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, ret;
103 	unsigned long flags;
104 	struct bcm_kona_wdt *wdt = s->private;
105 
106 	if (!wdt)
107 		return seq_puts(s, "No device pointer\n");
108 
109 	spin_lock_irqsave(&wdt->lock, flags);
110 	ctl_val = secure_register_read(wdt, SECWDOG_CTRL_REG);
111 	cur_val = secure_register_read(wdt, SECWDOG_COUNT_REG);
112 	spin_unlock_irqrestore(&wdt->lock, flags);
113 
114 	if (ctl_val < 0 || cur_val < 0) {
115 		ret = seq_puts(s, "Error accessing hardware\n");
116 	} else {
117 		int ctl, cur, ctl_sec, cur_sec, res;
118 
119 		ctl = ctl_val & SECWDOG_COUNT_MASK;
120 		res = (ctl_val & SECWDOG_RES_MASK) >> SECWDOG_CLKS_SHIFT;
121 		cur = cur_val & SECWDOG_COUNT_MASK;
122 		ctl_sec = TICKS_TO_SECS(ctl, wdt);
123 		cur_sec = TICKS_TO_SECS(cur, wdt);
124 		ret = seq_printf(s, "Resolution: %d / %d\n"
125 				"Control: %d s / %d (%#x) ticks\n"
126 				"Current: %d s / %d (%#x) ticks\n"
127 				"Busy count: %lu\n", res,
128 				wdt->resolution, ctl_sec, ctl, ctl, cur_sec,
129 				cur, cur, wdt->busy_count);
130 	}
131 
132 	return ret;
133 }
134 
135 static int bcm_kona_dbg_open(struct inode *inode, struct file *file)
136 {
137 	return single_open(file, bcm_kona_wdt_dbg_show, inode->i_private);
138 }
139 
140 static const struct file_operations bcm_kona_dbg_operations = {
141 	.open		= bcm_kona_dbg_open,
142 	.read		= seq_read,
143 	.llseek		= seq_lseek,
144 	.release	= single_release,
145 };
146 
147 static void bcm_kona_wdt_debug_init(struct platform_device *pdev)
148 {
149 	struct dentry *dir;
150 	struct bcm_kona_wdt *wdt = platform_get_drvdata(pdev);
151 
152 	if (!wdt)
153 		return;
154 
155 	wdt->debugfs = NULL;
156 
157 	dir = debugfs_create_dir(BCM_KONA_WDT_NAME, NULL);
158 	if (IS_ERR_OR_NULL(dir))
159 		return;
160 
161 	if (debugfs_create_file("info", S_IFREG | S_IRUGO, dir, wdt,
162 				&bcm_kona_dbg_operations))
163 		wdt->debugfs = dir;
164 	else
165 		debugfs_remove_recursive(dir);
166 }
167 
168 static void bcm_kona_wdt_debug_exit(struct platform_device *pdev)
169 {
170 	struct bcm_kona_wdt *wdt = platform_get_drvdata(pdev);
171 
172 	if (wdt && wdt->debugfs) {
173 		debugfs_remove_recursive(wdt->debugfs);
174 		wdt->debugfs = NULL;
175 	}
176 }
177 
178 #else
179 
180 static void bcm_kona_wdt_debug_init(struct platform_device *pdev) {}
181 static void bcm_kona_wdt_debug_exit(struct platform_device *pdev) {}
182 
183 #endif /* CONFIG_BCM_KONA_WDT_DEBUG */
184 
185 static int bcm_kona_wdt_ctrl_reg_modify(struct bcm_kona_wdt *wdt,
186 					unsigned mask, unsigned newval)
187 {
188 	int val;
189 	unsigned long flags;
190 	int ret = 0;
191 
192 	spin_lock_irqsave(&wdt->lock, flags);
193 
194 	val = secure_register_read(wdt, SECWDOG_CTRL_REG);
195 	if (val < 0) {
196 		ret = val;
197 	} else {
198 		val &= ~mask;
199 		val |= newval;
200 		writel_relaxed(val, wdt->base + SECWDOG_CTRL_REG);
201 	}
202 
203 	spin_unlock_irqrestore(&wdt->lock, flags);
204 
205 	return ret;
206 }
207 
208 static int bcm_kona_wdt_set_resolution_reg(struct bcm_kona_wdt *wdt)
209 {
210 	if (wdt->resolution > SECWDOG_MAX_RES)
211 		return -EINVAL;
212 
213 	return bcm_kona_wdt_ctrl_reg_modify(wdt, SECWDOG_RES_MASK,
214 					wdt->resolution << SECWDOG_CLKS_SHIFT);
215 }
216 
217 static int bcm_kona_wdt_set_timeout_reg(struct watchdog_device *wdog,
218 					unsigned watchdog_flags)
219 {
220 	struct bcm_kona_wdt *wdt = watchdog_get_drvdata(wdog);
221 
222 	return bcm_kona_wdt_ctrl_reg_modify(wdt, SECWDOG_COUNT_MASK,
223 					SECS_TO_TICKS(wdog->timeout, wdt) |
224 					watchdog_flags);
225 }
226 
227 static int bcm_kona_wdt_set_timeout(struct watchdog_device *wdog,
228 	unsigned int t)
229 {
230 	wdog->timeout = t;
231 	return 0;
232 }
233 
234 static unsigned int bcm_kona_wdt_get_timeleft(struct watchdog_device *wdog)
235 {
236 	struct bcm_kona_wdt *wdt = watchdog_get_drvdata(wdog);
237 	int val;
238 	unsigned long flags;
239 
240 	spin_lock_irqsave(&wdt->lock, flags);
241 	val = secure_register_read(wdt, SECWDOG_COUNT_REG);
242 	spin_unlock_irqrestore(&wdt->lock, flags);
243 
244 	if (val < 0)
245 		return val;
246 
247 	return TICKS_TO_SECS(val & SECWDOG_COUNT_MASK, wdt);
248 }
249 
250 static int bcm_kona_wdt_start(struct watchdog_device *wdog)
251 {
252 	return bcm_kona_wdt_set_timeout_reg(wdog,
253 					SECWDOG_EN_MASK | SECWDOG_SRSTEN_MASK);
254 }
255 
256 static int bcm_kona_wdt_stop(struct watchdog_device *wdog)
257 {
258 	struct bcm_kona_wdt *wdt = watchdog_get_drvdata(wdog);
259 
260 	return bcm_kona_wdt_ctrl_reg_modify(wdt, SECWDOG_EN_MASK |
261 					    SECWDOG_SRSTEN_MASK, 0);
262 }
263 
264 static struct watchdog_ops bcm_kona_wdt_ops = {
265 	.owner =	THIS_MODULE,
266 	.start =	bcm_kona_wdt_start,
267 	.stop =		bcm_kona_wdt_stop,
268 	.set_timeout =	bcm_kona_wdt_set_timeout,
269 	.get_timeleft =	bcm_kona_wdt_get_timeleft,
270 };
271 
272 static struct watchdog_info bcm_kona_wdt_info = {
273 	.options =	WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
274 			WDIOF_KEEPALIVEPING,
275 	.identity =	"Broadcom Kona Watchdog Timer",
276 };
277 
278 static struct watchdog_device bcm_kona_wdt_wdd = {
279 	.info =		&bcm_kona_wdt_info,
280 	.ops =		&bcm_kona_wdt_ops,
281 	.min_timeout =	1,
282 	.max_timeout =	SECWDOG_MAX_COUNT >> SECWDOG_DEFAULT_RESOLUTION,
283 	.timeout =	SECWDOG_MAX_COUNT >> SECWDOG_DEFAULT_RESOLUTION,
284 };
285 
286 static void bcm_kona_wdt_shutdown(struct platform_device *pdev)
287 {
288 	bcm_kona_wdt_stop(&bcm_kona_wdt_wdd);
289 }
290 
291 static int bcm_kona_wdt_probe(struct platform_device *pdev)
292 {
293 	struct device *dev = &pdev->dev;
294 	struct bcm_kona_wdt *wdt;
295 	struct resource *res;
296 	int ret;
297 
298 	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
299 	if (!wdt)
300 		return -ENOMEM;
301 
302 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
303 	wdt->base = devm_ioremap_resource(dev, res);
304 	if (IS_ERR(wdt->base))
305 		return -ENODEV;
306 
307 	wdt->resolution = SECWDOG_DEFAULT_RESOLUTION;
308 	ret = bcm_kona_wdt_set_resolution_reg(wdt);
309 	if (ret) {
310 		dev_err(dev, "Failed to set resolution (error: %d)", ret);
311 		return ret;
312 	}
313 
314 	spin_lock_init(&wdt->lock);
315 	platform_set_drvdata(pdev, wdt);
316 	watchdog_set_drvdata(&bcm_kona_wdt_wdd, wdt);
317 
318 	ret = bcm_kona_wdt_set_timeout_reg(&bcm_kona_wdt_wdd, 0);
319 	if (ret) {
320 		dev_err(dev, "Failed set watchdog timeout");
321 		return ret;
322 	}
323 
324 	ret = watchdog_register_device(&bcm_kona_wdt_wdd);
325 	if (ret) {
326 		dev_err(dev, "Failed to register watchdog device");
327 		return ret;
328 	}
329 
330 	bcm_kona_wdt_debug_init(pdev);
331 	dev_dbg(dev, "Broadcom Kona Watchdog Timer");
332 
333 	return 0;
334 }
335 
336 static int bcm_kona_wdt_remove(struct platform_device *pdev)
337 {
338 	bcm_kona_wdt_debug_exit(pdev);
339 	bcm_kona_wdt_shutdown(pdev);
340 	watchdog_unregister_device(&bcm_kona_wdt_wdd);
341 	dev_dbg(&pdev->dev, "Watchdog driver disabled");
342 
343 	return 0;
344 }
345 
346 static const struct of_device_id bcm_kona_wdt_of_match[] = {
347 	{ .compatible = "brcm,kona-wdt", },
348 	{},
349 };
350 MODULE_DEVICE_TABLE(of, bcm_kona_wdt_of_match);
351 
352 static struct platform_driver bcm_kona_wdt_driver = {
353 	.driver = {
354 			.name = BCM_KONA_WDT_NAME,
355 			.owner = THIS_MODULE,
356 			.of_match_table = bcm_kona_wdt_of_match,
357 		  },
358 	.probe = bcm_kona_wdt_probe,
359 	.remove = bcm_kona_wdt_remove,
360 	.shutdown = bcm_kona_wdt_shutdown,
361 };
362 
363 module_platform_driver(bcm_kona_wdt_driver);
364 
365 MODULE_ALIAS("platform:" BCM_KONA_WDT_NAME);
366 MODULE_AUTHOR("Markus Mayer <mmayer@broadcom.com>");
367 MODULE_DESCRIPTION("Broadcom Kona Watchdog Driver");
368 MODULE_LICENSE("GPL v2");
369