dw_wdt.c 9.49 KB
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
/*
 * Copyright 2010-2011 Picochip Ltd., Jamie Iles
 * http://www.picochip.com
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 *
 * This file implements a driver for the Synopsys DesignWare watchdog device
 * in the many subsystems. The watchdog has 16 different timeout periods
 * and these are a function of the input clock frequency.
 *
 * The DesignWare watchdog cannot be stopped once it has been started so we
 * use a software timer to implement a ping that will keep the watchdog alive.
 * If we receive an expected close for the watchdog then we keep the timer
 * running, otherwise the timer is stopped and the watchdog will expire.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/bitops.h>
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/fs.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/notifier.h>
#include <linux/of.h>
#include <linux/pm.h>
#include <linux/platform_device.h>
#include <linux/reboot.h>
#include <linux/timer.h>
#include <linux/uaccess.h>
#include <linux/watchdog.h>

#define WDOG_CONTROL_REG_OFFSET		    0x00
#define WDOG_CONTROL_REG_WDT_EN_MASK	    0x01
#define WDOG_TIMEOUT_RANGE_REG_OFFSET	    0x04
#define WDOG_TIMEOUT_RANGE_TOPINIT_SHIFT    4
#define WDOG_CURRENT_COUNT_REG_OFFSET	    0x08
#define WDOG_COUNTER_RESTART_REG_OFFSET     0x0c
#define WDOG_COUNTER_RESTART_KICK_VALUE	    0x76

/* The maximum TOP (timeout period) value that can be set in the watchdog. */
#define DW_WDT_MAX_TOP		15

#define DW_WDT_DEFAULT_SECONDS	30

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) ")");

#define WDT_TIMEOUT		(HZ / 2)

static struct {
	void __iomem		*regs;
	struct clk		*clk;
	unsigned long		in_use;
	unsigned long		next_heartbeat;
	struct timer_list	timer;
	int			expect_close;
	struct notifier_block	restart_handler;
} dw_wdt;

static inline int dw_wdt_is_enabled(void)
{
	return readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET) &
		WDOG_CONTROL_REG_WDT_EN_MASK;
}

static inline int dw_wdt_top_in_seconds(unsigned top)
{
	/*
	 * There are 16 possible timeout values in 0..15 where the number of
	 * cycles is 2 ^ (16 + i) and the watchdog counts down.
	 */
	return (1 << (16 + top)) / clk_get_rate(dw_wdt.clk);
}

static int dw_wdt_get_top(void)
{
	int top = readl(dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET) & 0xF;

	return dw_wdt_top_in_seconds(top);
}

static inline void dw_wdt_set_next_heartbeat(void)
{
	dw_wdt.next_heartbeat = jiffies + dw_wdt_get_top() * HZ;
}

static void dw_wdt_keepalive(void)
{
	writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
	       WDOG_COUNTER_RESTART_REG_OFFSET);
}

static int dw_wdt_set_top(unsigned top_s)
{
	int i, top_val = DW_WDT_MAX_TOP;

	/*
	 * Iterate over the timeout values until we find the closest match. We
	 * always look for >=.
	 */
	for (i = 0; i <= DW_WDT_MAX_TOP; ++i)
		if (dw_wdt_top_in_seconds(i) >= top_s) {
			top_val = i;
			break;
		}

	/*
	 * Set the new value in the watchdog.  Some versions of dw_wdt
	 * have have TOPINIT in the TIMEOUT_RANGE register (as per
	 * CP_WDT_DUAL_TOP in WDT_COMP_PARAMS_1).  On those we
	 * effectively get a pat of the watchdog right here.
	 */
	writel(top_val | top_val << WDOG_TIMEOUT_RANGE_TOPINIT_SHIFT,
		dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);

	/*
	 * Add an explicit pat to handle versions of the watchdog that
	 * don't have TOPINIT.  This won't hurt on versions that have
	 * it.
	 */
	dw_wdt_keepalive();

	dw_wdt_set_next_heartbeat();

	return dw_wdt_top_in_seconds(top_val);
}

static int dw_wdt_restart_handle(struct notifier_block *this,
				unsigned long mode, void *cmd)
{
	u32 val;

	writel(0, dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);
	val = readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
	if (val & WDOG_CONTROL_REG_WDT_EN_MASK)
		writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
			WDOG_COUNTER_RESTART_REG_OFFSET);
	else
		writel(WDOG_CONTROL_REG_WDT_EN_MASK,
		       dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);

	/* wait for reset to assert... */
	mdelay(500);

	return NOTIFY_DONE;
}

static void dw_wdt_ping(unsigned long data)
{
	if (time_before(jiffies, dw_wdt.next_heartbeat) ||
	    (!nowayout && !dw_wdt.in_use)) {
		dw_wdt_keepalive();
		mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
	} else
		pr_crit("keepalive missed, machine will reset\n");
}

static int dw_wdt_open(struct inode *inode, struct file *filp)
{
	if (test_and_set_bit(0, &dw_wdt.in_use))
		return -EBUSY;

	/* Make sure we don't get unloaded. */
	__module_get(THIS_MODULE);

	if (!dw_wdt_is_enabled()) {
		/*
		 * The watchdog is not currently enabled. Set the timeout to
		 * something reasonable and then start it.
		 */
		dw_wdt_set_top(DW_WDT_DEFAULT_SECONDS);
		writel(WDOG_CONTROL_REG_WDT_EN_MASK,
		       dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
	}

	dw_wdt_set_next_heartbeat();

	return nonseekable_open(inode, filp);
}

static ssize_t dw_wdt_write(struct file *filp, const char __user *buf,
			    size_t len, loff_t *offset)
{
	if (!len)
		return 0;

	if (!nowayout) {
		size_t i;

		dw_wdt.expect_close = 0;

		for (i = 0; i < len; ++i) {
			char c;

			if (get_user(c, buf + i))
				return -EFAULT;

			if (c == 'V') {
				dw_wdt.expect_close = 1;
				break;
			}
		}
	}

	dw_wdt_set_next_heartbeat();
	dw_wdt_keepalive();
	mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);

	return len;
}

static u32 dw_wdt_time_left(void)
{
	return readl(dw_wdt.regs + WDOG_CURRENT_COUNT_REG_OFFSET) /
		clk_get_rate(dw_wdt.clk);
}

static const struct watchdog_info dw_wdt_ident = {
	.options	= WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
			  WDIOF_MAGICCLOSE,
	.identity	= "Synopsys DesignWare Watchdog",
};

static long dw_wdt_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
	unsigned long val;
	int timeout;

	switch (cmd) {
	case WDIOC_GETSUPPORT:
		return copy_to_user((void __user *)arg, &dw_wdt_ident,
				    sizeof(dw_wdt_ident)) ? -EFAULT : 0;

	case WDIOC_GETSTATUS:
	case WDIOC_GETBOOTSTATUS:
		return put_user(0, (int __user *)arg);

	case WDIOC_KEEPALIVE:
		dw_wdt_set_next_heartbeat();
		return 0;

	case WDIOC_SETTIMEOUT:
		if (get_user(val, (int __user *)arg))
			return -EFAULT;
		timeout = dw_wdt_set_top(val);
		return put_user(timeout , (int __user *)arg);

	case WDIOC_GETTIMEOUT:
		return put_user(dw_wdt_get_top(), (int __user *)arg);

	case WDIOC_GETTIMELEFT:
		/* Get the time left until expiry. */
		if (get_user(val, (int __user *)arg))
			return -EFAULT;
		return put_user(dw_wdt_time_left(), (int __user *)arg);

	default:
		return -ENOTTY;
	}
}

static int dw_wdt_release(struct inode *inode, struct file *filp)
{
	clear_bit(0, &dw_wdt.in_use);

	if (!dw_wdt.expect_close) {
		del_timer(&dw_wdt.timer);

		if (!nowayout)
			pr_crit("unexpected close, system will reboot soon\n");
		else
			pr_crit("watchdog cannot be disabled, system will reboot soon\n");
	}

	dw_wdt.expect_close = 0;

	return 0;
}

#ifdef CONFIG_PM_SLEEP
static int dw_wdt_suspend(struct device *dev)
{
	clk_disable_unprepare(dw_wdt.clk);

	return 0;
}

static int dw_wdt_resume(struct device *dev)
{
	int err = clk_prepare_enable(dw_wdt.clk);

	if (err)
		return err;

	dw_wdt_keepalive();

	return 0;
}
#endif /* CONFIG_PM_SLEEP */

static SIMPLE_DEV_PM_OPS(dw_wdt_pm_ops, dw_wdt_suspend, dw_wdt_resume);

static const struct file_operations wdt_fops = {
	.owner		= THIS_MODULE,
	.llseek		= no_llseek,
	.open		= dw_wdt_open,
	.write		= dw_wdt_write,
	.unlocked_ioctl	= dw_wdt_ioctl,
	.release	= dw_wdt_release
};

static struct miscdevice dw_wdt_miscdev = {
	.fops		= &wdt_fops,
	.name		= "watchdog",
	.minor		= WATCHDOG_MINOR,
};

static int dw_wdt_drv_probe(struct platform_device *pdev)
{
	int ret;
	struct resource *mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);

	dw_wdt.regs = devm_ioremap_resource(&pdev->dev, mem);
	if (IS_ERR(dw_wdt.regs))
		return PTR_ERR(dw_wdt.regs);

	dw_wdt.clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(dw_wdt.clk))
		return PTR_ERR(dw_wdt.clk);

	ret = clk_prepare_enable(dw_wdt.clk);
	if (ret)
		return ret;

	ret = misc_register(&dw_wdt_miscdev);
	if (ret)
		goto out_disable_clk;

	dw_wdt.restart_handler.notifier_call = dw_wdt_restart_handle;
	dw_wdt.restart_handler.priority = 128;
	ret = register_restart_handler(&dw_wdt.restart_handler);
	if (ret)
		pr_warn("cannot register restart handler\n");

	dw_wdt_set_next_heartbeat();
	setup_timer(&dw_wdt.timer, dw_wdt_ping, 0);
	mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);

	return 0;

out_disable_clk:
	clk_disable_unprepare(dw_wdt.clk);

	return ret;
}

static int dw_wdt_drv_remove(struct platform_device *pdev)
{
	unregister_restart_handler(&dw_wdt.restart_handler);

	misc_deregister(&dw_wdt_miscdev);

	clk_disable_unprepare(dw_wdt.clk);

	return 0;
}

#ifdef CONFIG_OF
static const struct of_device_id dw_wdt_of_match[] = {
	{ .compatible = "snps,dw-wdt", },
	{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, dw_wdt_of_match);
#endif

static struct platform_driver dw_wdt_driver = {
	.probe		= dw_wdt_drv_probe,
	.remove		= dw_wdt_drv_remove,
	.driver		= {
		.name	= "dw_wdt",
		.of_match_table = of_match_ptr(dw_wdt_of_match),
		.pm	= &dw_wdt_pm_ops,
	},
};

module_platform_driver(dw_wdt_driver);

MODULE_AUTHOR("Jamie Iles");
MODULE_DESCRIPTION("Synopsys DesignWare Watchdog Driver");
MODULE_LICENSE("GPL");