1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * GE watchdog userspace interface
4 *
5 * Author:  Martyn Welch <martyn.welch@ge.com>
6 *
7 * Copyright 2008 GE Intelligent Platforms Embedded Systems, Inc.
8 *
9 * Based on: mv64x60_wdt.c (MV64X60 watchdog userspace interface)
10 *   Author: James Chapman <jchapman@katalix.com>
11 */
12
13/* TODO:
14 * This driver does not provide support for the hardwares capability of sending
15 * an interrupt at a programmable threshold.
16 *
17 * This driver currently can only support 1 watchdog - there are 2 in the
18 * hardware that this driver supports. Thus one could be configured as a
19 * process-based watchdog (via /dev/watchdog), the second (using the interrupt
20 * capabilities) a kernel-based watchdog.
21 */
22
23#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
24
25#include <linux/kernel.h>
26#include <linux/compiler.h>
27#include <linux/init.h>
28#include <linux/module.h>
29#include <linux/miscdevice.h>
30#include <linux/watchdog.h>
31#include <linux/fs.h>
32#include <linux/of.h>
33#include <linux/of_address.h>
34#include <linux/platform_device.h>
35#include <linux/io.h>
36#include <linux/uaccess.h>
37
38#include <sysdev/fsl_soc.h>
39
40/*
41 * The watchdog configuration register contains a pair of 2-bit fields,
42 *   1.  a reload field, bits 27-26, which triggers a reload of
43 *       the countdown register, and
44 *   2.  an enable field, bits 25-24, which toggles between
45 *       enabling and disabling the watchdog timer.
46 * Bit 31 is a read-only field which indicates whether the
47 * watchdog timer is currently enabled.
48 *
49 * The low 24 bits contain the timer reload value.
50 */
51#define GEF_WDC_ENABLE_SHIFT	24
52#define GEF_WDC_SERVICE_SHIFT	26
53#define GEF_WDC_ENABLED_SHIFT	31
54
55#define GEF_WDC_ENABLED_TRUE	1
56#define GEF_WDC_ENABLED_FALSE	0
57
58/* Flags bits */
59#define GEF_WDOG_FLAG_OPENED	0
60
61static unsigned long wdt_flags;
62static int wdt_status;
63static void __iomem *gef_wdt_regs;
64static int gef_wdt_timeout;
65static int gef_wdt_count;
66static unsigned int bus_clk;
67static char expect_close;
68static DEFINE_SPINLOCK(gef_wdt_spinlock);
69
70static bool nowayout = WATCHDOG_NOWAYOUT;
71module_param(nowayout, bool, 0);
72MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
73	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
74
75
76static int gef_wdt_toggle_wdc(int enabled_predicate, int field_shift)
77{
78	u32 data;
79	u32 enabled;
80	int ret = 0;
81
82	spin_lock(&gef_wdt_spinlock);
83	data = ioread32be(gef_wdt_regs);
84	enabled = (data >> GEF_WDC_ENABLED_SHIFT) & 1;
85
86	/* only toggle the requested field if enabled state matches predicate */
87	if ((enabled ^ enabled_predicate) == 0) {
88		/* We write a 1, then a 2 -- to the appropriate field */
89		data = (1 << field_shift) | gef_wdt_count;
90		iowrite32be(data, gef_wdt_regs);
91
92		data = (2 << field_shift) | gef_wdt_count;
93		iowrite32be(data, gef_wdt_regs);
94		ret = 1;
95	}
96	spin_unlock(&gef_wdt_spinlock);
97
98	return ret;
99}
100
101static void gef_wdt_service(void)
102{
103	gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
104		GEF_WDC_SERVICE_SHIFT);
105}
106
107static void gef_wdt_handler_enable(void)
108{
109	if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_FALSE,
110				   GEF_WDC_ENABLE_SHIFT)) {
111		gef_wdt_service();
112		pr_notice("watchdog activated\n");
113	}
114}
115
116static void gef_wdt_handler_disable(void)
117{
118	if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
119				   GEF_WDC_ENABLE_SHIFT))
120		pr_notice("watchdog deactivated\n");
121}
122
123static void gef_wdt_set_timeout(unsigned int timeout)
124{
125	/* maximum bus cycle count is 0xFFFFFFFF */
126	if (timeout > 0xFFFFFFFF / bus_clk)
127		timeout = 0xFFFFFFFF / bus_clk;
128
129	/* Register only holds upper 24 bits, bit shifted into lower 24 */
130	gef_wdt_count = (timeout * bus_clk) >> 8;
131	gef_wdt_timeout = timeout;
132}
133
134
135static ssize_t gef_wdt_write(struct file *file, const char __user *data,
136				 size_t len, loff_t *ppos)
137{
138	if (len) {
139		if (!nowayout) {
140			size_t i;
141
142			expect_close = 0;
143
144			for (i = 0; i != len; i++) {
145				char c;
146				if (get_user(c, data + i))
147					return -EFAULT;
148				if (c == 'V')
149					expect_close = 42;
150			}
151		}
152		gef_wdt_service();
153	}
154
155	return len;
156}
157
158static long gef_wdt_ioctl(struct file *file, unsigned int cmd,
159							unsigned long arg)
160{
161	int timeout;
162	int options;
163	void __user *argp = (void __user *)arg;
164	static const struct watchdog_info info = {
165		.options =	WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
166				WDIOF_KEEPALIVEPING,
167		.firmware_version = 0,
168		.identity = "GE watchdog",
169	};
170
171	switch (cmd) {
172	case WDIOC_GETSUPPORT:
173		if (copy_to_user(argp, &info, sizeof(info)))
174			return -EFAULT;
175		break;
176
177	case WDIOC_GETSTATUS:
178	case WDIOC_GETBOOTSTATUS:
179		if (put_user(wdt_status, (int __user *)argp))
180			return -EFAULT;
181		wdt_status &= ~WDIOF_KEEPALIVEPING;
182		break;
183
184	case WDIOC_SETOPTIONS:
185		if (get_user(options, (int __user *)argp))
186			return -EFAULT;
187
188		if (options & WDIOS_DISABLECARD)
189			gef_wdt_handler_disable();
190
191		if (options & WDIOS_ENABLECARD)
192			gef_wdt_handler_enable();
193		break;
194
195	case WDIOC_KEEPALIVE:
196		gef_wdt_service();
197		wdt_status |= WDIOF_KEEPALIVEPING;
198		break;
199
200	case WDIOC_SETTIMEOUT:
201		if (get_user(timeout, (int __user *)argp))
202			return -EFAULT;
203		gef_wdt_set_timeout(timeout);
204		fallthrough;
205
206	case WDIOC_GETTIMEOUT:
207		if (put_user(gef_wdt_timeout, (int __user *)argp))
208			return -EFAULT;
209		break;
210
211	default:
212		return -ENOTTY;
213	}
214
215	return 0;
216}
217
218static int gef_wdt_open(struct inode *inode, struct file *file)
219{
220	if (test_and_set_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags))
221		return -EBUSY;
222
223	if (nowayout)
224		__module_get(THIS_MODULE);
225
226	gef_wdt_handler_enable();
227
228	return stream_open(inode, file);
229}
230
231static int gef_wdt_release(struct inode *inode, struct file *file)
232{
233	if (expect_close == 42)
234		gef_wdt_handler_disable();
235	else {
236		pr_crit("unexpected close, not stopping timer!\n");
237		gef_wdt_service();
238	}
239	expect_close = 0;
240
241	clear_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags);
242
243	return 0;
244}
245
246static const struct file_operations gef_wdt_fops = {
247	.owner = THIS_MODULE,
248	.llseek = no_llseek,
249	.write = gef_wdt_write,
250	.unlocked_ioctl = gef_wdt_ioctl,
251	.compat_ioctl	= compat_ptr_ioctl,
252	.open = gef_wdt_open,
253	.release = gef_wdt_release,
254};
255
256static struct miscdevice gef_wdt_miscdev = {
257	.minor = WATCHDOG_MINOR,
258	.name = "watchdog",
259	.fops = &gef_wdt_fops,
260};
261
262
263static int gef_wdt_probe(struct platform_device *dev)
264{
265	int timeout = 10;
266	u32 freq;
267
268	bus_clk = 133; /* in MHz */
269
270	freq = fsl_get_sys_freq();
271	if (freq != -1)
272		bus_clk = freq;
273
274	/* Map devices registers into memory */
275	gef_wdt_regs = of_iomap(dev->dev.of_node, 0);
276	if (gef_wdt_regs == NULL)
277		return -ENOMEM;
278
279	gef_wdt_set_timeout(timeout);
280
281	gef_wdt_handler_disable();	/* in case timer was already running */
282
283	return misc_register(&gef_wdt_miscdev);
284}
285
286static void gef_wdt_remove(struct platform_device *dev)
287{
288	misc_deregister(&gef_wdt_miscdev);
289
290	gef_wdt_handler_disable();
291
292	iounmap(gef_wdt_regs);
293}
294
295static const struct of_device_id gef_wdt_ids[] = {
296	{
297		.compatible = "gef,fpga-wdt",
298	},
299	{},
300};
301MODULE_DEVICE_TABLE(of, gef_wdt_ids);
302
303static struct platform_driver gef_wdt_driver = {
304	.driver = {
305		.name = "gef_wdt",
306		.of_match_table = gef_wdt_ids,
307	},
308	.probe		= gef_wdt_probe,
309	.remove_new	= gef_wdt_remove,
310};
311
312static int __init gef_wdt_init(void)
313{
314	pr_info("GE watchdog driver\n");
315	return platform_driver_register(&gef_wdt_driver);
316}
317
318static void __exit gef_wdt_exit(void)
319{
320	platform_driver_unregister(&gef_wdt_driver);
321}
322
323module_init(gef_wdt_init);
324module_exit(gef_wdt_exit);
325
326MODULE_AUTHOR("Martyn Welch <martyn.welch@ge.com>");
327MODULE_DESCRIPTION("GE watchdog driver");
328MODULE_LICENSE("GPL");
329MODULE_ALIAS("platform:gef_wdt");
330