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: Ren�� 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/panic_notifier.h>
56#include <linux/mod_devicetable.h>
57#include <linux/gpio/consumer.h>
58#include <linux/reboot.h>
59#include <linux/property.h>
60
61struct ltc2952_poweroff {
62	struct hrtimer timer_trigger;
63	struct hrtimer timer_wde;
64
65	ktime_t trigger_delay;
66	ktime_t wde_interval;
67
68	struct device *dev;
69
70	struct gpio_desc *gpio_trigger;
71	struct gpio_desc *gpio_watchdog;
72	struct gpio_desc *gpio_kill;
73
74	bool kernel_panic;
75	struct notifier_block panic_notifier;
76};
77
78#define to_ltc2952(p, m) container_of(p, struct ltc2952_poweroff, m)
79
80/*
81 * This global variable is only needed for pm_power_off. We should
82 * remove it entirely once we don't need the global state anymore.
83 */
84static struct ltc2952_poweroff *ltc2952_data;
85
86/**
87 * ltc2952_poweroff_timer_wde - Timer callback
88 * Toggles the watchdog reset signal each wde_interval
89 *
90 * @timer: corresponding timer
91 *
92 * Returns HRTIMER_RESTART for an infinite loop which will only stop when the
93 * machine actually shuts down
94 */
95static enum hrtimer_restart ltc2952_poweroff_timer_wde(struct hrtimer *timer)
96{
97	int state;
98	struct ltc2952_poweroff *data = to_ltc2952(timer, timer_wde);
99
100	if (data->kernel_panic)
101		return HRTIMER_NORESTART;
102
103	state = gpiod_get_value(data->gpio_watchdog);
104	gpiod_set_value(data->gpio_watchdog, !state);
105
106	hrtimer_forward_now(timer, 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	u32 trigger_delay_ms;
176	struct ltc2952_poweroff *data = platform_get_drvdata(pdev);
177
178	ltc2952_poweroff_default(data);
179
180	if (!device_property_read_u32(&pdev->dev, "trigger-delay-ms",
181				      &trigger_delay_ms)) {
182		data->trigger_delay = ktime_set(trigger_delay_ms / MSEC_PER_SEC,
183			(trigger_delay_ms % MSEC_PER_SEC) * NSEC_PER_MSEC);
184	}
185
186	data->gpio_watchdog = devm_gpiod_get(&pdev->dev, "watchdog",
187					     GPIOD_OUT_LOW);
188	if (IS_ERR(data->gpio_watchdog)) {
189		ret = PTR_ERR(data->gpio_watchdog);
190		dev_err(&pdev->dev, "unable to claim gpio \"watchdog\"\n");
191		return ret;
192	}
193
194	data->gpio_kill = devm_gpiod_get(&pdev->dev, "kill", GPIOD_OUT_LOW);
195	if (IS_ERR(data->gpio_kill)) {
196		ret = PTR_ERR(data->gpio_kill);
197		dev_err(&pdev->dev, "unable to claim gpio \"kill\"\n");
198		return ret;
199	}
200
201	data->gpio_trigger = devm_gpiod_get_optional(&pdev->dev, "trigger",
202						     GPIOD_IN);
203	if (IS_ERR(data->gpio_trigger)) {
204		/*
205		 * It's not a problem if the trigger gpio isn't available, but
206		 * it is worth a warning if its use was defined in the device
207		 * tree.
208		 */
209		dev_err(&pdev->dev, "unable to claim gpio \"trigger\"\n");
210		data->gpio_trigger = NULL;
211	}
212
213	if (devm_request_irq(&pdev->dev, gpiod_to_irq(data->gpio_trigger),
214			     ltc2952_poweroff_handler,
215			     (IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING),
216			     "ltc2952-poweroff",
217			     data)) {
218		/*
219		 * Some things may have happened:
220		 * - No trigger input was defined
221		 * - Claiming the GPIO failed
222		 * - We could not map to an IRQ
223		 * - We couldn't register an interrupt handler
224		 *
225		 * None of these really are problems, but all of them
226		 * disqualify the push button from controlling the power.
227		 *
228		 * It is therefore important to note that if the ltc2952
229		 * detects a button press for long enough, it will still start
230		 * its own powerdown window and cut the power on us if we don't
231		 * start the watchdog trigger.
232		 */
233		if (data->gpio_trigger) {
234			dev_warn(&pdev->dev,
235				 "unable to configure the trigger interrupt\n");
236			devm_gpiod_put(&pdev->dev, data->gpio_trigger);
237			data->gpio_trigger = NULL;
238		}
239		dev_info(&pdev->dev,
240			 "power down trigger input will not be used\n");
241		ltc2952_poweroff_start_wde(data);
242	}
243
244	return 0;
245}
246
247static int ltc2952_poweroff_notify_panic(struct notifier_block *nb,
248					 unsigned long code, void *unused)
249{
250	struct ltc2952_poweroff *data = to_ltc2952(nb, panic_notifier);
251
252	data->kernel_panic = true;
253	return NOTIFY_DONE;
254}
255
256static int ltc2952_poweroff_probe(struct platform_device *pdev)
257{
258	int ret;
259	struct ltc2952_poweroff *data;
260
261	if (pm_power_off) {
262		dev_err(&pdev->dev, "pm_power_off already registered");
263		return -EBUSY;
264	}
265
266	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
267	if (!data)
268		return -ENOMEM;
269
270	data->dev = &pdev->dev;
271	platform_set_drvdata(pdev, data);
272
273	ret = ltc2952_poweroff_init(pdev);
274	if (ret)
275		return ret;
276
277	/* TODO: remove ltc2952_data */
278	ltc2952_data = data;
279	pm_power_off = ltc2952_poweroff_kill;
280
281	data->panic_notifier.notifier_call = ltc2952_poweroff_notify_panic;
282	atomic_notifier_chain_register(&panic_notifier_list,
283				       &data->panic_notifier);
284	dev_info(&pdev->dev, "probe successful\n");
285
286	return 0;
287}
288
289static void ltc2952_poweroff_remove(struct platform_device *pdev)
290{
291	struct ltc2952_poweroff *data = platform_get_drvdata(pdev);
292
293	pm_power_off = NULL;
294	hrtimer_cancel(&data->timer_trigger);
295	hrtimer_cancel(&data->timer_wde);
296	atomic_notifier_chain_unregister(&panic_notifier_list,
297					 &data->panic_notifier);
298}
299
300static const struct of_device_id of_ltc2952_poweroff_match[] = {
301	{ .compatible = "lltc,ltc2952"},
302	{},
303};
304MODULE_DEVICE_TABLE(of, of_ltc2952_poweroff_match);
305
306static struct platform_driver ltc2952_poweroff_driver = {
307	.probe = ltc2952_poweroff_probe,
308	.remove_new = ltc2952_poweroff_remove,
309	.driver = {
310		.name = "ltc2952-poweroff",
311		.of_match_table = of_ltc2952_poweroff_match,
312	},
313};
314
315module_platform_driver(ltc2952_poweroff_driver);
316
317MODULE_AUTHOR("Ren�� Moll <rene.moll@xsens.com>");
318MODULE_DESCRIPTION("LTC PowerPath power-off driver");
319