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 
59 struct 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  */
82 static 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  */
93 static enum hrtimer_restart ltc2952_poweroff_timer_wde(struct hrtimer *timer)
94 {
95 	ktime_t now;
96 	int state;
97 	unsigned long overruns;
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 	now = hrtimer_cb_get_time(timer);
107 	overruns = hrtimer_forward(timer, now, data->wde_interval);
108 
109 	return HRTIMER_RESTART;
110 }
111 
112 static void ltc2952_poweroff_start_wde(struct ltc2952_poweroff *data)
113 {
114 	hrtimer_start(&data->timer_wde, data->wde_interval, HRTIMER_MODE_REL);
115 }
116 
117 static enum hrtimer_restart
118 ltc2952_poweroff_timer_trigger(struct hrtimer *timer)
119 {
120 	struct ltc2952_poweroff *data = to_ltc2952(timer, timer_trigger);
121 
122 	ltc2952_poweroff_start_wde(data);
123 	dev_info(data->dev, "executing shutdown\n");
124 	orderly_poweroff(true);
125 
126 	return HRTIMER_NORESTART;
127 }
128 
129 /**
130  * ltc2952_poweroff_handler - Interrupt handler
131  * Triggered each time the trigger signal changes state and (de)activates a
132  * time-out (timer_trigger). Once the time-out is actually reached the shut
133  * down is executed.
134  *
135  * @irq: IRQ number
136  * @dev_id: pointer to the main data structure
137  */
138 static irqreturn_t ltc2952_poweroff_handler(int irq, void *dev_id)
139 {
140 	struct ltc2952_poweroff *data = dev_id;
141 
142 	if (data->kernel_panic || hrtimer_active(&data->timer_wde)) {
143 		/* shutdown is already triggered, nothing to do any more */
144 		return IRQ_HANDLED;
145 	}
146 
147 	if (gpiod_get_value(data->gpio_trigger)) {
148 		hrtimer_start(&data->timer_trigger, data->trigger_delay,
149 			      HRTIMER_MODE_REL);
150 	} else {
151 		hrtimer_cancel(&data->timer_trigger);
152 	}
153 	return IRQ_HANDLED;
154 }
155 
156 static void ltc2952_poweroff_kill(void)
157 {
158 	gpiod_set_value(ltc2952_data->gpio_kill, 1);
159 }
160 
161 static void ltc2952_poweroff_default(struct ltc2952_poweroff *data)
162 {
163 	data->wde_interval = 300L * 1E6L;
164 	data->trigger_delay = ktime_set(2, 500L*1E6L);
165 
166 	hrtimer_init(&data->timer_trigger, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
167 	data->timer_trigger.function = ltc2952_poweroff_timer_trigger;
168 
169 	hrtimer_init(&data->timer_wde, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
170 	data->timer_wde.function = ltc2952_poweroff_timer_wde;
171 }
172 
173 static int ltc2952_poweroff_init(struct platform_device *pdev)
174 {
175 	int ret;
176 	struct ltc2952_poweroff *data = platform_get_drvdata(pdev);
177 
178 	ltc2952_poweroff_default(data);
179 
180 	data->gpio_watchdog = devm_gpiod_get(&pdev->dev, "watchdog",
181 					     GPIOD_OUT_LOW);
182 	if (IS_ERR(data->gpio_watchdog)) {
183 		ret = PTR_ERR(data->gpio_watchdog);
184 		dev_err(&pdev->dev, "unable to claim gpio \"watchdog\"\n");
185 		return ret;
186 	}
187 
188 	data->gpio_kill = devm_gpiod_get(&pdev->dev, "kill", GPIOD_OUT_LOW);
189 	if (IS_ERR(data->gpio_kill)) {
190 		ret = PTR_ERR(data->gpio_kill);
191 		dev_err(&pdev->dev, "unable to claim gpio \"kill\"\n");
192 		return ret;
193 	}
194 
195 	data->gpio_trigger = devm_gpiod_get_optional(&pdev->dev, "trigger",
196 						     GPIOD_IN);
197 	if (IS_ERR(data->gpio_trigger)) {
198 		/*
199 		 * It's not a problem if the trigger gpio isn't available, but
200 		 * it is worth a warning if its use was defined in the device
201 		 * tree.
202 		 */
203 		dev_err(&pdev->dev, "unable to claim gpio \"trigger\"\n");
204 		data->gpio_trigger = NULL;
205 	}
206 
207 	if (devm_request_irq(&pdev->dev, gpiod_to_irq(data->gpio_trigger),
208 			     ltc2952_poweroff_handler,
209 			     (IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING),
210 			     "ltc2952-poweroff",
211 			     data)) {
212 		/*
213 		 * Some things may have happened:
214 		 * - No trigger input was defined
215 		 * - Claiming the GPIO failed
216 		 * - We could not map to an IRQ
217 		 * - We couldn't register an interrupt handler
218 		 *
219 		 * None of these really are problems, but all of them
220 		 * disqualify the push button from controlling the power.
221 		 *
222 		 * It is therefore important to note that if the ltc2952
223 		 * detects a button press for long enough, it will still start
224 		 * its own powerdown window and cut the power on us if we don't
225 		 * start the watchdog trigger.
226 		 */
227 		if (data->gpio_trigger) {
228 			dev_warn(&pdev->dev,
229 				 "unable to configure the trigger interrupt\n");
230 			devm_gpiod_put(&pdev->dev, data->gpio_trigger);
231 			data->gpio_trigger = NULL;
232 		}
233 		dev_info(&pdev->dev,
234 			 "power down trigger input will not be used\n");
235 		ltc2952_poweroff_start_wde(data);
236 	}
237 
238 	return 0;
239 }
240 
241 static int ltc2952_poweroff_notify_panic(struct notifier_block *nb,
242 					 unsigned long code, void *unused)
243 {
244 	struct ltc2952_poweroff *data = to_ltc2952(nb, panic_notifier);
245 
246 	data->kernel_panic = true;
247 	return NOTIFY_DONE;
248 }
249 
250 static int ltc2952_poweroff_probe(struct platform_device *pdev)
251 {
252 	int ret;
253 	struct ltc2952_poweroff *data;
254 
255 	if (pm_power_off) {
256 		dev_err(&pdev->dev, "pm_power_off already registered");
257 		return -EBUSY;
258 	}
259 
260 	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
261 	if (!data)
262 		return -ENOMEM;
263 
264 	data->dev = &pdev->dev;
265 	platform_set_drvdata(pdev, data);
266 
267 	ret = ltc2952_poweroff_init(pdev);
268 	if (ret)
269 		return ret;
270 
271 	/* TODO: remove ltc2952_data */
272 	ltc2952_data = data;
273 	pm_power_off = ltc2952_poweroff_kill;
274 
275 	data->panic_notifier.notifier_call = ltc2952_poweroff_notify_panic;
276 	atomic_notifier_chain_register(&panic_notifier_list,
277 				       &data->panic_notifier);
278 	dev_info(&pdev->dev, "probe successful\n");
279 
280 	return 0;
281 }
282 
283 static int ltc2952_poweroff_remove(struct platform_device *pdev)
284 {
285 	struct ltc2952_poweroff *data = platform_get_drvdata(pdev);
286 
287 	pm_power_off = NULL;
288 	hrtimer_cancel(&data->timer_trigger);
289 	hrtimer_cancel(&data->timer_wde);
290 	atomic_notifier_chain_unregister(&panic_notifier_list,
291 					 &data->panic_notifier);
292 	return 0;
293 }
294 
295 static const struct of_device_id of_ltc2952_poweroff_match[] = {
296 	{ .compatible = "lltc,ltc2952"},
297 	{},
298 };
299 MODULE_DEVICE_TABLE(of, of_ltc2952_poweroff_match);
300 
301 static struct platform_driver ltc2952_poweroff_driver = {
302 	.probe = ltc2952_poweroff_probe,
303 	.remove = ltc2952_poweroff_remove,
304 	.driver = {
305 		.name = "ltc2952-poweroff",
306 		.of_match_table = of_ltc2952_poweroff_match,
307 	},
308 };
309 
310 module_platform_driver(ltc2952_poweroff_driver);
311 
312 MODULE_AUTHOR("René Moll <rene.moll@xsens.com>");
313 MODULE_DESCRIPTION("LTC PowerPath power-off driver");
314 MODULE_LICENSE("GPL v2");
315