1/*
2 * Copyright (c) 2014, NVIDIA CORPORATION.  All rights reserved.
3 *
4 * This program is free software; you can redistribute it and/or modify it
5 * under the terms and conditions of the GNU General Public License,
6 * version 2, as published by the Free Software Foundation.
7 *
8 * This program is distributed in the hope it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
11 * more details.
12 */
13
14#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/interrupt.h>
17#include <linux/io.h>
18#include <linux/of.h>
19#include <linux/platform_device.h>
20#include <linux/watchdog.h>
21
22/* minimum and maximum watchdog trigger timeout, in seconds */
23#define MIN_WDT_TIMEOUT			1
24#define MAX_WDT_TIMEOUT			255
25
26/*
27 * Base of the WDT registers, from the timer base address.  There are
28 * actually 5 watchdogs that can be configured (by pairing with an available
29 * timer), at bases 0x100 + (WDT ID) * 0x20, where WDT ID is 0 through 4.
30 * This driver only configures the first watchdog (WDT ID 0).
31 */
32#define WDT_BASE			0x100
33#define WDT_ID				0
34
35/*
36 * Register base of the timer that's selected for pairing with the watchdog.
37 * This driver arbitrarily uses timer 5, which is currently unused by
38 * other drivers (in particular, the Tegra clocksource driver).  If this
39 * needs to change, take care that the new timer is not used by the
40 * clocksource driver.
41 */
42#define WDT_TIMER_BASE			0x60
43#define WDT_TIMER_ID			5
44
45/* WDT registers */
46#define WDT_CFG				0x0
47#define WDT_CFG_PERIOD_SHIFT		4
48#define WDT_CFG_PERIOD_MASK		0xff
49#define WDT_CFG_INT_EN			(1 << 12)
50#define WDT_CFG_PMC2CAR_RST_EN		(1 << 15)
51#define WDT_STS				0x4
52#define WDT_STS_COUNT_SHIFT		4
53#define WDT_STS_COUNT_MASK		0xff
54#define WDT_STS_EXP_SHIFT		12
55#define WDT_STS_EXP_MASK		0x3
56#define WDT_CMD				0x8
57#define WDT_CMD_START_COUNTER		(1 << 0)
58#define WDT_CMD_DISABLE_COUNTER		(1 << 1)
59#define WDT_UNLOCK			(0xc)
60#define WDT_UNLOCK_PATTERN		(0xc45a << 0)
61
62/* Timer registers */
63#define TIMER_PTV			0x0
64#define TIMER_EN			(1 << 31)
65#define TIMER_PERIODIC			(1 << 30)
66
67struct tegra_wdt {
68	struct watchdog_device	wdd;
69	void __iomem		*wdt_regs;
70	void __iomem		*tmr_regs;
71};
72
73#define WDT_HEARTBEAT 120
74static int heartbeat = WDT_HEARTBEAT;
75module_param(heartbeat, int, 0);
76MODULE_PARM_DESC(heartbeat,
77	"Watchdog heartbeats in seconds. (default = "
78	__MODULE_STRING(WDT_HEARTBEAT) ")");
79
80static bool nowayout = WATCHDOG_NOWAYOUT;
81module_param(nowayout, bool, 0);
82MODULE_PARM_DESC(nowayout,
83	"Watchdog cannot be stopped once started (default="
84	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
85
86static int tegra_wdt_start(struct watchdog_device *wdd)
87{
88	struct tegra_wdt *wdt = watchdog_get_drvdata(wdd);
89	u32 val;
90
91	/*
92	 * This thing has a fixed 1MHz clock.  Normally, we would set the
93	 * period to 1 second by writing 1000000ul, but the watchdog system
94	 * reset actually occurs on the 4th expiration of this counter,
95	 * so we set the period to 1/4 of this amount.
96	 */
97	val = 1000000ul / 4;
98	val |= (TIMER_EN | TIMER_PERIODIC);
99	writel(val, wdt->tmr_regs + TIMER_PTV);
100
101	/*
102	 * Set number of periods and start counter.
103	 *
104	 * Interrupt handler is not required for user space
105	 * WDT accesses, since the caller is responsible to ping the
106	 * WDT to reset the counter before expiration, through ioctls.
107	 */
108	val = WDT_TIMER_ID |
109	      (wdd->timeout << WDT_CFG_PERIOD_SHIFT) |
110	      WDT_CFG_PMC2CAR_RST_EN;
111	writel(val, wdt->wdt_regs + WDT_CFG);
112
113	writel(WDT_CMD_START_COUNTER, wdt->wdt_regs + WDT_CMD);
114
115	return 0;
116}
117
118static int tegra_wdt_stop(struct watchdog_device *wdd)
119{
120	struct tegra_wdt *wdt = watchdog_get_drvdata(wdd);
121
122	writel(WDT_UNLOCK_PATTERN, wdt->wdt_regs + WDT_UNLOCK);
123	writel(WDT_CMD_DISABLE_COUNTER, wdt->wdt_regs + WDT_CMD);
124	writel(0, wdt->tmr_regs + TIMER_PTV);
125
126	return 0;
127}
128
129static int tegra_wdt_ping(struct watchdog_device *wdd)
130{
131	struct tegra_wdt *wdt = watchdog_get_drvdata(wdd);
132
133	writel(WDT_CMD_START_COUNTER, wdt->wdt_regs + WDT_CMD);
134
135	return 0;
136}
137
138static int tegra_wdt_set_timeout(struct watchdog_device *wdd,
139				 unsigned int timeout)
140{
141	wdd->timeout = timeout;
142
143	if (watchdog_active(wdd))
144		return tegra_wdt_start(wdd);
145
146	return 0;
147}
148
149static unsigned int tegra_wdt_get_timeleft(struct watchdog_device *wdd)
150{
151	struct tegra_wdt *wdt = watchdog_get_drvdata(wdd);
152	u32 val;
153	int count;
154	int exp;
155
156	val = readl(wdt->wdt_regs + WDT_STS);
157
158	/* Current countdown (from timeout) */
159	count = (val >> WDT_STS_COUNT_SHIFT) & WDT_STS_COUNT_MASK;
160
161	/* Number of expirations (we are waiting for the 4th expiration) */
162	exp = (val >> WDT_STS_EXP_SHIFT) & WDT_STS_EXP_MASK;
163
164	/*
165	 * The entire thing is divided by 4 because we are ticking down 4 times
166	 * faster due to needing to wait for the 4th expiration.
167	 */
168	return (((3 - exp) * wdd->timeout) + count) / 4;
169}
170
171static const struct watchdog_info tegra_wdt_info = {
172	.options	= WDIOF_SETTIMEOUT |
173			  WDIOF_MAGICCLOSE |
174			  WDIOF_KEEPALIVEPING,
175	.firmware_version = 0,
176	.identity	= "Tegra Watchdog",
177};
178
179static struct watchdog_ops tegra_wdt_ops = {
180	.owner = THIS_MODULE,
181	.start = tegra_wdt_start,
182	.stop = tegra_wdt_stop,
183	.ping = tegra_wdt_ping,
184	.set_timeout = tegra_wdt_set_timeout,
185	.get_timeleft = tegra_wdt_get_timeleft,
186};
187
188static int tegra_wdt_probe(struct platform_device *pdev)
189{
190	struct watchdog_device *wdd;
191	struct tegra_wdt *wdt;
192	struct resource *res;
193	void __iomem *regs;
194	int ret;
195
196	/* This is the timer base. */
197	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
198	regs = devm_ioremap_resource(&pdev->dev, res);
199	if (IS_ERR(regs))
200		return PTR_ERR(regs);
201
202	/*
203	 * Allocate our watchdog driver data, which has the
204	 * struct watchdog_device nested within it.
205	 */
206	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
207	if (!wdt)
208		return -ENOMEM;
209
210	/* Initialize struct tegra_wdt. */
211	wdt->wdt_regs = regs + WDT_BASE;
212	wdt->tmr_regs = regs + WDT_TIMER_BASE;
213
214	/* Initialize struct watchdog_device. */
215	wdd = &wdt->wdd;
216	wdd->timeout = heartbeat;
217	wdd->info = &tegra_wdt_info;
218	wdd->ops = &tegra_wdt_ops;
219	wdd->min_timeout = MIN_WDT_TIMEOUT;
220	wdd->max_timeout = MAX_WDT_TIMEOUT;
221
222	watchdog_set_drvdata(wdd, wdt);
223
224	watchdog_set_nowayout(wdd, nowayout);
225
226	ret = watchdog_register_device(wdd);
227	if (ret) {
228		dev_err(&pdev->dev,
229			"failed to register watchdog device\n");
230		return ret;
231	}
232
233	platform_set_drvdata(pdev, wdt);
234
235	dev_info(&pdev->dev,
236		 "initialized (heartbeat = %d sec, nowayout = %d)\n",
237		 heartbeat, nowayout);
238
239	return 0;
240}
241
242static int tegra_wdt_remove(struct platform_device *pdev)
243{
244	struct tegra_wdt *wdt = platform_get_drvdata(pdev);
245
246	tegra_wdt_stop(&wdt->wdd);
247
248	watchdog_unregister_device(&wdt->wdd);
249
250	dev_info(&pdev->dev, "removed wdt\n");
251
252	return 0;
253}
254
255#ifdef CONFIG_PM_SLEEP
256static int tegra_wdt_runtime_suspend(struct device *dev)
257{
258	struct tegra_wdt *wdt = dev_get_drvdata(dev);
259
260	if (watchdog_active(&wdt->wdd))
261		tegra_wdt_stop(&wdt->wdd);
262
263	return 0;
264}
265
266static int tegra_wdt_runtime_resume(struct device *dev)
267{
268	struct tegra_wdt *wdt = dev_get_drvdata(dev);
269
270	if (watchdog_active(&wdt->wdd))
271		tegra_wdt_start(&wdt->wdd);
272
273	return 0;
274}
275#endif
276
277static const struct of_device_id tegra_wdt_of_match[] = {
278	{ .compatible = "nvidia,tegra30-timer", },
279	{ },
280};
281MODULE_DEVICE_TABLE(of, tegra_wdt_of_match);
282
283static const struct dev_pm_ops tegra_wdt_pm_ops = {
284	SET_SYSTEM_SLEEP_PM_OPS(tegra_wdt_runtime_suspend,
285				tegra_wdt_runtime_resume)
286};
287
288static struct platform_driver tegra_wdt_driver = {
289	.probe		= tegra_wdt_probe,
290	.remove		= tegra_wdt_remove,
291	.driver		= {
292		.name	= "tegra-wdt",
293		.pm	= &tegra_wdt_pm_ops,
294		.of_match_table = tegra_wdt_of_match,
295	},
296};
297module_platform_driver(tegra_wdt_driver);
298
299MODULE_AUTHOR("NVIDIA Corporation");
300MODULE_DESCRIPTION("Tegra Watchdog Driver");
301MODULE_LICENSE("GPL v2");
302