1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * NXP LPC18xx Watchdog Timer (WDT)
4  *
5  * Copyright (c) 2015 Ariel D'Alessandro <ariel@vanguardiasur.com>
6  *
7  * Notes
8  * -----
9  * The Watchdog consists of a fixed divide-by-4 clock pre-scaler and a 24-bit
10  * counter which decrements on every clock cycle.
11  */
12 
13 #include <linux/clk.h>
14 #include <linux/io.h>
15 #include <linux/module.h>
16 #include <linux/of.h>
17 #include <linux/platform_device.h>
18 #include <linux/watchdog.h>
19 
20 /* Registers */
21 #define LPC18XX_WDT_MOD			0x00
22 #define LPC18XX_WDT_MOD_WDEN		BIT(0)
23 #define LPC18XX_WDT_MOD_WDRESET		BIT(1)
24 
25 #define LPC18XX_WDT_TC			0x04
26 #define LPC18XX_WDT_TC_MIN		0xff
27 #define LPC18XX_WDT_TC_MAX		0xffffff
28 
29 #define LPC18XX_WDT_FEED		0x08
30 #define LPC18XX_WDT_FEED_MAGIC1		0xaa
31 #define LPC18XX_WDT_FEED_MAGIC2		0x55
32 
33 #define LPC18XX_WDT_TV			0x0c
34 
35 /* Clock pre-scaler */
36 #define LPC18XX_WDT_CLK_DIV		4
37 
38 /* Timeout values in seconds */
39 #define LPC18XX_WDT_DEF_TIMEOUT		30U
40 
41 static int heartbeat;
42 module_param(heartbeat, int, 0);
43 MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds (default="
44 		 __MODULE_STRING(LPC18XX_WDT_DEF_TIMEOUT) ")");
45 
46 static bool nowayout = WATCHDOG_NOWAYOUT;
47 module_param(nowayout, bool, 0);
48 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
49 		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
50 
51 struct lpc18xx_wdt_dev {
52 	struct watchdog_device	wdt_dev;
53 	struct clk		*reg_clk;
54 	struct clk		*wdt_clk;
55 	unsigned long		clk_rate;
56 	void __iomem		*base;
57 	struct timer_list	timer;
58 	spinlock_t		lock;
59 };
60 
61 static int lpc18xx_wdt_feed(struct watchdog_device *wdt_dev)
62 {
63 	struct lpc18xx_wdt_dev *lpc18xx_wdt = watchdog_get_drvdata(wdt_dev);
64 	unsigned long flags;
65 
66 	/*
67 	 * An abort condition will occur if an interrupt happens during the feed
68 	 * sequence.
69 	 */
70 	spin_lock_irqsave(&lpc18xx_wdt->lock, flags);
71 	writel(LPC18XX_WDT_FEED_MAGIC1, lpc18xx_wdt->base + LPC18XX_WDT_FEED);
72 	writel(LPC18XX_WDT_FEED_MAGIC2, lpc18xx_wdt->base + LPC18XX_WDT_FEED);
73 	spin_unlock_irqrestore(&lpc18xx_wdt->lock, flags);
74 
75 	return 0;
76 }
77 
78 static void lpc18xx_wdt_timer_feed(struct timer_list *t)
79 {
80 	struct lpc18xx_wdt_dev *lpc18xx_wdt = from_timer(lpc18xx_wdt, t, timer);
81 	struct watchdog_device *wdt_dev = &lpc18xx_wdt->wdt_dev;
82 
83 	lpc18xx_wdt_feed(wdt_dev);
84 
85 	/* Use safe value (1/2 of real timeout) */
86 	mod_timer(&lpc18xx_wdt->timer, jiffies +
87 		  msecs_to_jiffies((wdt_dev->timeout * MSEC_PER_SEC) / 2));
88 }
89 
90 /*
91  * Since LPC18xx Watchdog cannot be disabled in hardware, we must keep feeding
92  * it with a timer until userspace watchdog software takes over.
93  */
94 static int lpc18xx_wdt_stop(struct watchdog_device *wdt_dev)
95 {
96 	struct lpc18xx_wdt_dev *lpc18xx_wdt = watchdog_get_drvdata(wdt_dev);
97 
98 	lpc18xx_wdt_timer_feed(&lpc18xx_wdt->timer);
99 
100 	return 0;
101 }
102 
103 static void __lpc18xx_wdt_set_timeout(struct lpc18xx_wdt_dev *lpc18xx_wdt)
104 {
105 	unsigned int val;
106 
107 	val = DIV_ROUND_UP(lpc18xx_wdt->wdt_dev.timeout * lpc18xx_wdt->clk_rate,
108 			   LPC18XX_WDT_CLK_DIV);
109 	writel(val, lpc18xx_wdt->base + LPC18XX_WDT_TC);
110 }
111 
112 static int lpc18xx_wdt_set_timeout(struct watchdog_device *wdt_dev,
113 				   unsigned int new_timeout)
114 {
115 	struct lpc18xx_wdt_dev *lpc18xx_wdt = watchdog_get_drvdata(wdt_dev);
116 
117 	lpc18xx_wdt->wdt_dev.timeout = new_timeout;
118 	__lpc18xx_wdt_set_timeout(lpc18xx_wdt);
119 
120 	return 0;
121 }
122 
123 static unsigned int lpc18xx_wdt_get_timeleft(struct watchdog_device *wdt_dev)
124 {
125 	struct lpc18xx_wdt_dev *lpc18xx_wdt = watchdog_get_drvdata(wdt_dev);
126 	unsigned int val;
127 
128 	val = readl(lpc18xx_wdt->base + LPC18XX_WDT_TV);
129 	return (val * LPC18XX_WDT_CLK_DIV) / lpc18xx_wdt->clk_rate;
130 }
131 
132 static int lpc18xx_wdt_start(struct watchdog_device *wdt_dev)
133 {
134 	struct lpc18xx_wdt_dev *lpc18xx_wdt = watchdog_get_drvdata(wdt_dev);
135 	unsigned int val;
136 
137 	if (timer_pending(&lpc18xx_wdt->timer))
138 		del_timer(&lpc18xx_wdt->timer);
139 
140 	val = readl(lpc18xx_wdt->base + LPC18XX_WDT_MOD);
141 	val |= LPC18XX_WDT_MOD_WDEN;
142 	val |= LPC18XX_WDT_MOD_WDRESET;
143 	writel(val, lpc18xx_wdt->base + LPC18XX_WDT_MOD);
144 
145 	/*
146 	 * Setting the WDEN bit in the WDMOD register is not sufficient to
147 	 * enable the Watchdog. A valid feed sequence must be completed after
148 	 * setting WDEN before the Watchdog is capable of generating a reset.
149 	 */
150 	lpc18xx_wdt_feed(wdt_dev);
151 
152 	return 0;
153 }
154 
155 static int lpc18xx_wdt_restart(struct watchdog_device *wdt_dev,
156 			       unsigned long action, void *data)
157 {
158 	struct lpc18xx_wdt_dev *lpc18xx_wdt = watchdog_get_drvdata(wdt_dev);
159 	unsigned long flags;
160 	int val;
161 
162 	/*
163 	 * Incorrect feed sequence causes immediate watchdog reset if enabled.
164 	 */
165 	spin_lock_irqsave(&lpc18xx_wdt->lock, flags);
166 
167 	val = readl(lpc18xx_wdt->base + LPC18XX_WDT_MOD);
168 	val |= LPC18XX_WDT_MOD_WDEN;
169 	val |= LPC18XX_WDT_MOD_WDRESET;
170 	writel(val, lpc18xx_wdt->base + LPC18XX_WDT_MOD);
171 
172 	writel(LPC18XX_WDT_FEED_MAGIC1, lpc18xx_wdt->base + LPC18XX_WDT_FEED);
173 	writel(LPC18XX_WDT_FEED_MAGIC2, lpc18xx_wdt->base + LPC18XX_WDT_FEED);
174 
175 	writel(LPC18XX_WDT_FEED_MAGIC1, lpc18xx_wdt->base + LPC18XX_WDT_FEED);
176 	writel(LPC18XX_WDT_FEED_MAGIC1, lpc18xx_wdt->base + LPC18XX_WDT_FEED);
177 
178 	spin_unlock_irqrestore(&lpc18xx_wdt->lock, flags);
179 
180 	return 0;
181 }
182 
183 static const struct watchdog_info lpc18xx_wdt_info = {
184 	.identity	= "NXP LPC18xx Watchdog",
185 	.options	= WDIOF_SETTIMEOUT |
186 			  WDIOF_KEEPALIVEPING |
187 			  WDIOF_MAGICCLOSE,
188 };
189 
190 static const struct watchdog_ops lpc18xx_wdt_ops = {
191 	.owner		= THIS_MODULE,
192 	.start		= lpc18xx_wdt_start,
193 	.stop		= lpc18xx_wdt_stop,
194 	.ping		= lpc18xx_wdt_feed,
195 	.set_timeout	= lpc18xx_wdt_set_timeout,
196 	.get_timeleft	= lpc18xx_wdt_get_timeleft,
197 	.restart        = lpc18xx_wdt_restart,
198 };
199 
200 static void lpc18xx_clk_disable_unprepare(void *data)
201 {
202 	clk_disable_unprepare(data);
203 }
204 
205 static int lpc18xx_wdt_probe(struct platform_device *pdev)
206 {
207 	struct lpc18xx_wdt_dev *lpc18xx_wdt;
208 	struct device *dev = &pdev->dev;
209 	int ret;
210 
211 	lpc18xx_wdt = devm_kzalloc(dev, sizeof(*lpc18xx_wdt), GFP_KERNEL);
212 	if (!lpc18xx_wdt)
213 		return -ENOMEM;
214 
215 	lpc18xx_wdt->base = devm_platform_ioremap_resource(pdev, 0);
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 	ret = devm_add_action_or_reset(dev, lpc18xx_clk_disable_unprepare,
237 				       lpc18xx_wdt->reg_clk);
238 	if (ret)
239 		return ret;
240 
241 	ret = clk_prepare_enable(lpc18xx_wdt->wdt_clk);
242 	if (ret) {
243 		dev_err(dev, "could not prepare or enable wdt clock\n");
244 		return ret;
245 	}
246 	ret = devm_add_action_or_reset(dev, lpc18xx_clk_disable_unprepare,
247 				       lpc18xx_wdt->wdt_clk);
248 	if (ret)
249 		return ret;
250 
251 	/* We use the clock rate to calculate timeouts */
252 	lpc18xx_wdt->clk_rate = clk_get_rate(lpc18xx_wdt->wdt_clk);
253 	if (lpc18xx_wdt->clk_rate == 0) {
254 		dev_err(dev, "failed to get clock rate\n");
255 		return -EINVAL;
256 	}
257 
258 	lpc18xx_wdt->wdt_dev.info = &lpc18xx_wdt_info;
259 	lpc18xx_wdt->wdt_dev.ops = &lpc18xx_wdt_ops;
260 
261 	lpc18xx_wdt->wdt_dev.min_timeout = DIV_ROUND_UP(LPC18XX_WDT_TC_MIN *
262 				LPC18XX_WDT_CLK_DIV, lpc18xx_wdt->clk_rate);
263 
264 	lpc18xx_wdt->wdt_dev.max_timeout = (LPC18XX_WDT_TC_MAX *
265 				LPC18XX_WDT_CLK_DIV) / lpc18xx_wdt->clk_rate;
266 
267 	lpc18xx_wdt->wdt_dev.timeout = min(lpc18xx_wdt->wdt_dev.max_timeout,
268 					   LPC18XX_WDT_DEF_TIMEOUT);
269 
270 	spin_lock_init(&lpc18xx_wdt->lock);
271 
272 	lpc18xx_wdt->wdt_dev.parent = dev;
273 	watchdog_set_drvdata(&lpc18xx_wdt->wdt_dev, lpc18xx_wdt);
274 
275 	watchdog_init_timeout(&lpc18xx_wdt->wdt_dev, heartbeat, dev);
276 
277 	__lpc18xx_wdt_set_timeout(lpc18xx_wdt);
278 
279 	timer_setup(&lpc18xx_wdt->timer, lpc18xx_wdt_timer_feed, 0);
280 
281 	watchdog_set_nowayout(&lpc18xx_wdt->wdt_dev, nowayout);
282 	watchdog_set_restart_priority(&lpc18xx_wdt->wdt_dev, 128);
283 
284 	platform_set_drvdata(pdev, lpc18xx_wdt);
285 
286 	watchdog_stop_on_reboot(&lpc18xx_wdt->wdt_dev);
287 	return devm_watchdog_register_device(dev, &lpc18xx_wdt->wdt_dev);
288 }
289 
290 static int lpc18xx_wdt_remove(struct platform_device *pdev)
291 {
292 	struct lpc18xx_wdt_dev *lpc18xx_wdt = platform_get_drvdata(pdev);
293 
294 	dev_warn(&pdev->dev, "I quit now, hardware will probably reboot!\n");
295 	del_timer_sync(&lpc18xx_wdt->timer);
296 
297 	return 0;
298 }
299 
300 static const struct of_device_id lpc18xx_wdt_match[] = {
301 	{ .compatible = "nxp,lpc1850-wwdt" },
302 	{}
303 };
304 MODULE_DEVICE_TABLE(of, lpc18xx_wdt_match);
305 
306 static struct platform_driver lpc18xx_wdt_driver = {
307 	.driver = {
308 		.name = "lpc18xx-wdt",
309 		.of_match_table	= lpc18xx_wdt_match,
310 	},
311 	.probe = lpc18xx_wdt_probe,
312 	.remove = lpc18xx_wdt_remove,
313 };
314 module_platform_driver(lpc18xx_wdt_driver);
315 
316 MODULE_AUTHOR("Ariel D'Alessandro <ariel@vanguardiasur.com.ar>");
317 MODULE_DESCRIPTION("NXP LPC18xx Watchdog Timer Driver");
318 MODULE_LICENSE("GPL v2");
319