1 /*
2  * Copyright (C) 2013 Broadcom Corporation
3  *
4  * This program is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU General Public License as
6  * published by the Free Software Foundation version 2.
7  *
8  * This program is distributed "as is" WITHOUT ANY WARRANTY of any
9  * kind, whether express or implied; without even the implied warranty
10  * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
11  * GNU General Public License for more details.
12  */
13 
14 #include <linux/debugfs.h>
15 #include <linux/delay.h>
16 #include <linux/err.h>
17 #include <linux/io.h>
18 #include <linux/module.h>
19 #include <linux/of_address.h>
20 #include <linux/platform_device.h>
21 #include <linux/watchdog.h>
22 
23 #define SECWDOG_CTRL_REG		0x00000000
24 #define SECWDOG_COUNT_REG		0x00000004
25 
26 #define SECWDOG_RESERVED_MASK		0x1dffffff
27 #define SECWDOG_WD_LOAD_FLAG		0x10000000
28 #define SECWDOG_EN_MASK			0x08000000
29 #define SECWDOG_SRSTEN_MASK		0x04000000
30 #define SECWDOG_RES_MASK		0x00f00000
31 #define SECWDOG_COUNT_MASK		0x000fffff
32 
33 #define SECWDOG_MAX_COUNT		SECWDOG_COUNT_MASK
34 #define SECWDOG_CLKS_SHIFT		20
35 #define SECWDOG_MAX_RES			15
36 #define SECWDOG_DEFAULT_RESOLUTION	4
37 #define SECWDOG_MAX_TRY			1000
38 
39 #define SECS_TO_TICKS(x, w)		((x) << (w)->resolution)
40 #define TICKS_TO_SECS(x, w)		((x) >> (w)->resolution)
41 
42 #define BCM_KONA_WDT_NAME		"bcm_kona_wdt"
43 
44 struct bcm_kona_wdt {
45 	void __iomem *base;
46 	/*
47 	 * One watchdog tick is 1/(2^resolution) seconds. Resolution can take
48 	 * the values 0-15, meaning one tick can be 1s to 30.52us. Our default
49 	 * resolution of 4 means one tick is 62.5ms.
50 	 *
51 	 * The watchdog counter is 20 bits. Depending on resolution, the maximum
52 	 * counter value of 0xfffff expires after about 12 days (resolution 0)
53 	 * down to only 32s (resolution 15). The default resolution of 4 gives
54 	 * us a maximum of about 18 hours and 12 minutes before the watchdog
55 	 * times out.
56 	 */
57 	int resolution;
58 	spinlock_t lock;
59 #ifdef CONFIG_BCM_KONA_WDT_DEBUG
60 	unsigned long busy_count;
61 	struct dentry *debugfs;
62 #endif
63 };
64 
65 static int secure_register_read(struct bcm_kona_wdt *wdt, uint32_t offset)
66 {
67 	uint32_t val;
68 	unsigned count = 0;
69 
70 	/*
71 	 * If the WD_LOAD_FLAG is set, the watchdog counter field is being
72 	 * updated in hardware. Once the WD timer is updated in hardware, it
73 	 * gets cleared.
74 	 */
75 	do {
76 		if (unlikely(count > 1))
77 			udelay(5);
78 		val = readl_relaxed(wdt->base + offset);
79 		count++;
80 	} while ((val & SECWDOG_WD_LOAD_FLAG) && count < SECWDOG_MAX_TRY);
81 
82 #ifdef CONFIG_BCM_KONA_WDT_DEBUG
83 	/* Remember the maximum number iterations due to WD_LOAD_FLAG */
84 	if (count > wdt->busy_count)
85 		wdt->busy_count = count;
86 #endif
87 
88 	/* This is the only place we return a negative value. */
89 	if (val & SECWDOG_WD_LOAD_FLAG)
90 		return -ETIMEDOUT;
91 
92 	/* We always mask out reserved bits. */
93 	val &= SECWDOG_RESERVED_MASK;
94 
95 	return val;
96 }
97 
98 #ifdef CONFIG_BCM_KONA_WDT_DEBUG
99 
100 static int bcm_kona_wdt_dbg_show(struct seq_file *s, void *data)
101 {
102 	int ctl_val, cur_val;
103 	unsigned long flags;
104 	struct bcm_kona_wdt *wdt = s->private;
105 
106 	if (!wdt) {
107 		seq_puts(s, "No device pointer\n");
108 		return 0;
109 	}
110 
111 	spin_lock_irqsave(&wdt->lock, flags);
112 	ctl_val = secure_register_read(wdt, SECWDOG_CTRL_REG);
113 	cur_val = secure_register_read(wdt, SECWDOG_COUNT_REG);
114 	spin_unlock_irqrestore(&wdt->lock, flags);
115 
116 	if (ctl_val < 0 || cur_val < 0) {
117 		seq_puts(s, "Error accessing hardware\n");
118 	} else {
119 		int ctl, cur, ctl_sec, cur_sec, res;
120 
121 		ctl = ctl_val & SECWDOG_COUNT_MASK;
122 		res = (ctl_val & SECWDOG_RES_MASK) >> SECWDOG_CLKS_SHIFT;
123 		cur = cur_val & SECWDOG_COUNT_MASK;
124 		ctl_sec = TICKS_TO_SECS(ctl, wdt);
125 		cur_sec = TICKS_TO_SECS(cur, wdt);
126 		seq_printf(s,
127 			   "Resolution: %d / %d\n"
128 			   "Control: %d s / %d (%#x) ticks\n"
129 			   "Current: %d s / %d (%#x) ticks\n"
130 			   "Busy count: %lu\n",
131 			   res, wdt->resolution,
132 			   ctl_sec, ctl, ctl,
133 			   cur_sec, cur, cur,
134 			   wdt->busy_count);
135 	}
136 
137 	return 0;
138 }
139 
140 static int bcm_kona_dbg_open(struct inode *inode, struct file *file)
141 {
142 	return single_open(file, bcm_kona_wdt_dbg_show, inode->i_private);
143 }
144 
145 static const struct file_operations bcm_kona_dbg_operations = {
146 	.open		= bcm_kona_dbg_open,
147 	.read		= seq_read,
148 	.llseek		= seq_lseek,
149 	.release	= single_release,
150 };
151 
152 static void bcm_kona_wdt_debug_init(struct platform_device *pdev)
153 {
154 	struct dentry *dir;
155 	struct bcm_kona_wdt *wdt = platform_get_drvdata(pdev);
156 
157 	if (!wdt)
158 		return;
159 
160 	wdt->debugfs = NULL;
161 
162 	dir = debugfs_create_dir(BCM_KONA_WDT_NAME, NULL);
163 	if (IS_ERR_OR_NULL(dir))
164 		return;
165 
166 	if (debugfs_create_file("info", S_IFREG | S_IRUGO, dir, wdt,
167 				&bcm_kona_dbg_operations))
168 		wdt->debugfs = dir;
169 	else
170 		debugfs_remove_recursive(dir);
171 }
172 
173 static void bcm_kona_wdt_debug_exit(struct platform_device *pdev)
174 {
175 	struct bcm_kona_wdt *wdt = platform_get_drvdata(pdev);
176 
177 	if (wdt && wdt->debugfs) {
178 		debugfs_remove_recursive(wdt->debugfs);
179 		wdt->debugfs = NULL;
180 	}
181 }
182 
183 #else
184 
185 static void bcm_kona_wdt_debug_init(struct platform_device *pdev) {}
186 static void bcm_kona_wdt_debug_exit(struct platform_device *pdev) {}
187 
188 #endif /* CONFIG_BCM_KONA_WDT_DEBUG */
189 
190 static int bcm_kona_wdt_ctrl_reg_modify(struct bcm_kona_wdt *wdt,
191 					unsigned mask, unsigned newval)
192 {
193 	int val;
194 	unsigned long flags;
195 	int ret = 0;
196 
197 	spin_lock_irqsave(&wdt->lock, flags);
198 
199 	val = secure_register_read(wdt, SECWDOG_CTRL_REG);
200 	if (val < 0) {
201 		ret = val;
202 	} else {
203 		val &= ~mask;
204 		val |= newval;
205 		writel_relaxed(val, wdt->base + SECWDOG_CTRL_REG);
206 	}
207 
208 	spin_unlock_irqrestore(&wdt->lock, flags);
209 
210 	return ret;
211 }
212 
213 static int bcm_kona_wdt_set_resolution_reg(struct bcm_kona_wdt *wdt)
214 {
215 	if (wdt->resolution > SECWDOG_MAX_RES)
216 		return -EINVAL;
217 
218 	return bcm_kona_wdt_ctrl_reg_modify(wdt, SECWDOG_RES_MASK,
219 					wdt->resolution << SECWDOG_CLKS_SHIFT);
220 }
221 
222 static int bcm_kona_wdt_set_timeout_reg(struct watchdog_device *wdog,
223 					unsigned watchdog_flags)
224 {
225 	struct bcm_kona_wdt *wdt = watchdog_get_drvdata(wdog);
226 
227 	return bcm_kona_wdt_ctrl_reg_modify(wdt, SECWDOG_COUNT_MASK,
228 					SECS_TO_TICKS(wdog->timeout, wdt) |
229 					watchdog_flags);
230 }
231 
232 static int bcm_kona_wdt_set_timeout(struct watchdog_device *wdog,
233 	unsigned int t)
234 {
235 	wdog->timeout = t;
236 	return 0;
237 }
238 
239 static unsigned int bcm_kona_wdt_get_timeleft(struct watchdog_device *wdog)
240 {
241 	struct bcm_kona_wdt *wdt = watchdog_get_drvdata(wdog);
242 	int val;
243 	unsigned long flags;
244 
245 	spin_lock_irqsave(&wdt->lock, flags);
246 	val = secure_register_read(wdt, SECWDOG_COUNT_REG);
247 	spin_unlock_irqrestore(&wdt->lock, flags);
248 
249 	if (val < 0)
250 		return val;
251 
252 	return TICKS_TO_SECS(val & SECWDOG_COUNT_MASK, wdt);
253 }
254 
255 static int bcm_kona_wdt_start(struct watchdog_device *wdog)
256 {
257 	return bcm_kona_wdt_set_timeout_reg(wdog,
258 					SECWDOG_EN_MASK | SECWDOG_SRSTEN_MASK);
259 }
260 
261 static int bcm_kona_wdt_stop(struct watchdog_device *wdog)
262 {
263 	struct bcm_kona_wdt *wdt = watchdog_get_drvdata(wdog);
264 
265 	return bcm_kona_wdt_ctrl_reg_modify(wdt, SECWDOG_EN_MASK |
266 					    SECWDOG_SRSTEN_MASK, 0);
267 }
268 
269 static struct watchdog_ops bcm_kona_wdt_ops = {
270 	.owner =	THIS_MODULE,
271 	.start =	bcm_kona_wdt_start,
272 	.stop =		bcm_kona_wdt_stop,
273 	.set_timeout =	bcm_kona_wdt_set_timeout,
274 	.get_timeleft =	bcm_kona_wdt_get_timeleft,
275 };
276 
277 static struct watchdog_info bcm_kona_wdt_info = {
278 	.options =	WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
279 			WDIOF_KEEPALIVEPING,
280 	.identity =	"Broadcom Kona Watchdog Timer",
281 };
282 
283 static struct watchdog_device bcm_kona_wdt_wdd = {
284 	.info =		&bcm_kona_wdt_info,
285 	.ops =		&bcm_kona_wdt_ops,
286 	.min_timeout =	1,
287 	.max_timeout =	SECWDOG_MAX_COUNT >> SECWDOG_DEFAULT_RESOLUTION,
288 	.timeout =	SECWDOG_MAX_COUNT >> SECWDOG_DEFAULT_RESOLUTION,
289 };
290 
291 static void bcm_kona_wdt_shutdown(struct platform_device *pdev)
292 {
293 	bcm_kona_wdt_stop(&bcm_kona_wdt_wdd);
294 }
295 
296 static int bcm_kona_wdt_probe(struct platform_device *pdev)
297 {
298 	struct device *dev = &pdev->dev;
299 	struct bcm_kona_wdt *wdt;
300 	struct resource *res;
301 	int ret;
302 
303 	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
304 	if (!wdt)
305 		return -ENOMEM;
306 
307 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
308 	wdt->base = devm_ioremap_resource(dev, res);
309 	if (IS_ERR(wdt->base))
310 		return -ENODEV;
311 
312 	wdt->resolution = SECWDOG_DEFAULT_RESOLUTION;
313 	ret = bcm_kona_wdt_set_resolution_reg(wdt);
314 	if (ret) {
315 		dev_err(dev, "Failed to set resolution (error: %d)", ret);
316 		return ret;
317 	}
318 
319 	spin_lock_init(&wdt->lock);
320 	platform_set_drvdata(pdev, wdt);
321 	watchdog_set_drvdata(&bcm_kona_wdt_wdd, wdt);
322 
323 	ret = bcm_kona_wdt_set_timeout_reg(&bcm_kona_wdt_wdd, 0);
324 	if (ret) {
325 		dev_err(dev, "Failed set watchdog timeout");
326 		return ret;
327 	}
328 
329 	ret = watchdog_register_device(&bcm_kona_wdt_wdd);
330 	if (ret) {
331 		dev_err(dev, "Failed to register watchdog device");
332 		return ret;
333 	}
334 
335 	bcm_kona_wdt_debug_init(pdev);
336 	dev_dbg(dev, "Broadcom Kona Watchdog Timer");
337 
338 	return 0;
339 }
340 
341 static int bcm_kona_wdt_remove(struct platform_device *pdev)
342 {
343 	bcm_kona_wdt_debug_exit(pdev);
344 	bcm_kona_wdt_shutdown(pdev);
345 	watchdog_unregister_device(&bcm_kona_wdt_wdd);
346 	dev_dbg(&pdev->dev, "Watchdog driver disabled");
347 
348 	return 0;
349 }
350 
351 static const struct of_device_id bcm_kona_wdt_of_match[] = {
352 	{ .compatible = "brcm,kona-wdt", },
353 	{},
354 };
355 MODULE_DEVICE_TABLE(of, bcm_kona_wdt_of_match);
356 
357 static struct platform_driver bcm_kona_wdt_driver = {
358 	.driver = {
359 			.name = BCM_KONA_WDT_NAME,
360 			.of_match_table = bcm_kona_wdt_of_match,
361 		  },
362 	.probe = bcm_kona_wdt_probe,
363 	.remove = bcm_kona_wdt_remove,
364 	.shutdown = bcm_kona_wdt_shutdown,
365 };
366 
367 module_platform_driver(bcm_kona_wdt_driver);
368 
369 MODULE_ALIAS("platform:" BCM_KONA_WDT_NAME);
370 MODULE_AUTHOR("Markus Mayer <mmayer@broadcom.com>");
371 MODULE_DESCRIPTION("Broadcom Kona Watchdog Driver");
372 MODULE_LICENSE("GPL v2");
373