1/*
2 *  This program is free software; you can redistribute it and/or modify it
3 *  under the terms of the GNU General Public License version 2 as published
4 *  by the Free Software Foundation.
5 *
6 *  Copyright (C) 2010 John Crispin <blogic@openwrt.org>
7 *  Based on EP93xx wdt driver
8 */
9
10#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11
12#include <linux/module.h>
13#include <linux/fs.h>
14#include <linux/miscdevice.h>
15#include <linux/watchdog.h>
16#include <linux/of_platform.h>
17#include <linux/uaccess.h>
18#include <linux/clk.h>
19#include <linux/io.h>
20
21#include <lantiq_soc.h>
22
23/*
24 * Section 3.4 of the datasheet
25 * The password sequence protects the WDT control register from unintended
26 * write actions, which might cause malfunction of the WDT.
27 *
28 * essentially the following two magic passwords need to be written to allow
29 * IO access to the WDT core
30 */
31#define LTQ_WDT_PW1		0x00BE0000
32#define LTQ_WDT_PW2		0x00DC0000
33
34#define LTQ_WDT_CR		0x0	/* watchdog control register */
35#define LTQ_WDT_SR		0x8	/* watchdog status register */
36
37#define LTQ_WDT_SR_EN		(0x1 << 31)	/* enable bit */
38#define LTQ_WDT_SR_PWD		(0x3 << 26)	/* turn on power */
39#define LTQ_WDT_SR_CLKDIV	(0x3 << 24)	/* turn on clock and set */
40						/* divider to 0x40000 */
41#define LTQ_WDT_DIVIDER		0x40000
42#define LTQ_MAX_TIMEOUT		((1 << 16) - 1)	/* the reload field is 16 bit */
43
44static bool nowayout = WATCHDOG_NOWAYOUT;
45
46static void __iomem *ltq_wdt_membase;
47static unsigned long ltq_io_region_clk_rate;
48
49static unsigned long ltq_wdt_bootstatus;
50static unsigned long ltq_wdt_in_use;
51static int ltq_wdt_timeout = 30;
52static int ltq_wdt_ok_to_close;
53
54static void
55ltq_wdt_enable(void)
56{
57	unsigned long int timeout = ltq_wdt_timeout *
58			(ltq_io_region_clk_rate / LTQ_WDT_DIVIDER) + 0x1000;
59	if (timeout > LTQ_MAX_TIMEOUT)
60		timeout = LTQ_MAX_TIMEOUT;
61
62	/* write the first password magic */
63	ltq_w32(LTQ_WDT_PW1, ltq_wdt_membase + LTQ_WDT_CR);
64	/* write the second magic plus the configuration and new timeout */
65	ltq_w32(LTQ_WDT_SR_EN | LTQ_WDT_SR_PWD | LTQ_WDT_SR_CLKDIV |
66		LTQ_WDT_PW2 | timeout, ltq_wdt_membase + LTQ_WDT_CR);
67}
68
69static void
70ltq_wdt_disable(void)
71{
72	/* write the first password magic */
73	ltq_w32(LTQ_WDT_PW1, ltq_wdt_membase + LTQ_WDT_CR);
74	/*
75	 * write the second password magic with no config
76	 * this turns the watchdog off
77	 */
78	ltq_w32(LTQ_WDT_PW2, ltq_wdt_membase + LTQ_WDT_CR);
79}
80
81static ssize_t
82ltq_wdt_write(struct file *file, const char __user *data,
83		size_t len, loff_t *ppos)
84{
85	if (len) {
86		if (!nowayout) {
87			size_t i;
88
89			ltq_wdt_ok_to_close = 0;
90			for (i = 0; i != len; i++) {
91				char c;
92
93				if (get_user(c, data + i))
94					return -EFAULT;
95				if (c == 'V')
96					ltq_wdt_ok_to_close = 1;
97				else
98					ltq_wdt_ok_to_close = 0;
99			}
100		}
101		ltq_wdt_enable();
102	}
103
104	return len;
105}
106
107static struct watchdog_info ident = {
108	.options = WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
109			WDIOF_CARDRESET,
110	.identity = "ltq_wdt",
111};
112
113static long
114ltq_wdt_ioctl(struct file *file,
115		unsigned int cmd, unsigned long arg)
116{
117	int ret = -ENOTTY;
118
119	switch (cmd) {
120	case WDIOC_GETSUPPORT:
121		ret = copy_to_user((struct watchdog_info __user *)arg, &ident,
122				sizeof(ident)) ? -EFAULT : 0;
123		break;
124
125	case WDIOC_GETBOOTSTATUS:
126		ret = put_user(ltq_wdt_bootstatus, (int __user *)arg);
127		break;
128
129	case WDIOC_GETSTATUS:
130		ret = put_user(0, (int __user *)arg);
131		break;
132
133	case WDIOC_SETTIMEOUT:
134		ret = get_user(ltq_wdt_timeout, (int __user *)arg);
135		if (!ret)
136			ltq_wdt_enable();
137		/* intentional drop through */
138	case WDIOC_GETTIMEOUT:
139		ret = put_user(ltq_wdt_timeout, (int __user *)arg);
140		break;
141
142	case WDIOC_KEEPALIVE:
143		ltq_wdt_enable();
144		ret = 0;
145		break;
146	}
147	return ret;
148}
149
150static int
151ltq_wdt_open(struct inode *inode, struct file *file)
152{
153	if (test_and_set_bit(0, &ltq_wdt_in_use))
154		return -EBUSY;
155	ltq_wdt_in_use = 1;
156	ltq_wdt_enable();
157
158	return nonseekable_open(inode, file);
159}
160
161static int
162ltq_wdt_release(struct inode *inode, struct file *file)
163{
164	if (ltq_wdt_ok_to_close)
165		ltq_wdt_disable();
166	else
167		pr_err("watchdog closed without warning\n");
168	ltq_wdt_ok_to_close = 0;
169	clear_bit(0, &ltq_wdt_in_use);
170
171	return 0;
172}
173
174static const struct file_operations ltq_wdt_fops = {
175	.owner		= THIS_MODULE,
176	.write		= ltq_wdt_write,
177	.unlocked_ioctl	= ltq_wdt_ioctl,
178	.open		= ltq_wdt_open,
179	.release	= ltq_wdt_release,
180	.llseek		= no_llseek,
181};
182
183static struct miscdevice ltq_wdt_miscdev = {
184	.minor	= WATCHDOG_MINOR,
185	.name	= "watchdog",
186	.fops	= &ltq_wdt_fops,
187};
188
189static int
190ltq_wdt_probe(struct platform_device *pdev)
191{
192	struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
193	struct clk *clk;
194
195	ltq_wdt_membase = devm_ioremap_resource(&pdev->dev, res);
196	if (IS_ERR(ltq_wdt_membase))
197		return PTR_ERR(ltq_wdt_membase);
198
199	/* we do not need to enable the clock as it is always running */
200	clk = clk_get_io();
201	if (IS_ERR(clk)) {
202		dev_err(&pdev->dev, "Failed to get clock\n");
203		return -ENOENT;
204	}
205	ltq_io_region_clk_rate = clk_get_rate(clk);
206	clk_put(clk);
207
208	/* find out if the watchdog caused the last reboot */
209	if (ltq_reset_cause() == LTQ_RST_CAUSE_WDTRST)
210		ltq_wdt_bootstatus = WDIOF_CARDRESET;
211
212	dev_info(&pdev->dev, "Init done\n");
213	return misc_register(&ltq_wdt_miscdev);
214}
215
216static int
217ltq_wdt_remove(struct platform_device *pdev)
218{
219	misc_deregister(&ltq_wdt_miscdev);
220
221	return 0;
222}
223
224static const struct of_device_id ltq_wdt_match[] = {
225	{ .compatible = "lantiq,wdt" },
226	{},
227};
228MODULE_DEVICE_TABLE(of, ltq_wdt_match);
229
230static struct platform_driver ltq_wdt_driver = {
231	.probe = ltq_wdt_probe,
232	.remove = ltq_wdt_remove,
233	.driver = {
234		.name = "wdt",
235		.of_match_table = ltq_wdt_match,
236	},
237};
238
239module_platform_driver(ltq_wdt_driver);
240
241module_param(nowayout, bool, 0);
242MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started");
243MODULE_AUTHOR("John Crispin <blogic@openwrt.org>");
244MODULE_DESCRIPTION("Lantiq SoC Watchdog");
245MODULE_LICENSE("GPL");
246