1/*
2 * LTC2952 (PowerPath) driver
3 *
4 * Copyright (C) 2014, Xsens Technologies BV <info@xsens.com>
5 * Maintainer: Ren� Moll <linux@r-moll.nl>
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; either version 2
10 * of the License, or (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15 * GNU General Public License for more details.
16 *
17 * ----------------------------------------
18 * - Description
19 * ----------------------------------------
20 *
21 * This driver is to be used with an external PowerPath Controller (LTC2952).
22 * Its function is to determine when a external shut down is triggered
23 * and react by properly shutting down the system.
24 *
25 * This driver expects a device tree with a ltc2952 entry for pin mapping.
26 *
27 * ----------------------------------------
28 * - GPIO
29 * ----------------------------------------
30 *
31 * The following GPIOs are used:
32 * - trigger (input)
33 *     A level change indicates the shut-down trigger. If it's state reverts
34 *     within the time-out defined by trigger_delay, the shut down is not
35 *     executed. If no pin is assigned to this input, the driver will start the
36 *     watchdog toggle immediately. The chip will only power off the system if
37 *     it is requested to do so through the kill line.
38 *
39 * - watchdog (output)
40 *     Once a shut down is triggered, the driver will toggle this signal,
41 *     with an internal (wde_interval) to stall the hardware shut down.
42 *
43 * - kill (output)
44 *     The last action during shut down is triggering this signalling, such
45 *     that the PowerPath Control will power down the hardware.
46 *
47 * ----------------------------------------
48 * - Interrupts
49 * ----------------------------------------
50 *
51 * The driver requires a non-shared, edge-triggered interrupt on the trigger
52 * GPIO.
53 *
54 */
55
56#include <linux/kernel.h>
57#include <linux/init.h>
58#include <linux/interrupt.h>
59#include <linux/device.h>
60#include <linux/platform_device.h>
61#include <linux/ktime.h>
62#include <linux/slab.h>
63#include <linux/kmod.h>
64#include <linux/module.h>
65#include <linux/gpio/consumer.h>
66#include <linux/reboot.h>
67
68struct ltc2952_poweroff {
69	struct hrtimer timer_trigger;
70	struct hrtimer timer_wde;
71
72	ktime_t trigger_delay;
73	ktime_t wde_interval;
74
75	struct device *dev;
76
77	struct gpio_desc *gpio_trigger;
78	struct gpio_desc *gpio_watchdog;
79	struct gpio_desc *gpio_kill;
80
81	bool kernel_panic;
82	struct notifier_block panic_notifier;
83};
84
85#define to_ltc2952(p, m) container_of(p, struct ltc2952_poweroff, m)
86
87/*
88 * This global variable is only needed for pm_power_off. We should
89 * remove it entirely once we don't need the global state anymore.
90 */
91static struct ltc2952_poweroff *ltc2952_data;
92
93/**
94 * ltc2952_poweroff_timer_wde - Timer callback
95 * Toggles the watchdog reset signal each wde_interval
96 *
97 * @timer: corresponding timer
98 *
99 * Returns HRTIMER_RESTART for an infinite loop which will only stop when the
100 * machine actually shuts down
101 */
102static enum hrtimer_restart ltc2952_poweroff_timer_wde(struct hrtimer *timer)
103{
104	ktime_t now;
105	int state;
106	unsigned long overruns;
107	struct ltc2952_poweroff *data = to_ltc2952(timer, timer_wde);
108
109	if (data->kernel_panic)
110		return HRTIMER_NORESTART;
111
112	state = gpiod_get_value(data->gpio_watchdog);
113	gpiod_set_value(data->gpio_watchdog, !state);
114
115	now = hrtimer_cb_get_time(timer);
116	overruns = hrtimer_forward(timer, now, data->wde_interval);
117
118	return HRTIMER_RESTART;
119}
120
121static void ltc2952_poweroff_start_wde(struct ltc2952_poweroff *data)
122{
123	hrtimer_start(&data->timer_wde, data->wde_interval, HRTIMER_MODE_REL);
124}
125
126static enum hrtimer_restart
127ltc2952_poweroff_timer_trigger(struct hrtimer *timer)
128{
129	struct ltc2952_poweroff *data = to_ltc2952(timer, timer_trigger);
130
131	ltc2952_poweroff_start_wde(data);
132	dev_info(data->dev, "executing shutdown\n");
133	orderly_poweroff(true);
134
135	return HRTIMER_NORESTART;
136}
137
138/**
139 * ltc2952_poweroff_handler - Interrupt handler
140 * Triggered each time the trigger signal changes state and (de)activates a
141 * time-out (timer_trigger). Once the time-out is actually reached the shut
142 * down is executed.
143 *
144 * @irq: IRQ number
145 * @dev_id: pointer to the main data structure
146 */
147static irqreturn_t ltc2952_poweroff_handler(int irq, void *dev_id)
148{
149	struct ltc2952_poweroff *data = dev_id;
150
151	if (data->kernel_panic || hrtimer_active(&data->timer_wde)) {
152		/* shutdown is already triggered, nothing to do any more */
153		return IRQ_HANDLED;
154	}
155
156	if (gpiod_get_value(data->gpio_trigger)) {
157		hrtimer_start(&data->timer_trigger, data->trigger_delay,
158			      HRTIMER_MODE_REL);
159	} else {
160		hrtimer_cancel(&data->timer_trigger);
161	}
162	return IRQ_HANDLED;
163}
164
165static void ltc2952_poweroff_kill(void)
166{
167	gpiod_set_value(ltc2952_data->gpio_kill, 1);
168}
169
170static void ltc2952_poweroff_default(struct ltc2952_poweroff *data)
171{
172	data->wde_interval = ktime_set(0, 300L*1E6L);
173	data->trigger_delay = ktime_set(2, 500L*1E6L);
174
175	hrtimer_init(&data->timer_trigger, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
176	data->timer_trigger.function = ltc2952_poweroff_timer_trigger;
177
178	hrtimer_init(&data->timer_wde, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
179	data->timer_wde.function = ltc2952_poweroff_timer_wde;
180}
181
182static int ltc2952_poweroff_init(struct platform_device *pdev)
183{
184	int ret;
185	struct ltc2952_poweroff *data = platform_get_drvdata(pdev);
186
187	ltc2952_poweroff_default(data);
188
189	data->gpio_watchdog = devm_gpiod_get(&pdev->dev, "watchdog",
190					     GPIOD_OUT_LOW);
191	if (IS_ERR(data->gpio_watchdog)) {
192		ret = PTR_ERR(data->gpio_watchdog);
193		dev_err(&pdev->dev, "unable to claim gpio \"watchdog\"\n");
194		return ret;
195	}
196
197	data->gpio_kill = devm_gpiod_get(&pdev->dev, "kill", GPIOD_OUT_LOW);
198	if (IS_ERR(data->gpio_kill)) {
199		ret = PTR_ERR(data->gpio_kill);
200		dev_err(&pdev->dev, "unable to claim gpio \"kill\"\n");
201		return ret;
202	}
203
204	data->gpio_trigger = devm_gpiod_get_optional(&pdev->dev, "trigger",
205						     GPIOD_IN);
206	if (IS_ERR(data->gpio_trigger)) {
207		/*
208		 * It's not a problem if the trigger gpio isn't available, but
209		 * it is worth a warning if its use was defined in the device
210		 * tree.
211		 */
212		dev_err(&pdev->dev, "unable to claim gpio \"trigger\"\n");
213		data->gpio_trigger = NULL;
214	}
215
216	if (devm_request_irq(&pdev->dev, gpiod_to_irq(data->gpio_trigger),
217			     ltc2952_poweroff_handler,
218			     (IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING),
219			     "ltc2952-poweroff",
220			     data)) {
221		/*
222		 * Some things may have happened:
223		 * - No trigger input was defined
224		 * - Claiming the GPIO failed
225		 * - We could not map to an IRQ
226		 * - We couldn't register an interrupt handler
227		 *
228		 * None of these really are problems, but all of them
229		 * disqualify the push button from controlling the power.
230		 *
231		 * It is therefore important to note that if the ltc2952
232		 * detects a button press for long enough, it will still start
233		 * its own powerdown window and cut the power on us if we don't
234		 * start the watchdog trigger.
235		 */
236		if (data->gpio_trigger) {
237			dev_warn(&pdev->dev,
238				 "unable to configure the trigger interrupt\n");
239			devm_gpiod_put(&pdev->dev, data->gpio_trigger);
240			data->gpio_trigger = NULL;
241		}
242		dev_info(&pdev->dev,
243			 "power down trigger input will not be used\n");
244		ltc2952_poweroff_start_wde(data);
245	}
246
247	return 0;
248}
249
250static int ltc2952_poweroff_notify_panic(struct notifier_block *nb,
251					 unsigned long code, void *unused)
252{
253	struct ltc2952_poweroff *data = to_ltc2952(nb, panic_notifier);
254
255	data->kernel_panic = true;
256	return NOTIFY_DONE;
257}
258
259static int ltc2952_poweroff_probe(struct platform_device *pdev)
260{
261	int ret;
262	struct ltc2952_poweroff *data;
263
264	if (pm_power_off) {
265		dev_err(&pdev->dev, "pm_power_off already registered");
266		return -EBUSY;
267	}
268
269	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
270	if (!data)
271		return -ENOMEM;
272
273	data->dev = &pdev->dev;
274	platform_set_drvdata(pdev, data);
275
276	ret = ltc2952_poweroff_init(pdev);
277	if (ret)
278		return ret;
279
280	/* TODO: remove ltc2952_data */
281	ltc2952_data = data;
282	pm_power_off = ltc2952_poweroff_kill;
283
284	data->panic_notifier.notifier_call = ltc2952_poweroff_notify_panic;
285	atomic_notifier_chain_register(&panic_notifier_list,
286				       &data->panic_notifier);
287	dev_info(&pdev->dev, "probe successful\n");
288
289	return 0;
290}
291
292static int ltc2952_poweroff_remove(struct platform_device *pdev)
293{
294	struct ltc2952_poweroff *data = platform_get_drvdata(pdev);
295
296	pm_power_off = NULL;
297	hrtimer_cancel(&data->timer_trigger);
298	hrtimer_cancel(&data->timer_wde);
299	atomic_notifier_chain_unregister(&panic_notifier_list,
300					 &data->panic_notifier);
301	return 0;
302}
303
304static const struct of_device_id of_ltc2952_poweroff_match[] = {
305	{ .compatible = "lltc,ltc2952"},
306	{},
307};
308MODULE_DEVICE_TABLE(of, of_ltc2952_poweroff_match);
309
310static struct platform_driver ltc2952_poweroff_driver = {
311	.probe = ltc2952_poweroff_probe,
312	.remove = ltc2952_poweroff_remove,
313	.driver = {
314		.name = "ltc2952-poweroff",
315		.of_match_table = of_ltc2952_poweroff_match,
316	},
317};
318
319module_platform_driver(ltc2952_poweroff_driver);
320
321MODULE_AUTHOR("Ren� Moll <rene.moll@xsens.com>");
322MODULE_DESCRIPTION("LTC PowerPath power-off driver");
323MODULE_LICENSE("GPL v2");
324