1/*
2 * Watchdog driver for Atmel AT32AP700X devices
3 *
4 * Copyright (C) 2005-2006 Atmel Corporation
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 *
10 *
11 * Errata: WDT Clear is blocked after WDT Reset
12 *
13 * A watchdog timer event will, after reset, block writes to the WDT_CLEAR
14 * register, preventing the program to clear the next Watchdog Timer Reset.
15 *
16 * If you still want to use the WDT after a WDT reset a small code can be
17 * insterted at the startup checking the AVR32_PM.rcause register for WDT reset
18 * and use a GPIO pin to reset the system. This method requires that one of the
19 * GPIO pins are available and connected externally to the RESET_N pin. After
20 * the GPIO pin has pulled down the reset line the GPIO will be reset and leave
21 * the pin tristated with pullup.
22 */
23
24#include <linux/init.h>
25#include <linux/kernel.h>
26#include <linux/module.h>
27#include <linux/moduleparam.h>
28#include <linux/miscdevice.h>
29#include <linux/fs.h>
30#include <linux/platform_device.h>
31#include <linux/watchdog.h>
32#include <linux/uaccess.h>
33#include <linux/io.h>
34#include <linux/spinlock.h>
35#include <linux/slab.h>
36
37#define TIMEOUT_MIN		1
38#define TIMEOUT_MAX		2
39#define TIMEOUT_DEFAULT		TIMEOUT_MAX
40
41/* module parameters */
42static int timeout =  TIMEOUT_DEFAULT;
43module_param(timeout, int, 0);
44MODULE_PARM_DESC(timeout,
45		"Timeout value. Limited to be 1 or 2 seconds. (default="
46		__MODULE_STRING(TIMEOUT_DEFAULT) ")");
47
48static bool nowayout = WATCHDOG_NOWAYOUT;
49module_param(nowayout, bool, 0);
50MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
51		__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
52
53/* Watchdog registers and write/read macro */
54#define WDT_CTRL		0x00
55#define WDT_CTRL_EN		   0
56#define WDT_CTRL_PSEL		   8
57#define WDT_CTRL_KEY		  24
58
59#define WDT_CLR			0x04
60
61#define WDT_RCAUSE		0x10
62#define WDT_RCAUSE_POR		   0
63#define WDT_RCAUSE_EXT		   2
64#define WDT_RCAUSE_WDT		   3
65#define WDT_RCAUSE_JTAG		   4
66#define WDT_RCAUSE_SERP		   5
67
68#define WDT_BIT(name)		(1 << WDT_##name)
69#define WDT_BF(name, value)	((value) << WDT_##name)
70
71#define wdt_readl(dev, reg)				\
72	__raw_readl((dev)->regs + WDT_##reg)
73#define wdt_writel(dev, reg, value)			\
74	__raw_writel((value), (dev)->regs + WDT_##reg)
75
76struct wdt_at32ap700x {
77	void __iomem		*regs;
78	spinlock_t		io_lock;
79	int			timeout;
80	int			boot_status;
81	unsigned long		users;
82	struct miscdevice	miscdev;
83};
84
85static struct wdt_at32ap700x *wdt;
86static char expect_release;
87
88/*
89 * Disable the watchdog.
90 */
91static inline void at32_wdt_stop(void)
92{
93	unsigned long psel;
94
95	spin_lock(&wdt->io_lock);
96	psel = wdt_readl(wdt, CTRL) & WDT_BF(CTRL_PSEL, 0x0f);
97	wdt_writel(wdt, CTRL, psel | WDT_BF(CTRL_KEY, 0x55));
98	wdt_writel(wdt, CTRL, psel | WDT_BF(CTRL_KEY, 0xaa));
99	spin_unlock(&wdt->io_lock);
100}
101
102/*
103 * Enable and reset the watchdog.
104 */
105static inline void at32_wdt_start(void)
106{
107	/* 0xf is 2^16 divider = 2 sec, 0xe is 2^15 divider = 1 sec */
108	unsigned long psel = (wdt->timeout > 1) ? 0xf : 0xe;
109
110	spin_lock(&wdt->io_lock);
111	wdt_writel(wdt, CTRL, WDT_BIT(CTRL_EN)
112			| WDT_BF(CTRL_PSEL, psel)
113			| WDT_BF(CTRL_KEY, 0x55));
114	wdt_writel(wdt, CTRL, WDT_BIT(CTRL_EN)
115			| WDT_BF(CTRL_PSEL, psel)
116			| WDT_BF(CTRL_KEY, 0xaa));
117	spin_unlock(&wdt->io_lock);
118}
119
120/*
121 * Pat the watchdog timer.
122 */
123static inline void at32_wdt_pat(void)
124{
125	spin_lock(&wdt->io_lock);
126	wdt_writel(wdt, CLR, 0x42);
127	spin_unlock(&wdt->io_lock);
128}
129
130/*
131 * Watchdog device is opened, and watchdog starts running.
132 */
133static int at32_wdt_open(struct inode *inode, struct file *file)
134{
135	if (test_and_set_bit(1, &wdt->users))
136		return -EBUSY;
137
138	at32_wdt_start();
139	return nonseekable_open(inode, file);
140}
141
142/*
143 * Close the watchdog device.
144 */
145static int at32_wdt_close(struct inode *inode, struct file *file)
146{
147	if (expect_release == 42) {
148		at32_wdt_stop();
149	} else {
150		dev_dbg(wdt->miscdev.parent,
151			"unexpected close, not stopping watchdog!\n");
152		at32_wdt_pat();
153	}
154	clear_bit(1, &wdt->users);
155	expect_release = 0;
156	return 0;
157}
158
159/*
160 * Change the watchdog time interval.
161 */
162static int at32_wdt_settimeout(int time)
163{
164	/*
165	 * All counting occurs at 1 / SLOW_CLOCK (32 kHz) and max prescaler is
166	 * 2 ^ 16 allowing up to 2 seconds timeout.
167	 */
168	if ((time < TIMEOUT_MIN) || (time > TIMEOUT_MAX))
169		return -EINVAL;
170
171	/*
172	 * Set new watchdog time. It will be used when at32_wdt_start() is
173	 * called.
174	 */
175	wdt->timeout = time;
176	return 0;
177}
178
179/*
180 * Get the watchdog status.
181 */
182static int at32_wdt_get_status(void)
183{
184	int rcause;
185	int status = 0;
186
187	rcause = wdt_readl(wdt, RCAUSE);
188
189	switch (rcause) {
190	case WDT_BIT(RCAUSE_EXT):
191		status = WDIOF_EXTERN1;
192		break;
193	case WDT_BIT(RCAUSE_WDT):
194		status = WDIOF_CARDRESET;
195		break;
196	case WDT_BIT(RCAUSE_POR):  /* fall through */
197	case WDT_BIT(RCAUSE_JTAG): /* fall through */
198	case WDT_BIT(RCAUSE_SERP): /* fall through */
199	default:
200		break;
201	}
202
203	return status;
204}
205
206static const struct watchdog_info at32_wdt_info = {
207	.identity	= "at32ap700x watchdog",
208	.options	= WDIOF_SETTIMEOUT |
209			  WDIOF_KEEPALIVEPING |
210			  WDIOF_MAGICCLOSE,
211};
212
213/*
214 * Handle commands from user-space.
215 */
216static long at32_wdt_ioctl(struct file *file,
217				unsigned int cmd, unsigned long arg)
218{
219	int ret = -ENOTTY;
220	int time;
221	void __user *argp = (void __user *)arg;
222	int __user *p = argp;
223
224	switch (cmd) {
225	case WDIOC_GETSUPPORT:
226		ret = copy_to_user(argp, &at32_wdt_info,
227				sizeof(at32_wdt_info)) ? -EFAULT : 0;
228		break;
229	case WDIOC_GETSTATUS:
230		ret = put_user(0, p);
231		break;
232	case WDIOC_GETBOOTSTATUS:
233		ret = put_user(wdt->boot_status, p);
234		break;
235	case WDIOC_SETOPTIONS:
236		ret = get_user(time, p);
237		if (ret)
238			break;
239		if (time & WDIOS_DISABLECARD)
240			at32_wdt_stop();
241		if (time & WDIOS_ENABLECARD)
242			at32_wdt_start();
243		ret = 0;
244		break;
245	case WDIOC_KEEPALIVE:
246		at32_wdt_pat();
247		ret = 0;
248		break;
249	case WDIOC_SETTIMEOUT:
250		ret = get_user(time, p);
251		if (ret)
252			break;
253		ret = at32_wdt_settimeout(time);
254		if (ret)
255			break;
256		/* Enable new time value */
257		at32_wdt_start();
258		/* fall through */
259	case WDIOC_GETTIMEOUT:
260		ret = put_user(wdt->timeout, p);
261		break;
262	}
263
264	return ret;
265}
266
267static ssize_t at32_wdt_write(struct file *file, const char __user *data,
268				size_t len, loff_t *ppos)
269{
270	/* See if we got the magic character 'V' and reload the timer */
271	if (len) {
272		if (!nowayout) {
273			size_t i;
274
275			/*
276			 * note: just in case someone wrote the magic
277			 * character five months ago...
278			 */
279			expect_release = 0;
280
281			/*
282			 * scan to see whether or not we got the magic
283			 * character
284			 */
285			for (i = 0; i != len; i++) {
286				char c;
287				if (get_user(c, data + i))
288					return -EFAULT;
289				if (c == 'V')
290					expect_release = 42;
291			}
292		}
293		/* someone wrote to us, we should pat the watchdog */
294		at32_wdt_pat();
295	}
296	return len;
297}
298
299static const struct file_operations at32_wdt_fops = {
300	.owner		= THIS_MODULE,
301	.llseek		= no_llseek,
302	.unlocked_ioctl	= at32_wdt_ioctl,
303	.open		= at32_wdt_open,
304	.release	= at32_wdt_close,
305	.write		= at32_wdt_write,
306};
307
308static int __init at32_wdt_probe(struct platform_device *pdev)
309{
310	struct resource	*regs;
311	int ret;
312
313	if (wdt) {
314		dev_dbg(&pdev->dev, "only 1 wdt instance supported.\n");
315		return -EBUSY;
316	}
317
318	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
319	if (!regs) {
320		dev_dbg(&pdev->dev, "missing mmio resource\n");
321		return -ENXIO;
322	}
323
324	wdt = devm_kzalloc(&pdev->dev, sizeof(struct wdt_at32ap700x),
325			GFP_KERNEL);
326	if (!wdt)
327		return -ENOMEM;
328
329	wdt->regs = devm_ioremap(&pdev->dev, regs->start, resource_size(regs));
330	if (!wdt->regs) {
331		ret = -ENOMEM;
332		dev_dbg(&pdev->dev, "could not map I/O memory\n");
333		goto err_free;
334	}
335
336	spin_lock_init(&wdt->io_lock);
337	wdt->boot_status = at32_wdt_get_status();
338
339	/* Work-around for watchdog silicon errata. */
340	if (wdt->boot_status & WDIOF_CARDRESET) {
341		dev_info(&pdev->dev, "CPU must be reset with external "
342				"reset or POR due to silicon errata.\n");
343		ret = -EIO;
344		goto err_free;
345	} else {
346		wdt->users = 0;
347	}
348
349	wdt->miscdev.minor	= WATCHDOG_MINOR;
350	wdt->miscdev.name	= "watchdog";
351	wdt->miscdev.fops	= &at32_wdt_fops;
352	wdt->miscdev.parent	= &pdev->dev;
353
354	platform_set_drvdata(pdev, wdt);
355
356	if (at32_wdt_settimeout(timeout)) {
357		at32_wdt_settimeout(TIMEOUT_DEFAULT);
358		dev_dbg(&pdev->dev,
359			"default timeout invalid, set to %d sec.\n",
360			TIMEOUT_DEFAULT);
361	}
362
363	ret = misc_register(&wdt->miscdev);
364	if (ret) {
365		dev_dbg(&pdev->dev, "failed to register wdt miscdev\n");
366		goto err_free;
367	}
368
369	dev_info(&pdev->dev,
370		"AT32AP700X WDT at 0x%p, timeout %d sec (nowayout=%d)\n",
371		wdt->regs, wdt->timeout, nowayout);
372
373	return 0;
374
375err_free:
376	wdt = NULL;
377	return ret;
378}
379
380static int __exit at32_wdt_remove(struct platform_device *pdev)
381{
382	if (wdt && platform_get_drvdata(pdev) == wdt) {
383		/* Stop the timer before we leave */
384		if (!nowayout)
385			at32_wdt_stop();
386
387		misc_deregister(&wdt->miscdev);
388		wdt = NULL;
389	}
390	return 0;
391}
392
393static void at32_wdt_shutdown(struct platform_device *pdev)
394{
395	at32_wdt_stop();
396}
397
398#ifdef CONFIG_PM
399static int at32_wdt_suspend(struct platform_device *pdev, pm_message_t message)
400{
401	at32_wdt_stop();
402	return 0;
403}
404
405static int at32_wdt_resume(struct platform_device *pdev)
406{
407	if (wdt->users)
408		at32_wdt_start();
409	return 0;
410}
411#else
412#define at32_wdt_suspend NULL
413#define at32_wdt_resume NULL
414#endif
415
416/* work with hotplug and coldplug */
417MODULE_ALIAS("platform:at32_wdt");
418
419static struct platform_driver at32_wdt_driver = {
420	.remove		= __exit_p(at32_wdt_remove),
421	.suspend	= at32_wdt_suspend,
422	.resume		= at32_wdt_resume,
423	.driver		= {
424		.name	= "at32_wdt",
425	},
426	.shutdown	= at32_wdt_shutdown,
427};
428
429module_platform_driver_probe(at32_wdt_driver, at32_wdt_probe);
430
431MODULE_AUTHOR("Hans-Christian Egtvedt <egtvedt@samfundet.no>");
432MODULE_DESCRIPTION("Watchdog driver for Atmel AT32AP700X");
433MODULE_LICENSE("GPL");
434