 };
35 
36 static int wdt_timeout;
37 static bool nowayout = WATCHDOG_NOWAYOUT;
38 
39 module_param(wdt_timeout, int, 0);
40 MODULE_PARM_DESC(wdt_timeout,
41 	"Watchdog timeout in seconds. (default = "
42 	__MODULE_STRING(WDT_DEFAULT_TIMEOUT) ")");
43 
44 module_param(nowayout, bool, 0);
45 MODULE_PARM_DESC(nowayout,
46 	"Watchdog cannot be stopped once started (default="
47 	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
48 
49 #define wdt_enabled (!(wdt->mr & AT91_WDT_WDDIS))
50 
51 #define wdt_read(wdt, field) \
52 	readl_relaxed((wdt)->reg_base + (field))
53 
54 /* 4 slow clock periods is 4/32768 = 122.07µs*/
55 #define WDT_DELAY	usecs_to_jiffies(123)
56 
57 static void wdt_write(struct sama5d4_wdt *wdt, u32 field, u32 val)
58 {
59 	/*
60 	 * WDT_CR and WDT_MR must not be modified within three slow clock
61 	 * periods following a restart of the watchdog performed by a write
62 	 * access in WDT_CR.
63 	 */
64 	while (time_before(jiffies, wdt->last_ping + WDT_DELAY))
65 		usleep_range(30, 125);
66 	writel_relaxed(val, wdt->reg_base + field);
67 	wdt->last_ping = jiffies;
68 }
69 
70 static void wdt_write_nosleep(struct sama5d4_wdt *wdt, u32 field, u32 val)
71 {
72 	if (time_before(jiffies, wdt->last_ping + WDT_DELAY))
73 		udelay(123);
74 	writel_relaxed(val, wdt->reg_base + field);
75 	wdt->last_ping = jiffies;
76 }
77 
78 static int sama5d4_wdt_start(struct watchdog_device *wdd)
79 {
80 	struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
81 
82 	wdt->mr &= ~AT91_WDT_WDDIS;
83 	wdt_write(wdt, AT91_WDT_MR, wdt->mr);
84 
85 	return 0;
86 }
87 
88 static int sama5d4_wdt_stop(struct watchdog_device *wdd)
89 {
90 	struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
91 
92 	wdt->mr |= AT91_WDT_WDDIS;
93 	wdt_write(wdt, AT91_WDT_MR, wdt->mr);
94 
95 	return 0;
96 }
97 
98 static int sama5d4_wdt_ping(struct watchdog_device *wdd)
99 {
100 	struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
101 
102 	wdt_write(wdt, AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
103 
104 	return 0;
105 }
106 
107 static int sama5d4_wdt_set_timeout(struct watchdog_device *wdd,
108 				 unsigned int timeout)
109 {
110 	struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
111 	u32 value = WDT_SEC2TICKS(timeout);
112 
113 	wdt->mr &= ~AT91_WDT_WDV;
114 	wdt->mr &= ~AT91_WDT_WDD;
115 	wdt->mr |= AT91_WDT_SET_WDV(value);
116 	wdt->mr |= AT91_WDT_SET_WDD(value);
117 
118 	/*
119 	 * WDDIS has to be 0 when updating WDD/WDV. The datasheet states: When
120 	 * setting the WDDIS bit, and while it is set, the fields WDV and WDD
121 	 * must not be modified.
122 	 * If the watchdog is enabled, then the timeout can be updated. Else,
123 	 * wait that the user enables it.
124 	 */
125 	if (wdt_enabled)
126 		wdt_write(wdt, AT91_WDT_MR, wdt->mr & ~AT91_WDT_WDDIS);
127 
128 	wdd->timeout = timeout;
129 
130 	return 0;
131 }
132 
133 static const struct watchdog_info sama5d4_wdt_info = {
134 	.options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
135 	.identity = "Atmel SAMA5D4 Watchdog",
136 };
137 
138 static const struct watchdog_ops sama5d4_wdt_ops = {
139 	.owner = THIS_MODULE,
140 	.start = sama5d4_wdt_start,
141 	.stop = sama5d4_wdt_stop,
142 	.ping = sama5d4_wdt_ping,
143 	.set_timeout = sama5d4_wdt_set_timeout,
144 };
145 
146 static irqreturn_t sama5d4_wdt_irq_handler(int irq, void *dev_id)
147 {
148 	struct sama5d4_wdt *wdt = platform_get_drvdata(dev_id);
149 
150 	if (wdt_read(wdt, AT91_WDT_SR)) {
151 		pr_crit("Atmel Watchdog Software Reset\n");
152 		emergency_restart();
153 		pr_crit("Reboot didn't succeed\n");
154 	}
155 
156 	return IRQ_HANDLED;
157 }
158 
159 static int of_sama5d4_wdt_init(struct device_node *np, struct sama5d4_wdt *wdt)
160 {
161 	const char *tmp;
162 
163 	wdt->mr = AT91_WDT_WDDIS;
164 
165 	if (!of_property_read_string(np, "atmel,watchdog-type", &tmp) &&
166 	    !strcmp(tmp, "software"))
167 		wdt->mr |= AT91_WDT_WDFIEN;
168 	else
169 		wdt->mr |= AT91_WDT_WDRSTEN;
170 
171 	if (of_property_read_bool(np, "atmel,idle-halt"))
172 		wdt->mr |= AT91_WDT_WDIDLEHLT;
173 
174 	if (of_property_read_bool(np, "atmel,dbg-halt"))
175 		wdt->mr |= AT91_WDT_WDDBGHLT;
176 
177 	return 0;
178 }
179 
180 static int sama5d4_wdt_init(struct sama5d4_wdt *wdt)
181 {
182 	u32 reg;
183 	/*
184 	 * When booting and resuming, the bootloader may have changed the
185 	 * watchdog configuration.
186 	 * If the watchdog is already running, we can safely update it.
187 	 * Else, we have to disable it properly.
188 	 */
189 	if (wdt_enabled) {
190 		wdt_write_nosleep(wdt, AT91_WDT_MR, wdt->mr);
191 	} else {
192 		reg = wdt_read(wdt, AT91_WDT_MR);
193 		if (!(reg & AT91_WDT_WDDIS))
194 			wdt_write_nosleep(wdt, AT91_WDT_MR,
195 					  reg | AT91_WDT_WDDIS);
196 	}
197 	return 0;
198 }
199 
200 static int sama5d4_wdt_probe(struct platform_device *pdev)
201 {
202 	struct device *dev = &pdev->dev;
203 	struct watchdog_device *wdd;
204 	struct sama5d4_wdt *wdt;
205 	void __iomem *regs;
206 	u32 irq = 0;
207 	u32 timeout;
208 	int ret;
209 
210 	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
211 	if (!wdt)
212 		return -ENOMEM;
213 
214 	wdd = &wdt->wdd;
215 	wdd->timeout = WDT_DEFAULT_TIMEOUT;
216 	wdd->info = &sama5d4_wdt_info;
217 	wdd->ops = &sama5d4_wdt_ops;
218 	wdd->min_timeout = MIN_WDT_TIMEOUT;
219 	wdd->max_timeout = MAX_WDT_TIMEOUT;
220 	wdt->last_ping = jiffies;
221 
222 	watchdog_set_drvdata(wdd, wdt);
223 
224 	regs = devm_platform_ioremap_resource(pdev, 0);
225 	if (IS_ERR(regs))
226 		return PTR_ERR(regs);
227 
228 	wdt->reg_base = regs;
229 
230 	irq = irq_of_parse_and_map(dev->of_node, 0);
231 	if (!irq)
232 		dev_warn(dev, "failed to get IRQ from DT\n");
233 
234 	ret = of_sama5d4_wdt_init(dev->of_node, wdt);
235 	if (ret)
236 		return ret;
237 
238 	if ((wdt->mr & AT91_WDT_WDFIEN) && irq) {
239 		ret = devm_request_irq(dev, irq, sama5d4_wdt_irq_handler,
240 				       IRQF_SHARED | IRQF_IRQPOLL |
241 				       IRQF_NO_SUSPEND, pdev->name, pdev);
242 		if (ret) {
243 			dev_err(dev, "cannot register interrupt handler\n");
244 			return ret;
245 		}
246 	}
247 
248 	watchdog_init_timeout(wdd, wdt_timeout, dev);
249 
250 	timeout = WDT_SEC2TICKS(wdd->timeout);
251 
252 	wdt->mr |= AT91_WDT_SET_WDD(timeout);
253 	wdt->mr |= AT91_WDT_SET_WDV(timeout);
254 
255 	ret = sama5d4_wdt_init(wdt);
256 	if (ret)
257 		return ret;
258 
259 	watchdog_set_nowayout(wdd, nowayout);
260 
261 	watchdog_stop_on_unregister(wdd);
262 	ret = devm_watchdog_register_device(dev, wdd);
263 	if (ret) {
264 		dev_err(dev, "failed to register watchdog device\n");
265 		return ret;
266 	}
267 
268 	platform_set_drvdata(pdev, wdt);
269 
270 	dev_info(dev, "initialized (timeout = %d sec, nowayout = %d)\n",
271 		 wdd->timeout, nowayout);
272 
273 	return 0;
274 }
275 
276 static const struct of_device_id sama5d4_wdt_of_match[] = {
277 	{ .compatible = "atmel,sama5d4-wdt", },
278 	{ }
279 };
280 MODULE_DEVICE_TABLE(of, sama5d4_wdt_of_match);
281 
282 #ifdef CONFIG_PM_SLEEP
283 static int sama5d4_wdt_resume(struct device *dev)
284 {
285 	struct sama5d4_wdt *wdt = dev_get_drvdata(dev);
286 
287 	/*
288 	 * FIXME: writing MR also pings the watchdog which may not be desired.
289 	 * This should only be done when the registers are lost on suspend but
290 	 * there is no way to get this information right now.
291 	 */
292 	sama5d4_wdt_init(wdt);
293 
294 	return 0;
295 }
296 #endif
297 
298 static SIMPLE_DEV_PM_OPS(sama5d4_wdt_pm_ops, NULL,
299 			 sama5d4_wdt_resume);
300 
301 static struct platform_driver sama5d4_wdt_driver = {
302 	.probe		= sama5d4_wdt_probe,
303 	.driver		= {
304 		.name	= "sama5d4_wdt",
305 		.pm	= &sama5d4_wdt_pm_ops,
306 		.of_match_table = sama5d4_wdt_of_match,
307 	}
308 };
309 module_platform_driver(sama5d4_wdt_driver);
310 
311 MODULE_AUTHOR("Atmel Corporation");
312 MODULE_DESCRIPTION("Atmel SAMA5D4 Watchdog Timer driver");
313 MODULE_LICENSE("GPL v2");
314