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 	unsigned int virq;
76 
77 	/**
78 	 * 0: trigger
79 	 * 1: watchdog
80 	 * 2: kill
81 	 */
82 	struct gpio_desc *gpio[3];
83 };
84 
85 static int ltc2952_poweroff_panic;
86 static struct ltc2952_poweroff_data *ltc2952_data;
87 
88 #define POWERPATH_IO_TRIGGER	0
89 #define POWERPATH_IO_WATCHDOG	1
90 #define POWERPATH_IO_KILL	2
91 
92 /**
93  * ltc2952_poweroff_timer_wde - Timer callback
94  * Toggles the watchdog reset signal each wde_interval
95  *
96  * @timer: corresponding timer
97  *
98  * Returns HRTIMER_RESTART for an infinite loop which will only stop when the
99  * machine actually shuts down
100  */
101 static enum hrtimer_restart ltc2952_poweroff_timer_wde(struct hrtimer *timer)
102 {
103 	ktime_t now;
104 	int state;
105 	unsigned long overruns;
106 
107 	if (ltc2952_poweroff_panic)
108 		return HRTIMER_NORESTART;
109 
110 	state = gpiod_get_value(ltc2952_data->gpio[POWERPATH_IO_WATCHDOG]);
111 	gpiod_set_value(ltc2952_data->gpio[POWERPATH_IO_WATCHDOG], !state);
112 
113 	now = hrtimer_cb_get_time(timer);
114 	overruns = hrtimer_forward(timer, now, ltc2952_data->wde_interval);
115 
116 	return HRTIMER_RESTART;
117 }
118 
119 static enum hrtimer_restart ltc2952_poweroff_timer_trigger(
120 	struct hrtimer *timer)
121 {
122 	int ret;
123 
124 	ret = hrtimer_start(&ltc2952_data->timer_wde,
125 		ltc2952_data->wde_interval, HRTIMER_MODE_REL);
126 
127 	if (ret) {
128 		dev_err(ltc2952_data->dev, "unable to start the timer\n");
129 		/*
130 		 * The device will not toggle the watchdog reset,
131 		 * thus shut down is only safe if the PowerPath controller
132 		 * has a long enough time-off before triggering a hardware
133 		 * power-off.
134 		 *
135 		 * Only sending a warning as the system will power-off anyway
136 		 */
137 	}
138 
139 	dev_info(ltc2952_data->dev, "executing shutdown\n");
140 
141 	orderly_poweroff(true);
142 
143 	return HRTIMER_NORESTART;
144 }
145 
146 /**
147  * ltc2952_poweroff_handler - Interrupt handler
148  * Triggered each time the trigger signal changes state and (de)activates a
149  * time-out (timer_trigger). Once the time-out is actually reached the shut
150  * down is executed.
151  *
152  * @irq: IRQ number
153  * @dev_id: pointer to the main data structure
154  */
155 static irqreturn_t ltc2952_poweroff_handler(int irq, void *dev_id)
156 {
157 	int ret;
158 	struct ltc2952_poweroff_data *data = dev_id;
159 
160 	if (ltc2952_poweroff_panic)
161 		goto irq_ok;
162 
163 	if (hrtimer_active(&data->timer_wde)) {
164 		/* shutdown is already triggered, nothing to do any more */
165 		goto irq_ok;
166 	}
167 
168 	if (!hrtimer_active(&data->timer_trigger)) {
169 		ret = hrtimer_start(&data->timer_trigger, data->trigger_delay,
170 			HRTIMER_MODE_REL);
171 
172 		if (ret)
173 			dev_err(data->dev, "unable to start the wait timer\n");
174 	} else {
175 		ret = hrtimer_cancel(&data->timer_trigger);
176 		/* omitting return value check, timer should have been valid */
177 	}
178 
179 irq_ok:
180 	return IRQ_HANDLED;
181 }
182 
183 static void ltc2952_poweroff_kill(void)
184 {
185 	gpiod_set_value(ltc2952_data->gpio[POWERPATH_IO_KILL], 1);
186 }
187 
188 static int ltc2952_poweroff_suspend(struct platform_device *pdev,
189 	pm_message_t state)
190 {
191 	return -ENOSYS;
192 }
193 
194 static int ltc2952_poweroff_resume(struct platform_device *pdev)
195 {
196 	return -ENOSYS;
197 }
198 
199 static void ltc2952_poweroff_default(struct ltc2952_poweroff_data *data)
200 {
201 	unsigned int i;
202 
203 	for (i = 0; i < ARRAY_SIZE(data->gpio); i++)
204 		data->gpio[i] = NULL;
205 
206 	data->wde_interval = ktime_set(0, 300L*1E6L);
207 	data->trigger_delay = ktime_set(2, 500L*1E6L);
208 
209 	hrtimer_init(&data->timer_trigger, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
210 	data->timer_trigger.function = &ltc2952_poweroff_timer_trigger;
211 
212 	hrtimer_init(&data->timer_wde, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
213 	data->timer_wde.function = &ltc2952_poweroff_timer_wde;
214 }
215 
216 static int ltc2952_poweroff_init(struct platform_device *pdev)
217 {
218 	int ret, virq;
219 	unsigned int i;
220 	struct ltc2952_poweroff_data *data;
221 
222 	static char *name[] = {
223 		"trigger",
224 		"watchdog",
225 		"kill",
226 		NULL
227 	};
228 
229 	data = ltc2952_data;
230 	ltc2952_poweroff_default(ltc2952_data);
231 
232 	for (i = 0; i < ARRAY_SIZE(ltc2952_data->gpio); i++) {
233 		ltc2952_data->gpio[i] = gpiod_get(&pdev->dev, name[i]);
234 
235 		if (IS_ERR(ltc2952_data->gpio[i])) {
236 			ret = PTR_ERR(ltc2952_data->gpio[i]);
237 			dev_err(&pdev->dev,
238 				"unable to claim the following gpio: %s\n",
239 				name[i]);
240 			goto err_io;
241 		}
242 	}
243 
244 	ret = gpiod_direction_output(
245 		ltc2952_data->gpio[POWERPATH_IO_WATCHDOG], 0);
246 	if (ret) {
247 		dev_err(&pdev->dev, "unable to use watchdog-gpio as output\n");
248 		goto err_io;
249 	}
250 
251 	ret = gpiod_direction_output(ltc2952_data->gpio[POWERPATH_IO_KILL], 0);
252 	if (ret) {
253 		dev_err(&pdev->dev, "unable to use kill-gpio as output\n");
254 		goto err_io;
255 	}
256 
257 	virq = gpiod_to_irq(ltc2952_data->gpio[POWERPATH_IO_TRIGGER]);
258 	if (virq < 0) {
259 		dev_err(&pdev->dev, "cannot map GPIO as interrupt");
260 		goto err_io;
261 	}
262 
263 	ltc2952_data->virq = virq;
264 	ret = request_irq(virq,
265 		ltc2952_poweroff_handler,
266 		(IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING),
267 		"ltc2952-poweroff",
268 		ltc2952_data
269 	);
270 
271 	if (ret) {
272 		dev_err(&pdev->dev, "cannot configure an interrupt handler\n");
273 		goto err_io;
274 	}
275 
276 	return 0;
277 
278 err_io:
279 	for (i = 0; i < ARRAY_SIZE(ltc2952_data->gpio); i++)
280 		if (ltc2952_data->gpio[i])
281 			gpiod_put(ltc2952_data->gpio[i]);
282 
283 	return ret;
284 }
285 
286 static int ltc2952_poweroff_probe(struct platform_device *pdev)
287 {
288 	int ret;
289 
290 	if (pm_power_off) {
291 		dev_err(&pdev->dev, "pm_power_off already registered");
292 		return -EBUSY;
293 	}
294 
295 	ltc2952_data = kzalloc(sizeof(*ltc2952_data), GFP_KERNEL);
296 	if (!ltc2952_data)
297 		return -ENOMEM;
298 
299 	ltc2952_data->dev = &pdev->dev;
300 
301 	ret = ltc2952_poweroff_init(pdev);
302 	if (ret)
303 		goto err;
304 
305 	pm_power_off = &ltc2952_poweroff_kill;
306 
307 	dev_info(&pdev->dev, "probe successful\n");
308 
309 	return 0;
310 
311 err:
312 	kfree(ltc2952_data);
313 	return ret;
314 }
315 
316 static int ltc2952_poweroff_remove(struct platform_device *pdev)
317 {
318 	unsigned int i;
319 
320 	pm_power_off = NULL;
321 
322 	if (ltc2952_data) {
323 		free_irq(ltc2952_data->virq, ltc2952_data);
324 
325 		for (i = 0; i < ARRAY_SIZE(ltc2952_data->gpio); i++)
326 			gpiod_put(ltc2952_data->gpio[i]);
327 
328 		kfree(ltc2952_data);
329 	}
330 
331 	return 0;
332 }
333 
334 static const struct of_device_id of_ltc2952_poweroff_match[] = {
335 	{ .compatible = "lltc,ltc2952"},
336 	{},
337 };
338 MODULE_DEVICE_TABLE(of, of_ltc2952_poweroff_match);
339 
340 static struct platform_driver ltc2952_poweroff_driver = {
341 	.probe = ltc2952_poweroff_probe,
342 	.remove = ltc2952_poweroff_remove,
343 	.driver = {
344 		.name = "ltc2952-poweroff",
345 		.owner = THIS_MODULE,
346 		.of_match_table = of_ltc2952_poweroff_match,
347 	},
348 	.suspend = ltc2952_poweroff_suspend,
349 	.resume = ltc2952_poweroff_resume,
350 };
351 
352 static int ltc2952_poweroff_notify_panic(struct notifier_block *nb,
353 	unsigned long code, void *unused)
354 {
355 	ltc2952_poweroff_panic = 1;
356 	return NOTIFY_DONE;
357 }
358 
359 static struct notifier_block ltc2952_poweroff_panic_nb = {
360 	.notifier_call = ltc2952_poweroff_notify_panic,
361 };
362 
363 static int __init ltc2952_poweroff_platform_init(void)
364 {
365 	ltc2952_poweroff_panic = 0;
366 
367 	atomic_notifier_chain_register(&panic_notifier_list,
368 		&ltc2952_poweroff_panic_nb);
369 
370 	return platform_driver_register(&ltc2952_poweroff_driver);
371 }
372 
373 static void __exit ltc2952_poweroff_platform_exit(void)
374 {
375 	atomic_notifier_chain_unregister(&panic_notifier_list,
376 		&ltc2952_poweroff_panic_nb);
377 
378 	platform_driver_unregister(&ltc2952_poweroff_driver);
379 }
380 
381 module_init(ltc2952_poweroff_platform_init);
382 module_exit(ltc2952_poweroff_platform_exit);
383 
384 MODULE_AUTHOR("Ren� Moll <rene.moll@xsens.com>");
385 MODULE_DESCRIPTION("LTC PowerPath power-off driver");
386 MODULE_LICENSE("GPL v2");
387