1/*
  2 * drivers/watchdog/ar7_wdt.c
  3 *
  4 * Copyright (C) 2007 Nicolas Thill <nico@openwrt.org>
  5 * Copyright (c) 2005 Enrik Berkhan <Enrik.Berkhan@akk.org>
  6 *
  7 * Some code taken from:
  8 * National Semiconductor SCx200 Watchdog support
  9 * Copyright (c) 2001,2002 Christer Weinigel <wingel@nano-system.com>
 10 *
 11 * This program is free software; you can redistribute it and/or modify
 12 * it under the terms of the GNU General Public License as published by
 13 * the Free Software Foundation; either version 2 of the License, or
 14 * (at your option) any later version.
 15 *
 16 * This program is distributed in the hope that it will be useful,
 17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 19 * GNU General Public License for more details.
 20 *
 21 * You should have received a copy of the GNU General Public License
 22 * along with this program; if not, write to the Free Software
 23 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 24 */
 25
 26#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 27
 28#include <linux/module.h>
 29#include <linux/moduleparam.h>
 30#include <linux/errno.h>
 31#include <linux/miscdevice.h>
 32#include <linux/platform_device.h>
 33#include <linux/watchdog.h>
 34#include <linux/fs.h>
 35#include <linux/ioport.h>
 36#include <linux/io.h>
 37#include <linux/uaccess.h>
 38#include <linux/clk.h>
 39
 40#include <asm/addrspace.h>
 41#include <asm/mach-ar7/ar7.h>
 42
 43#define LONGNAME "TI AR7 Watchdog Timer"
 44
 45MODULE_AUTHOR("Nicolas Thill <nico@openwrt.org>");
 46MODULE_DESCRIPTION(LONGNAME);
 47MODULE_LICENSE("GPL");
 48
 49static int margin = 60;
 50module_param(margin, int, 0);
 51MODULE_PARM_DESC(margin, "Watchdog margin in seconds");
 52
 53static bool nowayout = WATCHDOG_NOWAYOUT;
 54module_param(nowayout, bool, 0);
 55MODULE_PARM_DESC(nowayout, "Disable watchdog shutdown on close");
 56
 57#define READ_REG(x) readl((void __iomem *)&(x))
 58#define WRITE_REG(x, v) writel((v), (void __iomem *)&(x))
 59
 60struct ar7_wdt {
 61	u32 kick_lock;
 62	u32 kick;
 63	u32 change_lock;
 64	u32 change;
 65	u32 disable_lock;
 66	u32 disable;
 67	u32 prescale_lock;
 68	u32 prescale;
 69};
 70
 71static unsigned long wdt_is_open;
 72static unsigned expect_close;
 73static DEFINE_SPINLOCK(wdt_lock);
 74
 75/* XXX currently fixed, allows max margin ~68.72 secs */
 76#define prescale_value 0xffff
 77
 78/* Resource of the WDT registers */
 79static struct resource *ar7_regs_wdt;
 80/* Pointer to the remapped WDT IO space */
 81static struct ar7_wdt *ar7_wdt;
 82
 83static struct clk *vbus_clk;
 84
 85static void ar7_wdt_kick(u32 value)
 86{
 87	WRITE_REG(ar7_wdt->kick_lock, 0x5555);
 88	if ((READ_REG(ar7_wdt->kick_lock) & 3) == 1) {
 89		WRITE_REG(ar7_wdt->kick_lock, 0xaaaa);
 90		if ((READ_REG(ar7_wdt->kick_lock) & 3) == 3) {
 91			WRITE_REG(ar7_wdt->kick, value);
 92			return;
 93		}
 94	}
 95	pr_err("failed to unlock WDT kick reg\n");
 96}
 97
 98static void ar7_wdt_prescale(u32 value)
 99{
100	WRITE_REG(ar7_wdt->prescale_lock, 0x5a5a);
101	if ((READ_REG(ar7_wdt->prescale_lock) & 3) == 1) {
102		WRITE_REG(ar7_wdt->prescale_lock, 0xa5a5);
103		if ((READ_REG(ar7_wdt->prescale_lock) & 3) == 3) {
104			WRITE_REG(ar7_wdt->prescale, value);
105			return;
106		}
107	}
108	pr_err("failed to unlock WDT prescale reg\n");
109}
110
111static void ar7_wdt_change(u32 value)
112{
113	WRITE_REG(ar7_wdt->change_lock, 0x6666);
114	if ((READ_REG(ar7_wdt->change_lock) & 3) == 1) {
115		WRITE_REG(ar7_wdt->change_lock, 0xbbbb);
116		if ((READ_REG(ar7_wdt->change_lock) & 3) == 3) {
117			WRITE_REG(ar7_wdt->change, value);
118			return;
119		}
120	}
121	pr_err("failed to unlock WDT change reg\n");
122}
123
124static void ar7_wdt_disable(u32 value)
125{
126	WRITE_REG(ar7_wdt->disable_lock, 0x7777);
127	if ((READ_REG(ar7_wdt->disable_lock) & 3) == 1) {
128		WRITE_REG(ar7_wdt->disable_lock, 0xcccc);
129		if ((READ_REG(ar7_wdt->disable_lock) & 3) == 2) {
130			WRITE_REG(ar7_wdt->disable_lock, 0xdddd);
131			if ((READ_REG(ar7_wdt->disable_lock) & 3) == 3) {
132				WRITE_REG(ar7_wdt->disable, value);
133				return;
134			}
135		}
136	}
137	pr_err("failed to unlock WDT disable reg\n");
138}
139
140static void ar7_wdt_update_margin(int new_margin)
141{
142	u32 change;
143	u32 vbus_rate;
144
145	vbus_rate = clk_get_rate(vbus_clk);
146	change = new_margin * (vbus_rate / prescale_value);
147	if (change < 1)
148		change = 1;
149	if (change > 0xffff)
150		change = 0xffff;
151	ar7_wdt_change(change);
152	margin = change * prescale_value / vbus_rate;
153	pr_info("timer margin %d seconds (prescale %d, change %d, freq %d)\n",
154		margin, prescale_value, change, vbus_rate);
155}
156
157static void ar7_wdt_enable_wdt(void)
158{
159	pr_debug("enabling watchdog timer\n");
160	ar7_wdt_disable(1);
161	ar7_wdt_kick(1);
162}
163
164static void ar7_wdt_disable_wdt(void)
165{
166	pr_debug("disabling watchdog timer\n");
167	ar7_wdt_disable(0);
168}
169
170static int ar7_wdt_open(struct inode *inode, struct file *file)
171{
172	/* only allow one at a time */
173	if (test_and_set_bit(0, &wdt_is_open))
174		return -EBUSY;
175	ar7_wdt_enable_wdt();
176	expect_close = 0;
177
178	return nonseekable_open(inode, file);
179}
180
181static int ar7_wdt_release(struct inode *inode, struct file *file)
182{
183	if (!expect_close)
184		pr_warn("watchdog device closed unexpectedly, will not disable the watchdog timer\n");
185	else if (!nowayout)
186		ar7_wdt_disable_wdt();
187	clear_bit(0, &wdt_is_open);
188	return 0;
189}
190
191static ssize_t ar7_wdt_write(struct file *file, const char *data,
192			     size_t len, loff_t *ppos)
193{
194	/* check for a magic close character */
195	if (len) {
196		size_t i;
197
198		spin_lock(&wdt_lock);
199		ar7_wdt_kick(1);
200		spin_unlock(&wdt_lock);
201
202		expect_close = 0;
203		for (i = 0; i < len; ++i) {
204			char c;
205			if (get_user(c, data + i))
206				return -EFAULT;
207			if (c == 'V')
208				expect_close = 1;
209		}
210
211	}
212	return len;
213}
214
215static long ar7_wdt_ioctl(struct file *file,
216					unsigned int cmd, unsigned long arg)
217{
218	static const struct watchdog_info ident = {
219		.identity = LONGNAME,
220		.firmware_version = 1,
221		.options = (WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
222						WDIOF_MAGICCLOSE),
223	};
224	int new_margin;
225
226	switch (cmd) {
227	case WDIOC_GETSUPPORT:
228		if (copy_to_user((struct watchdog_info *)arg, &ident,
229				sizeof(ident)))
230			return -EFAULT;
231		return 0;
232	case WDIOC_GETSTATUS:
233	case WDIOC_GETBOOTSTATUS:
234		if (put_user(0, (int *)arg))
235			return -EFAULT;
236		return 0;
237	case WDIOC_KEEPALIVE:
238		ar7_wdt_kick(1);
239		return 0;
240	case WDIOC_SETTIMEOUT:
241		if (get_user(new_margin, (int *)arg))
242			return -EFAULT;
243		if (new_margin < 1)
244			return -EINVAL;
245
246		spin_lock(&wdt_lock);
247		ar7_wdt_update_margin(new_margin);
248		ar7_wdt_kick(1);
249		spin_unlock(&wdt_lock);
250
251	case WDIOC_GETTIMEOUT:
252		if (put_user(margin, (int *)arg))
253			return -EFAULT;
254		return 0;
255	default:
256		return -ENOTTY;
257	}
258}
259
260static const struct file_operations ar7_wdt_fops = {
261	.owner		= THIS_MODULE,
262	.write		= ar7_wdt_write,
263	.unlocked_ioctl	= ar7_wdt_ioctl,
264	.open		= ar7_wdt_open,
265	.release	= ar7_wdt_release,
266	.llseek		= no_llseek,
267};
268
269static struct miscdevice ar7_wdt_miscdev = {
270	.minor		= WATCHDOG_MINOR,
271	.name		= "watchdog",
272	.fops		= &ar7_wdt_fops,
273};
274
275static int ar7_wdt_probe(struct platform_device *pdev)
276{
277	int rc;
278
279	ar7_regs_wdt =
280		platform_get_resource_byname(pdev, IORESOURCE_MEM, "regs");
281	ar7_wdt = devm_ioremap_resource(&pdev->dev, ar7_regs_wdt);
282	if (IS_ERR(ar7_wdt))
283		return PTR_ERR(ar7_wdt);
284
285	vbus_clk = clk_get(NULL, "vbus");
286	if (IS_ERR(vbus_clk)) {
287		pr_err("could not get vbus clock\n");
288		return PTR_ERR(vbus_clk);
289	}
290
291	ar7_wdt_disable_wdt();
292	ar7_wdt_prescale(prescale_value);
293	ar7_wdt_update_margin(margin);
294
295	rc = misc_register(&ar7_wdt_miscdev);
296	if (rc) {
297		pr_err("unable to register misc device\n");
298		goto out;
299	}
300	return 0;
301
302out:
303	clk_put(vbus_clk);
304	vbus_clk = NULL;
305	return rc;
306}
307
308static int ar7_wdt_remove(struct platform_device *pdev)
309{
310	misc_deregister(&ar7_wdt_miscdev);
311	clk_put(vbus_clk);
312	vbus_clk = NULL;
313	return 0;
314}
315
316static void ar7_wdt_shutdown(struct platform_device *pdev)
317{
318	if (!nowayout)
319		ar7_wdt_disable_wdt();
320}
321
322static struct platform_driver ar7_wdt_driver = {
323	.probe = ar7_wdt_probe,
324	.remove = ar7_wdt_remove,
325	.shutdown = ar7_wdt_shutdown,
326	.driver = {
327		.owner = THIS_MODULE,
328		.name = "ar7_wdt",
329	},
330};
331
332module_platform_driver(ar7_wdt_driver);