1/*
2 * GE watchdog userspace interface
3 *
4 * Author:  Martyn Welch <martyn.welch@ge.com>
5 *
6 * Copyright 2008 GE Intelligent Platforms Embedded Systems, Inc.
7 *
8 * This program is free software; you can redistribute  it and/or modify it
9 * under  the terms of  the GNU General  Public License as published by the
10 * Free Software Foundation;  either version 2 of the  License, or (at your
11 * option) any later version.
12 *
13 * Based on: mv64x60_wdt.c (MV64X60 watchdog userspace interface)
14 *   Author: James Chapman <jchapman@katalix.com>
15 */
16
17/* TODO:
18 * This driver does not provide support for the hardwares capability of sending
19 * an interrupt at a programmable threshold.
20 *
21 * This driver currently can only support 1 watchdog - there are 2 in the
22 * hardware that this driver supports. Thus one could be configured as a
23 * process-based watchdog (via /dev/watchdog), the second (using the interrupt
24 * capabilities) a kernel-based watchdog.
25 */
26
27#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
28
29#include <linux/kernel.h>
30#include <linux/compiler.h>
31#include <linux/init.h>
32#include <linux/module.h>
33#include <linux/miscdevice.h>
34#include <linux/watchdog.h>
35#include <linux/fs.h>
36#include <linux/of.h>
37#include <linux/of_address.h>
38#include <linux/of_platform.h>
39#include <linux/io.h>
40#include <linux/uaccess.h>
41
42#include <sysdev/fsl_soc.h>
43
44/*
45 * The watchdog configuration register contains a pair of 2-bit fields,
46 *   1.  a reload field, bits 27-26, which triggers a reload of
47 *       the countdown register, and
48 *   2.  an enable field, bits 25-24, which toggles between
49 *       enabling and disabling the watchdog timer.
50 * Bit 31 is a read-only field which indicates whether the
51 * watchdog timer is currently enabled.
52 *
53 * The low 24 bits contain the timer reload value.
54 */
55#define GEF_WDC_ENABLE_SHIFT	24
56#define GEF_WDC_SERVICE_SHIFT	26
57#define GEF_WDC_ENABLED_SHIFT	31
58
59#define GEF_WDC_ENABLED_TRUE	1
60#define GEF_WDC_ENABLED_FALSE	0
61
62/* Flags bits */
63#define GEF_WDOG_FLAG_OPENED	0
64
65static unsigned long wdt_flags;
66static int wdt_status;
67static void __iomem *gef_wdt_regs;
68static int gef_wdt_timeout;
69static int gef_wdt_count;
70static unsigned int bus_clk;
71static char expect_close;
72static DEFINE_SPINLOCK(gef_wdt_spinlock);
73
74static bool nowayout = WATCHDOG_NOWAYOUT;
75module_param(nowayout, bool, 0);
76MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
77	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
78
79
80static int gef_wdt_toggle_wdc(int enabled_predicate, int field_shift)
81{
82	u32 data;
83	u32 enabled;
84	int ret = 0;
85
86	spin_lock(&gef_wdt_spinlock);
87	data = ioread32be(gef_wdt_regs);
88	enabled = (data >> GEF_WDC_ENABLED_SHIFT) & 1;
89
90	/* only toggle the requested field if enabled state matches predicate */
91	if ((enabled ^ enabled_predicate) == 0) {
92		/* We write a 1, then a 2 -- to the appropriate field */
93		data = (1 << field_shift) | gef_wdt_count;
94		iowrite32be(data, gef_wdt_regs);
95
96		data = (2 << field_shift) | gef_wdt_count;
97		iowrite32be(data, gef_wdt_regs);
98		ret = 1;
99	}
100	spin_unlock(&gef_wdt_spinlock);
101
102	return ret;
103}
104
105static void gef_wdt_service(void)
106{
107	gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
108		GEF_WDC_SERVICE_SHIFT);
109}
110
111static void gef_wdt_handler_enable(void)
112{
113	if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_FALSE,
114				   GEF_WDC_ENABLE_SHIFT)) {
115		gef_wdt_service();
116		pr_notice("watchdog activated\n");
117	}
118}
119
120static void gef_wdt_handler_disable(void)
121{
122	if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
123				   GEF_WDC_ENABLE_SHIFT))
124		pr_notice("watchdog deactivated\n");
125}
126
127static void gef_wdt_set_timeout(unsigned int timeout)
128{
129	/* maximum bus cycle count is 0xFFFFFFFF */
130	if (timeout > 0xFFFFFFFF / bus_clk)
131		timeout = 0xFFFFFFFF / bus_clk;
132
133	/* Register only holds upper 24 bits, bit shifted into lower 24 */
134	gef_wdt_count = (timeout * bus_clk) >> 8;
135	gef_wdt_timeout = timeout;
136}
137
138
139static ssize_t gef_wdt_write(struct file *file, const char __user *data,
140				 size_t len, loff_t *ppos)
141{
142	if (len) {
143		if (!nowayout) {
144			size_t i;
145
146			expect_close = 0;
147
148			for (i = 0; i != len; i++) {
149				char c;
150				if (get_user(c, data + i))
151					return -EFAULT;
152				if (c == 'V')
153					expect_close = 42;
154			}
155		}
156		gef_wdt_service();
157	}
158
159	return len;
160}
161
162static long gef_wdt_ioctl(struct file *file, unsigned int cmd,
163							unsigned long arg)
164{
165	int timeout;
166	int options;
167	void __user *argp = (void __user *)arg;
168	static const struct watchdog_info info = {
169		.options =	WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
170				WDIOF_KEEPALIVEPING,
171		.firmware_version = 0,
172		.identity = "GE watchdog",
173	};
174
175	switch (cmd) {
176	case WDIOC_GETSUPPORT:
177		if (copy_to_user(argp, &info, sizeof(info)))
178			return -EFAULT;
179		break;
180
181	case WDIOC_GETSTATUS:
182	case WDIOC_GETBOOTSTATUS:
183		if (put_user(wdt_status, (int __user *)argp))
184			return -EFAULT;
185		wdt_status &= ~WDIOF_KEEPALIVEPING;
186		break;
187
188	case WDIOC_SETOPTIONS:
189		if (get_user(options, (int __user *)argp))
190			return -EFAULT;
191
192		if (options & WDIOS_DISABLECARD)
193			gef_wdt_handler_disable();
194
195		if (options & WDIOS_ENABLECARD)
196			gef_wdt_handler_enable();
197		break;
198
199	case WDIOC_KEEPALIVE:
200		gef_wdt_service();
201		wdt_status |= WDIOF_KEEPALIVEPING;
202		break;
203
204	case WDIOC_SETTIMEOUT:
205		if (get_user(timeout, (int __user *)argp))
206			return -EFAULT;
207		gef_wdt_set_timeout(timeout);
208		/* Fall through */
209
210	case WDIOC_GETTIMEOUT:
211		if (put_user(gef_wdt_timeout, (int __user *)argp))
212			return -EFAULT;
213		break;
214
215	default:
216		return -ENOTTY;
217	}
218
219	return 0;
220}
221
222static int gef_wdt_open(struct inode *inode, struct file *file)
223{
224	if (test_and_set_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags))
225		return -EBUSY;
226
227	if (nowayout)
228		__module_get(THIS_MODULE);
229
230	gef_wdt_handler_enable();
231
232	return nonseekable_open(inode, file);
233}
234
235static int gef_wdt_release(struct inode *inode, struct file *file)
236{
237	if (expect_close == 42)
238		gef_wdt_handler_disable();
239	else {
240		pr_crit("unexpected close, not stopping timer!\n");
241		gef_wdt_service();
242	}
243	expect_close = 0;
244
245	clear_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags);
246
247	return 0;
248}
249
250static const struct file_operations gef_wdt_fops = {
251	.owner = THIS_MODULE,
252	.llseek = no_llseek,
253	.write = gef_wdt_write,
254	.unlocked_ioctl = gef_wdt_ioctl,
255	.open = gef_wdt_open,
256	.release = gef_wdt_release,
257};
258
259static struct miscdevice gef_wdt_miscdev = {
260	.minor = WATCHDOG_MINOR,
261	.name = "watchdog",
262	.fops = &gef_wdt_fops,
263};
264
265
266static int gef_wdt_probe(struct platform_device *dev)
267{
268	int timeout = 10;
269	u32 freq;
270
271	bus_clk = 133; /* in MHz */
272
273	freq = fsl_get_sys_freq();
274	if (freq != -1)
275		bus_clk = freq;
276
277	/* Map devices registers into memory */
278	gef_wdt_regs = of_iomap(dev->dev.of_node, 0);
279	if (gef_wdt_regs == NULL)
280		return -ENOMEM;
281
282	gef_wdt_set_timeout(timeout);
283
284	gef_wdt_handler_disable();	/* in case timer was already running */
285
286	return misc_register(&gef_wdt_miscdev);
287}
288
289static int gef_wdt_remove(struct platform_device *dev)
290{
291	misc_deregister(&gef_wdt_miscdev);
292
293	gef_wdt_handler_disable();
294
295	iounmap(gef_wdt_regs);
296
297	return 0;
298}
299
300static const struct of_device_id gef_wdt_ids[] = {
301	{
302		.compatible = "gef,fpga-wdt",
303	},
304	{},
305};
306MODULE_DEVICE_TABLE(of, gef_wdt_ids);
307
308static struct platform_driver gef_wdt_driver = {
309	.driver = {
310		.name = "gef_wdt",
311		.of_match_table = gef_wdt_ids,
312	},
313	.probe		= gef_wdt_probe,
314	.remove		= gef_wdt_remove,
315};
316
317static int __init gef_wdt_init(void)
318{
319	pr_info("GE watchdog driver\n");
320	return platform_driver_register(&gef_wdt_driver);
321}
322
323static void __exit gef_wdt_exit(void)
324{
325	platform_driver_unregister(&gef_wdt_driver);
326}
327
328module_init(gef_wdt_init);
329module_exit(gef_wdt_exit);
330
331MODULE_AUTHOR("Martyn Welch <martyn.welch@ge.com>");
332MODULE_DESCRIPTION("GE watchdog driver");
333MODULE_LICENSE("GPL");
334MODULE_ALIAS("platform:gef_wdt");
335