Free Electrons

Embedded Linux Experts

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
/*
 * Watchdog driver for Atmel AT32AP700X devices
 *
 * Copyright (C) 2005-2006 Atmel Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 *
 * Errata: WDT Clear is blocked after WDT Reset
 *
 * A watchdog timer event will, after reset, block writes to the WDT_CLEAR
 * register, preventing the program to clear the next Watchdog Timer Reset.
 *
 * If you still want to use the WDT after a WDT reset a small code can be
 * insterted at the startup checking the AVR32_PM.rcause register for WDT reset
 * and use a GPIO pin to reset the system. This method requires that one of the
 * GPIO pins are available and connected externally to the RESET_N pin. After
 * the GPIO pin has pulled down the reset line the GPIO will be reset and leave
 * the pin tristated with pullup.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>
#include <linux/platform_device.h>
#include <linux/watchdog.h>
#include <linux/uaccess.h>
#include <linux/io.h>
#include <linux/spinlock.h>
#include <linux/slab.h>

#define TIMEOUT_MIN		1
#define TIMEOUT_MAX		2
#define TIMEOUT_DEFAULT		TIMEOUT_MAX

/* module parameters */
static int timeout =  TIMEOUT_DEFAULT;
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout,
		"Timeout value. Limited to be 1 or 2 seconds. (default="
		__MODULE_STRING(TIMEOUT_DEFAULT) ")");

static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
		__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

/* Watchdog registers and write/read macro */
#define WDT_CTRL		0x00
#define WDT_CTRL_EN		   0
#define WDT_CTRL_PSEL		   8
#define WDT_CTRL_KEY		  24

#define WDT_CLR			0x04

#define WDT_RCAUSE		0x10
#define WDT_RCAUSE_POR		   0
#define WDT_RCAUSE_EXT		   2
#define WDT_RCAUSE_WDT		   3
#define WDT_RCAUSE_JTAG		   4
#define WDT_RCAUSE_SERP		   5

#define WDT_BIT(name)		(1 << WDT_##name)
#define WDT_BF(name, value)	((value) << WDT_##name)

#define wdt_readl(dev, reg)				\
	__raw_readl((dev)->regs + WDT_##reg)
#define wdt_writel(dev, reg, value)			\
	__raw_writel((value), (dev)->regs + WDT_##reg)

struct wdt_at32ap700x {
	void __iomem		*regs;
	spinlock_t		io_lock;
	int			timeout;
	int			boot_status;
	unsigned long		users;
	struct miscdevice	miscdev;
};

static struct wdt_at32ap700x *wdt;
static char expect_release;

/*
 * Disable the watchdog.
 */
static inline void at32_wdt_stop(void)
{
	unsigned long psel;

	spin_lock(&wdt->io_lock);
	psel = wdt_readl(wdt, CTRL) & WDT_BF(CTRL_PSEL, 0x0f);
	wdt_writel(wdt, CTRL, psel | WDT_BF(CTRL_KEY, 0x55));
	wdt_writel(wdt, CTRL, psel | WDT_BF(CTRL_KEY, 0xaa));
	spin_unlock(&wdt->io_lock);
}

/*
 * Enable and reset the watchdog.
 */
static inline void at32_wdt_start(void)
{
	/* 0xf is 2^16 divider = 2 sec, 0xe is 2^15 divider = 1 sec */
	unsigned long psel = (wdt->timeout > 1) ? 0xf : 0xe;

	spin_lock(&wdt->io_lock);
	wdt_writel(wdt, CTRL, WDT_BIT(CTRL_EN)
			| WDT_BF(CTRL_PSEL, psel)
			| WDT_BF(CTRL_KEY, 0x55));
	wdt_writel(wdt, CTRL, WDT_BIT(CTRL_EN)
			| WDT_BF(CTRL_PSEL, psel)
			| WDT_BF(CTRL_KEY, 0xaa));
	spin_unlock(&wdt->io_lock);
}

/*
 * Pat the watchdog timer.
 */
static inline void at32_wdt_pat(void)
{
	spin_lock(&wdt->io_lock);
	wdt_writel(wdt, CLR, 0x42);
	spin_unlock(&wdt->io_lock);
}

/*
 * Watchdog device is opened, and watchdog starts running.
 */
static int at32_wdt_open(struct inode *inode, struct file *file)
{
	if (test_and_set_bit(1, &wdt->users))
		return -EBUSY;

	at32_wdt_start();
	return nonseekable_open(inode, file);
}

/*
 * Close the watchdog device.
 */
static int at32_wdt_close(struct inode *inode, struct file *file)
{
	if (expect_release == 42) {
		at32_wdt_stop();
	} else {
		dev_dbg(wdt->miscdev.parent,
			"unexpected close, not stopping watchdog!\n");
		at32_wdt_pat();
	}
	clear_bit(1, &wdt->users);
	expect_release = 0;
	return 0;
}

/*
 * Change the watchdog time interval.
 */
static int at32_wdt_settimeout(int time)
{
	/*
	 * All counting occurs at 1 / SLOW_CLOCK (32 kHz) and max prescaler is
	 * 2 ^ 16 allowing up to 2 seconds timeout.
	 */
	if ((time < TIMEOUT_MIN) || (time > TIMEOUT_MAX))
		return -EINVAL;

	/*
	 * Set new watchdog time. It will be used when at32_wdt_start() is
	 * called.
	 */
	wdt->timeout = time;
	return 0;
}

/*
 * Get the watchdog status.
 */
static int at32_wdt_get_status(void)
{
	int rcause;
	int status = 0;

	rcause = wdt_readl(wdt, RCAUSE);

	switch (rcause) {
	case WDT_BIT(RCAUSE_EXT):
		status = WDIOF_EXTERN1;
		break;
	case WDT_BIT(RCAUSE_WDT):
		status = WDIOF_CARDRESET;
		break;
	case WDT_BIT(RCAUSE_POR):  /* fall through */
	case WDT_BIT(RCAUSE_JTAG): /* fall through */
	case WDT_BIT(RCAUSE_SERP): /* fall through */
	default:
		break;
	}

	return status;
}

static const struct watchdog_info at32_wdt_info = {
	.identity	= "at32ap700x watchdog",
	.options	= WDIOF_SETTIMEOUT |
			  WDIOF_KEEPALIVEPING |
			  WDIOF_MAGICCLOSE,
};

/*
 * Handle commands from user-space.
 */
static long at32_wdt_ioctl(struct file *file,
				unsigned int cmd, unsigned long arg)
{
	int ret = -ENOTTY;
	int time;
	void __user *argp = (void __user *)arg;
	int __user *p = argp;

	switch (cmd) {
	case WDIOC_GETSUPPORT:
		ret = copy_to_user(argp, &at32_wdt_info,
				sizeof(at32_wdt_info)) ? -EFAULT : 0;
		break;
	case WDIOC_GETSTATUS:
		ret = put_user(0, p);
		break;
	case WDIOC_GETBOOTSTATUS:
		ret = put_user(wdt->boot_status, p);
		break;
	case WDIOC_SETOPTIONS:
		ret = get_user(time, p);
		if (ret)
			break;
		if (time & WDIOS_DISABLECARD)
			at32_wdt_stop();
		if (time & WDIOS_ENABLECARD)
			at32_wdt_start();
		ret = 0;
		break;
	case WDIOC_KEEPALIVE:
		at32_wdt_pat();
		ret = 0;
		break;
	case WDIOC_SETTIMEOUT:
		ret = get_user(time, p);
		if (ret)
			break;
		ret = at32_wdt_settimeout(time);
		if (ret)
			break;
		/* Enable new time value */
		at32_wdt_start();
		/* fall through */
	case WDIOC_GETTIMEOUT:
		ret = put_user(wdt->timeout, p);
		break;
	}

	return ret;
}

static ssize_t at32_wdt_write(struct file *file, const char __user *data,
				size_t len, loff_t *ppos)
{
	/* See if we got the magic character 'V' and reload the timer */
	if (len) {
		if (!nowayout) {
			size_t i;

			/*
			 * note: just in case someone wrote the magic
			 * character five months ago...
			 */
			expect_release = 0;

			/*
			 * scan to see whether or not we got the magic
			 * character
			 */
			for (i = 0; i != len; i++) {
				char c;
				if (get_user(c, data + i))
					return -EFAULT;
				if (c == 'V')
					expect_release = 42;
			}
		}
		/* someone wrote to us, we should pat the watchdog */
		at32_wdt_pat();
	}
	return len;
}

static const struct file_operations at32_wdt_fops = {
	.owner		= THIS_MODULE,
	.llseek		= no_llseek,
	.unlocked_ioctl	= at32_wdt_ioctl,
	.open		= at32_wdt_open,
	.release	= at32_wdt_close,
	.write		= at32_wdt_write,
};

static int __init at32_wdt_probe(struct platform_device *pdev)
{
	struct resource	*regs;
	int ret;

	if (wdt) {
		dev_dbg(&pdev->dev, "only 1 wdt instance supported.\n");
		return -EBUSY;
	}

	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!regs) {
		dev_dbg(&pdev->dev, "missing mmio resource\n");
		return -ENXIO;
	}

	wdt = devm_kzalloc(&pdev->dev, sizeof(struct wdt_at32ap700x),
			GFP_KERNEL);
	if (!wdt)
		return -ENOMEM;

	wdt->regs = devm_ioremap(&pdev->dev, regs->start, resource_size(regs));
	if (!wdt->regs) {
		ret = -ENOMEM;
		dev_dbg(&pdev->dev, "could not map I/O memory\n");
		goto err_free;
	}

	spin_lock_init(&wdt->io_lock);
	wdt->boot_status = at32_wdt_get_status();

	/* Work-around for watchdog silicon errata. */
	if (wdt->boot_status & WDIOF_CARDRESET) {
		dev_info(&pdev->dev, "CPU must be reset with external "
				"reset or POR due to silicon errata.\n");
		ret = -EIO;
		goto err_free;
	} else {
		wdt->users = 0;
	}

	wdt->miscdev.minor	= WATCHDOG_MINOR;
	wdt->miscdev.name	= "watchdog";
	wdt->miscdev.fops	= &at32_wdt_fops;
	wdt->miscdev.parent	= &pdev->dev;

	platform_set_drvdata(pdev, wdt);

	if (at32_wdt_settimeout(timeout)) {
		at32_wdt_settimeout(TIMEOUT_DEFAULT);
		dev_dbg(&pdev->dev,
			"default timeout invalid, set to %d sec.\n",
			TIMEOUT_DEFAULT);
	}

	ret = misc_register(&wdt->miscdev);
	if (ret) {
		dev_dbg(&pdev->dev, "failed to register wdt miscdev\n");
		goto err_free;
	}

	dev_info(&pdev->dev,
		"AT32AP700X WDT at 0x%p, timeout %d sec (nowayout=%d)\n",
		wdt->regs, wdt->timeout, nowayout);

	return 0;

err_free:
	wdt = NULL;
	return ret;
}

static int __exit at32_wdt_remove(struct platform_device *pdev)
{
	if (wdt && platform_get_drvdata(pdev) == wdt) {
		/* Stop the timer before we leave */
		if (!nowayout)
			at32_wdt_stop();

		misc_deregister(&wdt->miscdev);
		wdt = NULL;
	}
	return 0;
}

static void at32_wdt_shutdown(struct platform_device *pdev)
{
	at32_wdt_stop();
}

#ifdef CONFIG_PM
static int at32_wdt_suspend(struct platform_device *pdev, pm_message_t message)
{
	at32_wdt_stop();
	return 0;
}

static int at32_wdt_resume(struct platform_device *pdev)
{
	if (wdt->users)
		at32_wdt_start();
	return 0;
}
#else
#define at32_wdt_suspend NULL
#define at32_wdt_resume NULL
#endif

/* work with hotplug and coldplug */
MODULE_ALIAS("platform:at32_wdt");

static struct platform_driver at32_wdt_driver = {
	.remove		= __exit_p(at32_wdt_remove),
	.suspend	= at32_wdt_suspend,
	.resume		= at32_wdt_resume,
	.driver		= {
		.name	= "at32_wdt",
	},
	.shutdown	= at32_wdt_shutdown,
};

module_platform_driver_probe(at32_wdt_driver, at32_wdt_probe);

MODULE_AUTHOR("Hans-Christian Egtvedt <egtvedt@samfundet.no>");
MODULE_DESCRIPTION("Watchdog driver for Atmel AT32AP700X");
MODULE_LICENSE("GPL");