1/*
  2 * Watchdog driver for TS-4800 based boards
  3 *
  4 * Copyright (c) 2015 - Savoir-faire Linux
  5 *
  6 * This file is licensed under the terms of the GNU General Public
  7 * License version 2. This program is licensed "as is" without any
  8 * warranty of any kind, whether express or implied.
  9 */
 10
 11#include <linux/kernel.h>
 12#include <linux/mfd/syscon.h>
 13#include <linux/module.h>
 14#include <linux/of.h>
 15#include <linux/platform_device.h>
 16#include <linux/regmap.h>
 17#include <linux/watchdog.h>
 18
 19static bool nowayout = WATCHDOG_NOWAYOUT;
 20module_param(nowayout, bool, 0);
 21MODULE_PARM_DESC(nowayout,
 22	"Watchdog cannot be stopped once started (default="
 23	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
 24
 25/* possible feed values */
 26#define TS4800_WDT_FEED_2S       0x1
 27#define TS4800_WDT_FEED_10S      0x2
 28#define TS4800_WDT_DISABLE       0x3
 29
 30struct ts4800_wdt {
 31	struct watchdog_device  wdd;
 32	struct regmap           *regmap;
 33	u32                     feed_offset;
 34	u32                     feed_val;
 35};
 36
 37/*
 38 * TS-4800 supports the following timeout values:
 39 *
 40 *   value desc
 41 *   ---------------------
 42 *     0    feed for 338ms
 43 *     1    feed for 2.706s
 44 *     2    feed for 10.824s
 45 *     3    disable watchdog
 46 *
 47 * Keep the regmap/timeout map ordered by timeout
 48 */
 49static const struct {
 50	const int timeout;
 51	const int regval;
 52} ts4800_wdt_map[] = {
 53	{ 2,  TS4800_WDT_FEED_2S },
 54	{ 10, TS4800_WDT_FEED_10S },
 55};
 56
 57#define MAX_TIMEOUT_INDEX       (ARRAY_SIZE(ts4800_wdt_map) - 1)
 58
 59static void ts4800_write_feed(struct ts4800_wdt *wdt, u32 val)
 60{
 61	regmap_write(wdt->regmap, wdt->feed_offset, val);
 62}
 63
 64static int ts4800_wdt_start(struct watchdog_device *wdd)
 65{
 66	struct ts4800_wdt *wdt = watchdog_get_drvdata(wdd);
 67
 68	ts4800_write_feed(wdt, wdt->feed_val);
 69	return 0;
 70}
 71
 72static int ts4800_wdt_stop(struct watchdog_device *wdd)
 73{
 74	struct ts4800_wdt *wdt = watchdog_get_drvdata(wdd);
 75
 76	ts4800_write_feed(wdt, TS4800_WDT_DISABLE);
 77	return 0;
 78}
 79
 80static int ts4800_wdt_set_timeout(struct watchdog_device *wdd,
 81				  unsigned int timeout)
 82{
 83	struct ts4800_wdt *wdt = watchdog_get_drvdata(wdd);
 84	int i;
 85
 86	for (i = 0; i < MAX_TIMEOUT_INDEX; i++) {
 87		if (ts4800_wdt_map[i].timeout >= timeout)
 88			break;
 89	}
 90
 91	wdd->timeout = ts4800_wdt_map[i].timeout;
 92	wdt->feed_val = ts4800_wdt_map[i].regval;
 93
 94	return 0;
 95}
 96
 97static const struct watchdog_ops ts4800_wdt_ops = {
 98	.owner = THIS_MODULE,
 99	.start = ts4800_wdt_start,
100	.stop = ts4800_wdt_stop,
101	.set_timeout = ts4800_wdt_set_timeout,
102};
103
104static const struct watchdog_info ts4800_wdt_info = {
105	.options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
106	.identity = "TS-4800 Watchdog",
107};
108
109static int ts4800_wdt_probe(struct platform_device *pdev)
110{
111	struct device_node *np = pdev->dev.of_node;
112	struct device_node *syscon_np;
113	struct watchdog_device *wdd;
114	struct ts4800_wdt *wdt;
115	u32 reg;
116	int ret;
117
118	syscon_np = of_parse_phandle(np, "syscon", 0);
119	if (!syscon_np) {
120		dev_err(&pdev->dev, "no syscon property\n");
121		return -ENODEV;
122	}
123
124	ret = of_property_read_u32_index(np, "syscon", 1, &reg);
125	if (ret < 0) {
126		dev_err(&pdev->dev, "no offset in syscon\n");
127		return ret;
128	}
129
130	/* allocate memory for watchdog struct */
131	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
132	if (!wdt)
133		return -ENOMEM;
134
135	/* set regmap and offset to know where to write */
136	wdt->feed_offset = reg;
137	wdt->regmap = syscon_node_to_regmap(syscon_np);
138	if (IS_ERR(wdt->regmap)) {
139		dev_err(&pdev->dev, "cannot get parent's regmap\n");
140		return PTR_ERR(wdt->regmap);
141	}
142
143	/* Initialize struct watchdog_device */
144	wdd = &wdt->wdd;
145	wdd->parent = &pdev->dev;
146	wdd->info = &ts4800_wdt_info;
147	wdd->ops = &ts4800_wdt_ops;
148	wdd->min_timeout = ts4800_wdt_map[0].timeout;
149	wdd->max_timeout = ts4800_wdt_map[MAX_TIMEOUT_INDEX].timeout;
150
151	watchdog_set_drvdata(wdd, wdt);
152	watchdog_set_nowayout(wdd, nowayout);
153	watchdog_init_timeout(wdd, 0, &pdev->dev);
154
155	/*
156	 * As this watchdog supports only a few values, ts4800_wdt_set_timeout
157	 * must be called to initialize timeout and feed_val with valid values.
158	 * Default to maximum timeout if none, or an invalid one, is provided in
159	 * device tree.
160	 */
161	if (!wdd->timeout)
162		wdd->timeout = wdd->max_timeout;
163	ts4800_wdt_set_timeout(wdd, wdd->timeout);
164
165	/*
166	 * The feed register is write-only, so it is not possible to determine
167	 * watchdog's state. Disable it to be in a known state.
168	 */
169	ts4800_wdt_stop(wdd);
170
171	ret = watchdog_register_device(wdd);
172	if (ret) {
173		dev_err(&pdev->dev,
174			"failed to register watchdog device\n");
175		return ret;
176	}
177
178	platform_set_drvdata(pdev, wdt);
179
180	dev_info(&pdev->dev,
181		 "initialized (timeout = %d sec, nowayout = %d)\n",
182		 wdd->timeout, nowayout);
183
184	return 0;
185}
186
187static int ts4800_wdt_remove(struct platform_device *pdev)
188{
189	struct ts4800_wdt *wdt = platform_get_drvdata(pdev);
190
191	watchdog_unregister_device(&wdt->wdd);
192
193	return 0;
194}
195
196static const struct of_device_id ts4800_wdt_of_match[] = {
197	{ .compatible = "technologic,ts4800-wdt", },
198	{ },
199};
200MODULE_DEVICE_TABLE(of, ts4800_wdt_of_match);
201
202static struct platform_driver ts4800_wdt_driver = {
203	.probe		= ts4800_wdt_probe,
204	.remove		= ts4800_wdt_remove,
205	.driver		= {
206		.name	= "ts4800_wdt",
207		.of_match_table = ts4800_wdt_of_match,
208	},
209};
210
211module_platform_driver(ts4800_wdt_driver);
212
213MODULE_AUTHOR("Damien Riegel <damien.riegel@savoirfairelinux.com>");
214MODULE_LICENSE("GPL v2");
215MODULE_ALIAS("platform:ts4800_wdt");