1 /*
2  * NXP LPC18xx Watchdog Timer (WDT)
3  *
4  * Copyright (c) 2015 Ariel D'Alessandro <ariel@vanguardiasur.com>
5  *
6  * This program is free software; you can redistribute it and/or modify it
7  * under the terms of the GNU General Public License version 2 as published by
8  * the Free Software Foundation.
9  *
10  * Notes
11  * -----
12  * The Watchdog consists of a fixed divide-by-4 clock pre-scaler and a 24-bit
13  * counter which decrements on every clock cycle.
14  */
15 
16 #include <linux/clk.h>
17 #include <linux/io.h>
18 #include <linux/module.h>
19 #include <linux/of.h>
20 #include <linux/platform_device.h>
21 #include <linux/watchdog.h>
22 
23 /* Registers */
24 #define LPC18XX_WDT_MOD			0x00
25 #define LPC18XX_WDT_MOD_WDEN		BIT(0)
26 #define LPC18XX_WDT_MOD_WDRESET		BIT(1)
27 
28 #define LPC18XX_WDT_TC			0x04
29 #define LPC18XX_WDT_TC_MIN		0xff
30 #define LPC18XX_WDT_TC_MAX		0xffffff
31 
32 #define LPC18XX_WDT_FEED		0x08
33 #define LPC18XX_WDT_FEED_MAGIC1		0xaa
34 #define LPC18XX_WDT_FEED_MAGIC2		0x55
35 
36 #define LPC18XX_WDT_TV			0x0c
37 
38 /* Clock pre-scaler */
39 #define LPC18XX_WDT_CLK_DIV		4
40 
41 /* Timeout values in seconds */
42 #define LPC18XX_WDT_DEF_TIMEOUT		30U
43 
44 static int heartbeat;
45 module_param(heartbeat, int, 0);
46 MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds (default="
47 		 __MODULE_STRING(LPC18XX_WDT_DEF_TIMEOUT) ")");
48 
49 static bool nowayout = WATCHDOG_NOWAYOUT;
50 module_param(nowayout, bool, 0);
51 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
52 		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
53 
54 struct lpc18xx_wdt_dev {
55 	struct watchdog_device	wdt_dev;
56 	struct clk		*reg_clk;
57 	struct clk		*wdt_clk;
58 	unsigned long		clk_rate;
59 	void __iomem		*base;
60 	struct timer_list	timer;
61 	spinlock_t		lock;
62 };
63 
64 static int lpc18xx_wdt_feed(struct watchdog_device *wdt_dev)
65 {
66 	struct lpc18xx_wdt_dev *lpc18xx_wdt = watchdog_get_drvdata(wdt_dev);
67 	unsigned long flags;
68 
69 	/*
70 	 * An abort condition will occur if an interrupt happens during the feed
71 	 * sequence.
72 	 */
73 	spin_lock_irqsave(&lpc18xx_wdt->lock, flags);
74 	writel(LPC18XX_WDT_FEED_MAGIC1, lpc18xx_wdt->base + LPC18XX_WDT_FEED);
75 	writel(LPC18XX_WDT_FEED_MAGIC2, lpc18xx_wdt->base + LPC18XX_WDT_FEED);
76 	spin_unlock_irqrestore(&lpc18xx_wdt->lock, flags);
77 
78 	return 0;
79 }
80 
81 static void lpc18xx_wdt_timer_feed(struct timer_list *t)
82 {
83 	struct lpc18xx_wdt_dev *lpc18xx_wdt = from_timer(lpc18xx_wdt, t, timer);
84 	struct watchdog_device *wdt_dev = &lpc18xx_wdt->wdt_dev;
85 
86 	lpc18xx_wdt_feed(wdt_dev);
87 
88 	/* Use safe value (1/2 of real timeout) */
89 	mod_timer(&lpc18xx_wdt->timer, jiffies +
90 		  msecs_to_jiffies((wdt_dev->timeout * MSEC_PER_SEC) / 2));
91 }
92 
93 /*
94  * Since LPC18xx Watchdog cannot be disabled in hardware, we must keep feeding
95  * it with a timer until userspace watchdog software takes over.
96  */
97 static int lpc18xx_wdt_stop(struct watchdog_device *wdt_dev)
98 {
99 	struct lpc18xx_wdt_dev *lpc18xx_wdt = watchdog_get_drvdata(wdt_dev);
100 
101 	lpc18xx_wdt_timer_feed(&lpc18xx_wdt->timer);
102 
103 	return 0;
104 }
105 
106 static void __lpc18xx_wdt_set_timeout(struct lpc18xx_wdt_dev *lpc18xx_wdt)
107 {
108 	unsigned int val;
109 
110 	val = DIV_ROUND_UP(lpc18xx_wdt->wdt_dev.timeout * lpc18xx_wdt->clk_rate,
111 			   LPC18XX_WDT_CLK_DIV);
112 	writel(val, lpc18xx_wdt->base + LPC18XX_WDT_TC);
113 }
114 
115 static int lpc18xx_wdt_set_timeout(struct watchdog_device *wdt_dev,
116 				   unsigned int new_timeout)
117 {
118 	struct lpc18xx_wdt_dev *lpc18xx_wdt = watchdog_get_drvdata(wdt_dev);
119 
120 	lpc18xx_wdt->wdt_dev.timeout = new_timeout;
121 	__lpc18xx_wdt_set_timeout(lpc18xx_wdt);
122 
123 	return 0;
124 }
125 
126 static unsigned int lpc18xx_wdt_get_timeleft(struct watchdog_device *wdt_dev)
127 {
128 	struct lpc18xx_wdt_dev *lpc18xx_wdt = watchdog_get_drvdata(wdt_dev);
129 	unsigned int val;
130 
131 	val = readl(lpc18xx_wdt->base + LPC18XX_WDT_TV);
132 	return (val * LPC18XX_WDT_CLK_DIV) / lpc18xx_wdt->clk_rate;
133 }
134 
135 static int lpc18xx_wdt_start(struct watchdog_device *wdt_dev)
136 {
137 	struct lpc18xx_wdt_dev *lpc18xx_wdt = watchdog_get_drvdata(wdt_dev);
138 	unsigned int val;
139 
140 	if (timer_pending(&lpc18xx_wdt->timer))
141 		del_timer(&lpc18xx_wdt->timer);
142 
143 	val = readl(lpc18xx_wdt->base + LPC18XX_WDT_MOD);
144 	val |= LPC18XX_WDT_MOD_WDEN;
145 	val |= LPC18XX_WDT_MOD_WDRESET;
146 	writel(val, lpc18xx_wdt->base + LPC18XX_WDT_MOD);
147 
148 	/*
149 	 * Setting the WDEN bit in the WDMOD register is not sufficient to
150 	 * enable the Watchdog. A valid feed sequence must be completed after
151 	 * setting WDEN before the Watchdog is capable of generating a reset.
152 	 */
153 	lpc18xx_wdt_feed(wdt_dev);
154 
155 	return 0;
156 }
157 
158 static int lpc18xx_wdt_restart(struct watchdog_device *wdt_dev,
159 			       unsigned long action, void *data)
160 {
161 	struct lpc18xx_wdt_dev *lpc18xx_wdt = watchdog_get_drvdata(wdt_dev);
162 	unsigned long flags;
163 	int val;
164 
165 	/*
166 	 * Incorrect feed sequence causes immediate watchdog reset if enabled.
167 	 */
168 	spin_lock_irqsave(&lpc18xx_wdt->lock, flags);
169 
170 	val = readl(lpc18xx_wdt->base + LPC18XX_WDT_MOD);
171 	val |= LPC18XX_WDT_MOD_WDEN;
172 	val |= LPC18XX_WDT_MOD_WDRESET;
173 	writel(val, lpc18xx_wdt->base + LPC18XX_WDT_MOD);
174 
175 	writel(LPC18XX_WDT_FEED_MAGIC1, lpc18xx_wdt->base + LPC18XX_WDT_FEED);
176 	writel(LPC18XX_WDT_FEED_MAGIC2, lpc18xx_wdt->base + LPC18XX_WDT_FEED);
177 
178 	writel(LPC18XX_WDT_FEED_MAGIC1, lpc18xx_wdt->base + LPC18XX_WDT_FEED);
179 	writel(LPC18XX_WDT_FEED_MAGIC1, lpc18xx_wdt->base + LPC18XX_WDT_FEED);
180 
181 	spin_unlock_irqrestore(&lpc18xx_wdt->lock, flags);
182 
183 	return 0;
184 }
185 
186 static const struct watchdog_info lpc18xx_wdt_info = {
187 	.identity	= "NXP LPC18xx Watchdog",
188 	.options	= WDIOF_SETTIMEOUT |
189 			  WDIOF_KEEPALIVEPING |
190 			  WDIOF_MAGICCLOSE,
191 };
192 
193 static const struct watchdog_ops lpc18xx_wdt_ops = {
194 	.owner		= THIS_MODULE,
195 	.start		= lpc18xx_wdt_start,
196 	.stop		= lpc18xx_wdt_stop,
197 	.ping		= lpc18xx_wdt_feed,
198 	.set_timeout	= lpc18xx_wdt_set_timeout,
199 	.get_timeleft	= lpc18xx_wdt_get_timeleft,
200 	.restart        = lpc18xx_wdt_restart,
201 };
202 
203 static int lpc18xx_wdt_probe(struct platform_device *pdev)
204 {
205 	struct lpc18xx_wdt_dev *lpc18xx_wdt;
206 	struct device *dev = &pdev->dev;
207 	struct resource *res;
208 	int ret;
209 
210 	lpc18xx_wdt = devm_kzalloc(dev, sizeof(*lpc18xx_wdt), GFP_KERNEL);
211 	if (!lpc18xx_wdt)
212 		return -ENOMEM;
213 
214 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
215 	lpc18xx_wdt->base = devm_ioremap_resource(dev, res);
216 	if (IS_ERR(lpc18xx_wdt->base))
217 		return PTR_ERR(lpc18xx_wdt->base);
218 
219 	lpc18xx_wdt->reg_clk = devm_clk_get(dev, "reg");
220 	if (IS_ERR(lpc18xx_wdt->reg_clk)) {
221 		dev_err(dev, "failed to get the reg clock\n");
222 		return PTR_ERR(lpc18xx_wdt->reg_clk);
223 	}
224 
225 	lpc18xx_wdt->wdt_clk = devm_clk_get(dev, "wdtclk");
226 	if (IS_ERR(lpc18xx_wdt->wdt_clk)) {
227 		dev_err(dev, "failed to get the wdt clock\n");
228 		return PTR_ERR(lpc18xx_wdt->wdt_clk);
229 	}
230 
231 	ret = clk_prepare_enable(lpc18xx_wdt->reg_clk);
232 	if (ret) {
233 		dev_err(dev, "could not prepare or enable sys clock\n");
234 		return ret;
235 	}
236 
237 	ret = clk_prepare_enable(lpc18xx_wdt->wdt_clk);
238 	if (ret) {
239 		dev_err(dev, "could not prepare or enable wdt clock\n");
240 		goto disable_reg_clk;
241 	}
242 
243 	/* We use the clock rate to calculate timeouts */
244 	lpc18xx_wdt->clk_rate = clk_get_rate(lpc18xx_wdt->wdt_clk);
245 	if (lpc18xx_wdt->clk_rate == 0) {
246 		dev_err(dev, "failed to get clock rate\n");
247 		ret = -EINVAL;
248 		goto disable_wdt_clk;
249 	}
250 
251 	lpc18xx_wdt->wdt_dev.info = &lpc18xx_wdt_info;
252 	lpc18xx_wdt->wdt_dev.ops = &lpc18xx_wdt_ops;
253 
254 	lpc18xx_wdt->wdt_dev.min_timeout = DIV_ROUND_UP(LPC18XX_WDT_TC_MIN *
255 				LPC18XX_WDT_CLK_DIV, lpc18xx_wdt->clk_rate);
256 
257 	lpc18xx_wdt->wdt_dev.max_timeout = (LPC18XX_WDT_TC_MAX *
258 				LPC18XX_WDT_CLK_DIV) / lpc18xx_wdt->clk_rate;
259 
260 	lpc18xx_wdt->wdt_dev.timeout = min(lpc18xx_wdt->wdt_dev.max_timeout,
261 					   LPC18XX_WDT_DEF_TIMEOUT);
262 
263 	spin_lock_init(&lpc18xx_wdt->lock);
264 
265 	lpc18xx_wdt->wdt_dev.parent = dev;
266 	watchdog_set_drvdata(&lpc18xx_wdt->wdt_dev, lpc18xx_wdt);
267 
268 	ret = watchdog_init_timeout(&lpc18xx_wdt->wdt_dev, heartbeat, dev);
269 
270 	__lpc18xx_wdt_set_timeout(lpc18xx_wdt);
271 
272 	timer_setup(&lpc18xx_wdt->timer, lpc18xx_wdt_timer_feed, 0);
273 
274 	watchdog_set_nowayout(&lpc18xx_wdt->wdt_dev, nowayout);
275 	watchdog_set_restart_priority(&lpc18xx_wdt->wdt_dev, 128);
276 
277 	platform_set_drvdata(pdev, lpc18xx_wdt);
278 
279 	ret = watchdog_register_device(&lpc18xx_wdt->wdt_dev);
280 	if (ret)
281 		goto disable_wdt_clk;
282 
283 	return 0;
284 
285 disable_wdt_clk:
286 	clk_disable_unprepare(lpc18xx_wdt->wdt_clk);
287 disable_reg_clk:
288 	clk_disable_unprepare(lpc18xx_wdt->reg_clk);
289 	return ret;
290 }
291 
292 static void lpc18xx_wdt_shutdown(struct platform_device *pdev)
293 {
294 	struct lpc18xx_wdt_dev *lpc18xx_wdt = platform_get_drvdata(pdev);
295 
296 	lpc18xx_wdt_stop(&lpc18xx_wdt->wdt_dev);
297 }
298 
299 static int lpc18xx_wdt_remove(struct platform_device *pdev)
300 {
301 	struct lpc18xx_wdt_dev *lpc18xx_wdt = platform_get_drvdata(pdev);
302 
303 	dev_warn(&pdev->dev, "I quit now, hardware will probably reboot!\n");
304 	del_timer(&lpc18xx_wdt->timer);
305 
306 	watchdog_unregister_device(&lpc18xx_wdt->wdt_dev);
307 	clk_disable_unprepare(lpc18xx_wdt->wdt_clk);
308 	clk_disable_unprepare(lpc18xx_wdt->reg_clk);
309 
310 	return 0;
311 }
312 
313 static const struct of_device_id lpc18xx_wdt_match[] = {
314 	{ .compatible = "nxp,lpc1850-wwdt" },
315 	{}
316 };
317 MODULE_DEVICE_TABLE(of, lpc18xx_wdt_match);
318 
319 static struct platform_driver lpc18xx_wdt_driver = {
320 	.driver = {
321 		.name = "lpc18xx-wdt",
322 		.of_match_table	= lpc18xx_wdt_match,
323 	},
324 	.probe = lpc18xx_wdt_probe,
325 	.remove = lpc18xx_wdt_remove,
326 	.shutdown = lpc18xx_wdt_shutdown,
327 };
328 module_platform_driver(lpc18xx_wdt_driver);
329 
330 MODULE_AUTHOR("Ariel D'Alessandro <ariel@vanguardiasur.com.ar>");
331 MODULE_DESCRIPTION("NXP LPC18xx Watchdog Timer Driver");
332 MODULE_LICENSE("GPL v2");
333