1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * LTC2952 (PowerPath) driver
4 *
5 * Copyright (C) 2014, Xsens Technologies BV <info@xsens.com>
6 * Maintainer: René Moll <linux@r-moll.nl>
7 *
8 * ----------------------------------------
9 * - Description
10 * ----------------------------------------
11 *
12 * This driver is to be used with an external PowerPath Controller (LTC2952).
13 * Its function is to determine when a external shut down is triggered
14 * and react by properly shutting down the system.
15 *
16 * This driver expects a device tree with a ltc2952 entry for pin mapping.
17 *
18 * ----------------------------------------
19 * - GPIO
20 * ----------------------------------------
21 *
22 * The following GPIOs are used:
23 * - trigger (input)
24 *     A level change indicates the shut-down trigger. If it's state reverts
25 *     within the time-out defined by trigger_delay, the shut down is not
26 *     executed. If no pin is assigned to this input, the driver will start the
27 *     watchdog toggle immediately. The chip will only power off the system if
28 *     it is requested to do so through the kill line.
29 *
30 * - watchdog (output)
31 *     Once a shut down is triggered, the driver will toggle this signal,
32 *     with an internal (wde_interval) to stall the hardware shut down.
33 *
34 * - kill (output)
35 *     The last action during shut down is triggering this signalling, such
36 *     that the PowerPath Control will power down the hardware.
37 *
38 * ----------------------------------------
39 * - Interrupts
40 * ----------------------------------------
41 *
42 * The driver requires a non-shared, edge-triggered interrupt on the trigger
43 * GPIO.
44 */
45
46#include <linux/kernel.h>
47#include <linux/init.h>
48#include <linux/interrupt.h>
49#include <linux/device.h>
50#include <linux/platform_device.h>
51#include <linux/ktime.h>
52#include <linux/slab.h>
53#include <linux/kmod.h>
54#include <linux/module.h>
55#include <linux/mod_devicetable.h>
56#include <linux/gpio/consumer.h>
57#include <linux/reboot.h>
58
59struct ltc2952_poweroff {
60	struct hrtimer timer_trigger;
61	struct hrtimer timer_wde;
62
63	ktime_t trigger_delay;
64	ktime_t wde_interval;
65
66	struct device *dev;
67
68	struct gpio_desc *gpio_trigger;
69	struct gpio_desc *gpio_watchdog;
70	struct gpio_desc *gpio_kill;
71
72	bool kernel_panic;
73	struct notifier_block panic_notifier;
74};
75
76#define to_ltc2952(p, m) container_of(p, struct ltc2952_poweroff, m)
77
78/*
79 * This global variable is only needed for pm_power_off. We should
80 * remove it entirely once we don't need the global state anymore.
81 */
82static struct ltc2952_poweroff *ltc2952_data;
83
84/**
85 * ltc2952_poweroff_timer_wde - Timer callback
86 * Toggles the watchdog reset signal each wde_interval
87 *
88 * @timer: corresponding timer
89 *
90 * Returns HRTIMER_RESTART for an infinite loop which will only stop when the
91 * machine actually shuts down
92 */
93static enum hrtimer_restart ltc2952_poweroff_timer_wde(struct hrtimer *timer)
94{
95	ktime_t now;
96	int state;
97	struct ltc2952_poweroff *data = to_ltc2952(timer, timer_wde);
98
99	if (data->kernel_panic)
100		return HRTIMER_NORESTART;
101
102	state = gpiod_get_value(data->gpio_watchdog);
103	gpiod_set_value(data->gpio_watchdog, !state);
104
105	now = hrtimer_cb_get_time(timer);
106	hrtimer_forward(timer, now, data->wde_interval);
107
108	return HRTIMER_RESTART;
109}
110
111static void ltc2952_poweroff_start_wde(struct ltc2952_poweroff *data)
112{
113	hrtimer_start(&data->timer_wde, data->wde_interval, HRTIMER_MODE_REL);
114}
115
116static enum hrtimer_restart
117ltc2952_poweroff_timer_trigger(struct hrtimer *timer)
118{
119	struct ltc2952_poweroff *data = to_ltc2952(timer, timer_trigger);
120
121	ltc2952_poweroff_start_wde(data);
122	dev_info(data->dev, "executing shutdown\n");
123	orderly_poweroff(true);
124
125	return HRTIMER_NORESTART;
126}
127
128/**
129 * ltc2952_poweroff_handler - Interrupt handler
130 * Triggered each time the trigger signal changes state and (de)activates a
131 * time-out (timer_trigger). Once the time-out is actually reached the shut
132 * down is executed.
133 *
134 * @irq: IRQ number
135 * @dev_id: pointer to the main data structure
136 */
137static irqreturn_t ltc2952_poweroff_handler(int irq, void *dev_id)
138{
139	struct ltc2952_poweroff *data = dev_id;
140
141	if (data->kernel_panic || hrtimer_active(&data->timer_wde)) {
142		/* shutdown is already triggered, nothing to do any more */
143		return IRQ_HANDLED;
144	}
145
146	if (gpiod_get_value(data->gpio_trigger)) {
147		hrtimer_start(&data->timer_trigger, data->trigger_delay,
148			      HRTIMER_MODE_REL);
149	} else {
150		hrtimer_cancel(&data->timer_trigger);
151	}
152	return IRQ_HANDLED;
153}
154
155static void ltc2952_poweroff_kill(void)
156{
157	gpiod_set_value(ltc2952_data->gpio_kill, 1);
158}
159
160static void ltc2952_poweroff_default(struct ltc2952_poweroff *data)
161{
162	data->wde_interval = 300L * NSEC_PER_MSEC;
163	data->trigger_delay = ktime_set(2, 500L * NSEC_PER_MSEC);
164
165	hrtimer_init(&data->timer_trigger, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
166	data->timer_trigger.function = ltc2952_poweroff_timer_trigger;
167
168	hrtimer_init(&data->timer_wde, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
169	data->timer_wde.function = ltc2952_poweroff_timer_wde;
170}
171
172static int ltc2952_poweroff_init(struct platform_device *pdev)
173{
174	int ret;
175	struct ltc2952_poweroff *data = platform_get_drvdata(pdev);
176
177	ltc2952_poweroff_default(data);
178
179	data->gpio_watchdog = devm_gpiod_get(&pdev->dev, "watchdog",
180					     GPIOD_OUT_LOW);
181	if (IS_ERR(data->gpio_watchdog)) {
182		ret = PTR_ERR(data->gpio_watchdog);
183		dev_err(&pdev->dev, "unable to claim gpio \"watchdog\"\n");
184		return ret;
185	}
186
187	data->gpio_kill = devm_gpiod_get(&pdev->dev, "kill", GPIOD_OUT_LOW);
188	if (IS_ERR(data->gpio_kill)) {
189		ret = PTR_ERR(data->gpio_kill);
190		dev_err(&pdev->dev, "unable to claim gpio \"kill\"\n");
191		return ret;
192	}
193
194	data->gpio_trigger = devm_gpiod_get_optional(&pdev->dev, "trigger",
195						     GPIOD_IN);
196	if (IS_ERR(data->gpio_trigger)) {
197		/*
198		 * It's not a problem if the trigger gpio isn't available, but
199		 * it is worth a warning if its use was defined in the device
200		 * tree.
201		 */
202		dev_err(&pdev->dev, "unable to claim gpio \"trigger\"\n");
203		data->gpio_trigger = NULL;
204	}
205
206	if (devm_request_irq(&pdev->dev, gpiod_to_irq(data->gpio_trigger),
207			     ltc2952_poweroff_handler,
208			     (IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING),
209			     "ltc2952-poweroff",
210			     data)) {
211		/*
212		 * Some things may have happened:
213		 * - No trigger input was defined
214		 * - Claiming the GPIO failed
215		 * - We could not map to an IRQ
216		 * - We couldn't register an interrupt handler
217		 *
218		 * None of these really are problems, but all of them
219		 * disqualify the push button from controlling the power.
220		 *
221		 * It is therefore important to note that if the ltc2952
222		 * detects a button press for long enough, it will still start
223		 * its own powerdown window and cut the power on us if we don't
224		 * start the watchdog trigger.
225		 */
226		if (data->gpio_trigger) {
227			dev_warn(&pdev->dev,
228				 "unable to configure the trigger interrupt\n");
229			devm_gpiod_put(&pdev->dev, data->gpio_trigger);
230			data->gpio_trigger = NULL;
231		}
232		dev_info(&pdev->dev,
233			 "power down trigger input will not be used\n");
234		ltc2952_poweroff_start_wde(data);
235	}
236
237	return 0;
238}
239
240static int ltc2952_poweroff_notify_panic(struct notifier_block *nb,
241					 unsigned long code, void *unused)
242{
243	struct ltc2952_poweroff *data = to_ltc2952(nb, panic_notifier);
244
245	data->kernel_panic = true;
246	return NOTIFY_DONE;
247}
248
249static int ltc2952_poweroff_probe(struct platform_device *pdev)
250{
251	int ret;
252	struct ltc2952_poweroff *data;
253
254	if (pm_power_off) {
255		dev_err(&pdev->dev, "pm_power_off already registered");
256		return -EBUSY;
257	}
258
259	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
260	if (!data)
261		return -ENOMEM;
262
263	data->dev = &pdev->dev;
264	platform_set_drvdata(pdev, data);
265
266	ret = ltc2952_poweroff_init(pdev);
267	if (ret)
268		return ret;
269
270	/* TODO: remove ltc2952_data */
271	ltc2952_data = data;
272	pm_power_off = ltc2952_poweroff_kill;
273
274	data->panic_notifier.notifier_call = ltc2952_poweroff_notify_panic;
275	atomic_notifier_chain_register(&panic_notifier_list,
276				       &data->panic_notifier);
277	dev_info(&pdev->dev, "probe successful\n");
278
279	return 0;
280}
281
282static int ltc2952_poweroff_remove(struct platform_device *pdev)
283{
284	struct ltc2952_poweroff *data = platform_get_drvdata(pdev);
285
286	pm_power_off = NULL;
287	hrtimer_cancel(&data->timer_trigger);
288	hrtimer_cancel(&data->timer_wde);
289	atomic_notifier_chain_unregister(&panic_notifier_list,
290					 &data->panic_notifier);
291	return 0;
292}
293
294static const struct of_device_id of_ltc2952_poweroff_match[] = {
295	{ .compatible = "lltc,ltc2952"},
296	{},
297};
298MODULE_DEVICE_TABLE(of, of_ltc2952_poweroff_match);
299
300static struct platform_driver ltc2952_poweroff_driver = {
301	.probe = ltc2952_poweroff_probe,
302	.remove = ltc2952_poweroff_remove,
303	.driver = {
304		.name = "ltc2952-poweroff",
305		.of_match_table = of_ltc2952_poweroff_match,
306	},
307};
308
309module_platform_driver(ltc2952_poweroff_driver);
310
311MODULE_AUTHOR("René Moll <rene.moll@xsens.com>");
312MODULE_DESCRIPTION("LTC PowerPath power-off driver");
313MODULE_LICENSE("GPL v2");
314