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/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 
61 struct 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  */
84 static 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  */
95 static 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 
111 static void ltc2952_poweroff_start_wde(struct ltc2952_poweroff *data)
112 {
113 	hrtimer_start(&data->timer_wde, data->wde_interval, HRTIMER_MODE_REL);
114 }
115 
116 static enum hrtimer_restart
117 ltc2952_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  */
137 static 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 
155 static void ltc2952_poweroff_kill(void)
156 {
157 	gpiod_set_value(ltc2952_data->gpio_kill, 1);
158 }
159 
160 static 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 
172 static 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 
247 static 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 
256 static 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 
289 static int 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 	return 0;
299 }
300 
301 static const struct of_device_id of_ltc2952_poweroff_match[] = {
302 	{ .compatible = "lltc,ltc2952"},
303 	{},
304 };
305 MODULE_DEVICE_TABLE(of, of_ltc2952_poweroff_match);
306 
307 static struct platform_driver ltc2952_poweroff_driver = {
308 	.probe = ltc2952_poweroff_probe,
309 	.remove = ltc2952_poweroff_remove,
310 	.driver = {
311 		.name = "ltc2952-poweroff",
312 		.of_match_table = of_ltc2952_poweroff_match,
313 	},
314 };
315 
316 module_platform_driver(ltc2952_poweroff_driver);
317 
318 MODULE_AUTHOR("René Moll <rene.moll@xsens.com>");
319 MODULE_DESCRIPTION("LTC PowerPath power-off driver");
320 MODULE_LICENSE("GPL v2");
321