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.
36  *
37  * - watchdog (output)
38  *     Once a shut down is triggered, the driver will toggle this signal,
39  *     with an internal (wde_interval) to stall the hardware shut down.
40  *
41  * - kill (output)
42  *     The last action during shut down is triggering this signalling, such
43  *     that the PowerPath Control will power down the hardware.
44  *
45  * ----------------------------------------
46  * - Interrupts
47  * ----------------------------------------
48  *
49  * The driver requires a non-shared, edge-triggered interrupt on the trigger
50  * GPIO.
51  *
52  */
53 
54 #include <linux/kernel.h>
55 #include <linux/init.h>
56 #include <linux/interrupt.h>
57 #include <linux/device.h>
58 #include <linux/platform_device.h>
59 #include <linux/ktime.h>
60 #include <linux/slab.h>
61 #include <linux/kmod.h>
62 #include <linux/module.h>
63 #include <linux/gpio/consumer.h>
64 #include <linux/reboot.h>
65 
66 struct ltc2952_poweroff_data {
67 	struct hrtimer timer_trigger;
68 	struct hrtimer timer_wde;
69 
70 	ktime_t trigger_delay;
71 	ktime_t wde_interval;
72 
73 	struct device *dev;
74 
75 	/**
76 	 * 0: trigger
77 	 * 1: watchdog
78 	 * 2: kill
79 	 */
80 	struct gpio_desc *gpio[3];
81 };
82 
83 static int ltc2952_poweroff_panic;
84 static struct ltc2952_poweroff_data *ltc2952_data;
85 
86 #define POWERPATH_IO_TRIGGER	0
87 #define POWERPATH_IO_WATCHDOG	1
88 #define POWERPATH_IO_KILL	2
89 
90 /**
91  * ltc2952_poweroff_timer_wde - Timer callback
92  * Toggles the watchdog reset signal each wde_interval
93  *
94  * @timer: corresponding timer
95  *
96  * Returns HRTIMER_RESTART for an infinite loop which will only stop when the
97  * machine actually shuts down
98  */
99 static enum hrtimer_restart ltc2952_poweroff_timer_wde(struct hrtimer *timer)
100 {
101 	ktime_t now;
102 	int state;
103 	unsigned long overruns;
104 
105 	if (ltc2952_poweroff_panic)
106 		return HRTIMER_NORESTART;
107 
108 	state = gpiod_get_value(ltc2952_data->gpio[POWERPATH_IO_WATCHDOG]);
109 	gpiod_set_value(ltc2952_data->gpio[POWERPATH_IO_WATCHDOG], !state);
110 
111 	now = hrtimer_cb_get_time(timer);
112 	overruns = hrtimer_forward(timer, now, ltc2952_data->wde_interval);
113 
114 	return HRTIMER_RESTART;
115 }
116 
117 static enum hrtimer_restart ltc2952_poweroff_timer_trigger(
118 	struct hrtimer *timer)
119 {
120 	int ret;
121 
122 	ret = hrtimer_start(&ltc2952_data->timer_wde,
123 		ltc2952_data->wde_interval, HRTIMER_MODE_REL);
124 
125 	if (ret) {
126 		dev_err(ltc2952_data->dev, "unable to start the timer\n");
127 		/*
128 		 * The device will not toggle the watchdog reset,
129 		 * thus shut down is only safe if the PowerPath controller
130 		 * has a long enough time-off before triggering a hardware
131 		 * power-off.
132 		 *
133 		 * Only sending a warning as the system will power-off anyway
134 		 */
135 	}
136 
137 	dev_info(ltc2952_data->dev, "executing shutdown\n");
138 
139 	orderly_poweroff(true);
140 
141 	return HRTIMER_NORESTART;
142 }
143 
144 /**
145  * ltc2952_poweroff_handler - Interrupt handler
146  * Triggered each time the trigger signal changes state and (de)activates a
147  * time-out (timer_trigger). Once the time-out is actually reached the shut
148  * down is executed.
149  *
150  * @irq: IRQ number
151  * @dev_id: pointer to the main data structure
152  */
153 static irqreturn_t ltc2952_poweroff_handler(int irq, void *dev_id)
154 {
155 	int ret;
156 	struct ltc2952_poweroff_data *data = dev_id;
157 
158 	if (ltc2952_poweroff_panic)
159 		goto irq_ok;
160 
161 	if (hrtimer_active(&data->timer_wde)) {
162 		/* shutdown is already triggered, nothing to do any more */
163 		goto irq_ok;
164 	}
165 
166 	if (!hrtimer_active(&data->timer_trigger)) {
167 		ret = hrtimer_start(&data->timer_trigger, data->trigger_delay,
168 			HRTIMER_MODE_REL);
169 
170 		if (ret)
171 			dev_err(data->dev, "unable to start the wait timer\n");
172 	} else {
173 		ret = hrtimer_cancel(&data->timer_trigger);
174 		/* omitting return value check, timer should have been valid */
175 	}
176 
177 irq_ok:
178 	return IRQ_HANDLED;
179 }
180 
181 static void ltc2952_poweroff_kill(void)
182 {
183 	gpiod_set_value(ltc2952_data->gpio[POWERPATH_IO_KILL], 1);
184 }
185 
186 static int ltc2952_poweroff_suspend(struct platform_device *pdev,
187 	pm_message_t state)
188 {
189 	return -ENOSYS;
190 }
191 
192 static int ltc2952_poweroff_resume(struct platform_device *pdev)
193 {
194 	return -ENOSYS;
195 }
196 
197 static void ltc2952_poweroff_default(struct ltc2952_poweroff_data *data)
198 {
199 	unsigned int i;
200 
201 	for (i = 0; i < ARRAY_SIZE(data->gpio); i++)
202 		data->gpio[i] = NULL;
203 
204 	data->wde_interval = ktime_set(0, 300L*1E6L);
205 	data->trigger_delay = ktime_set(2, 500L*1E6L);
206 
207 	hrtimer_init(&data->timer_trigger, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
208 	data->timer_trigger.function = &ltc2952_poweroff_timer_trigger;
209 
210 	hrtimer_init(&data->timer_wde, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
211 	data->timer_wde.function = &ltc2952_poweroff_timer_wde;
212 }
213 
214 static int ltc2952_poweroff_init(struct platform_device *pdev)
215 {
216 	int ret, virq;
217 	unsigned int i;
218 	struct ltc2952_poweroff_data *data;
219 
220 	static char *name[] = {
221 		"trigger",
222 		"watchdog",
223 		"kill",
224 		NULL
225 	};
226 
227 	data = ltc2952_data;
228 	ltc2952_poweroff_default(ltc2952_data);
229 
230 	for (i = 0; i < ARRAY_SIZE(ltc2952_data->gpio); i++) {
231 		ltc2952_data->gpio[i] = gpiod_get(&pdev->dev, name[i]);
232 
233 		if (IS_ERR(ltc2952_data->gpio[i])) {
234 			ret = PTR_ERR(ltc2952_data->gpio[i]);
235 			dev_err(&pdev->dev,
236 				"unable to claim the following gpio: %s\n",
237 				name[i]);
238 			goto err_io;
239 		}
240 	}
241 
242 	ret = gpiod_direction_output(
243 		ltc2952_data->gpio[POWERPATH_IO_WATCHDOG], 0);
244 	if (ret) {
245 		dev_err(&pdev->dev, "unable to use watchdog-gpio as output\n");
246 		goto err_io;
247 	}
248 
249 	ret = gpiod_direction_output(ltc2952_data->gpio[POWERPATH_IO_KILL], 0);
250 	if (ret) {
251 		dev_err(&pdev->dev, "unable to use kill-gpio as output\n");
252 		goto err_io;
253 	}
254 
255 	virq = gpiod_to_irq(ltc2952_data->gpio[POWERPATH_IO_TRIGGER]);
256 	if (virq < 0) {
257 		dev_err(&pdev->dev, "cannot map GPIO as interrupt");
258 		goto err_io;
259 	}
260 
261 	ret = devm_request_irq(&pdev->dev, virq,
262 			       ltc2952_poweroff_handler,
263 			       (IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING),
264 			       "ltc2952-poweroff",
265 			       ltc2952_data);
266 
267 	if (ret) {
268 		dev_err(&pdev->dev, "cannot configure an interrupt handler\n");
269 		goto err_io;
270 	}
271 
272 	return 0;
273 
274 err_io:
275 	for (i = 0; i < ARRAY_SIZE(ltc2952_data->gpio); i++)
276 		if (ltc2952_data->gpio[i])
277 			gpiod_put(ltc2952_data->gpio[i]);
278 
279 	return ret;
280 }
281 
282 static int ltc2952_poweroff_probe(struct platform_device *pdev)
283 {
284 	int ret;
285 
286 	if (pm_power_off) {
287 		dev_err(&pdev->dev, "pm_power_off already registered");
288 		return -EBUSY;
289 	}
290 
291 	ltc2952_data = devm_kzalloc(&pdev->dev, sizeof(*ltc2952_data),
292 				    GFP_KERNEL);
293 	if (!ltc2952_data)
294 		return -ENOMEM;
295 
296 	ltc2952_data->dev = &pdev->dev;
297 
298 	ret = ltc2952_poweroff_init(pdev);
299 	if (ret)
300 		return ret;
301 
302 	pm_power_off = &ltc2952_poweroff_kill;
303 
304 	dev_info(&pdev->dev, "probe successful\n");
305 
306 	return 0;
307 }
308 
309 static int ltc2952_poweroff_remove(struct platform_device *pdev)
310 {
311 	unsigned int i;
312 
313 	pm_power_off = NULL;
314 
315 	if (ltc2952_data)
316 		for (i = 0; i < ARRAY_SIZE(ltc2952_data->gpio); i++)
317 			gpiod_put(ltc2952_data->gpio[i]);
318 
319 	return 0;
320 }
321 
322 static const struct of_device_id of_ltc2952_poweroff_match[] = {
323 	{ .compatible = "lltc,ltc2952"},
324 	{},
325 };
326 MODULE_DEVICE_TABLE(of, of_ltc2952_poweroff_match);
327 
328 static struct platform_driver ltc2952_poweroff_driver = {
329 	.probe = ltc2952_poweroff_probe,
330 	.remove = ltc2952_poweroff_remove,
331 	.driver = {
332 		.name = "ltc2952-poweroff",
333 		.of_match_table = of_ltc2952_poweroff_match,
334 	},
335 	.suspend = ltc2952_poweroff_suspend,
336 	.resume = ltc2952_poweroff_resume,
337 };
338 
339 static int ltc2952_poweroff_notify_panic(struct notifier_block *nb,
340 	unsigned long code, void *unused)
341 {
342 	ltc2952_poweroff_panic = 1;
343 	return NOTIFY_DONE;
344 }
345 
346 static struct notifier_block ltc2952_poweroff_panic_nb = {
347 	.notifier_call = ltc2952_poweroff_notify_panic,
348 };
349 
350 static int __init ltc2952_poweroff_platform_init(void)
351 {
352 	ltc2952_poweroff_panic = 0;
353 
354 	atomic_notifier_chain_register(&panic_notifier_list,
355 		&ltc2952_poweroff_panic_nb);
356 
357 	return platform_driver_register(&ltc2952_poweroff_driver);
358 }
359 
360 static void __exit ltc2952_poweroff_platform_exit(void)
361 {
362 	atomic_notifier_chain_unregister(&panic_notifier_list,
363 		&ltc2952_poweroff_panic_nb);
364 
365 	platform_driver_unregister(&ltc2952_poweroff_driver);
366 }
367 
368 module_init(ltc2952_poweroff_platform_init);
369 module_exit(ltc2952_poweroff_platform_exit);
370 
371 MODULE_AUTHOR("Ren� Moll <rene.moll@xsens.com>");
372 MODULE_DESCRIPTION("LTC PowerPath power-off driver");
373 MODULE_LICENSE("GPL v2");
374