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. If no pin is assigned to this input, the driver will start the
36  *     watchdog toggle immediately. The chip will only power off the system if
37  *     it is requested to do so through the kill line.
38  *
39  * - watchdog (output)
40  *     Once a shut down is triggered, the driver will toggle this signal,
41  *     with an internal (wde_interval) to stall the hardware shut down.
42  *
43  * - kill (output)
44  *     The last action during shut down is triggering this signalling, such
45  *     that the PowerPath Control will power down the hardware.
46  *
47  * ----------------------------------------
48  * - Interrupts
49  * ----------------------------------------
50  *
51  * The driver requires a non-shared, edge-triggered interrupt on the trigger
52  * GPIO.
53  *
54  */
55 
56 #include <linux/kernel.h>
57 #include <linux/init.h>
58 #include <linux/interrupt.h>
59 #include <linux/device.h>
60 #include <linux/platform_device.h>
61 #include <linux/ktime.h>
62 #include <linux/slab.h>
63 #include <linux/kmod.h>
64 #include <linux/module.h>
65 #include <linux/gpio/consumer.h>
66 #include <linux/reboot.h>
67 
68 struct ltc2952_poweroff {
69 	struct hrtimer timer_trigger;
70 	struct hrtimer timer_wde;
71 
72 	ktime_t trigger_delay;
73 	ktime_t wde_interval;
74 
75 	struct device *dev;
76 
77 	struct gpio_desc *gpio_trigger;
78 	struct gpio_desc *gpio_watchdog;
79 	struct gpio_desc *gpio_kill;
80 
81 	bool kernel_panic;
82 	struct notifier_block panic_notifier;
83 };
84 
85 #define to_ltc2952(p, m) container_of(p, struct ltc2952_poweroff, m)
86 
87 /*
88  * This global variable is only needed for pm_power_off. We should
89  * remove it entirely once we don't need the global state anymore.
90  */
91 static struct ltc2952_poweroff *ltc2952_data;
92 
93 /**
94  * ltc2952_poweroff_timer_wde - Timer callback
95  * Toggles the watchdog reset signal each wde_interval
96  *
97  * @timer: corresponding timer
98  *
99  * Returns HRTIMER_RESTART for an infinite loop which will only stop when the
100  * machine actually shuts down
101  */
102 static enum hrtimer_restart ltc2952_poweroff_timer_wde(struct hrtimer *timer)
103 {
104 	ktime_t now;
105 	int state;
106 	unsigned long overruns;
107 	struct ltc2952_poweroff *data = to_ltc2952(timer, timer_wde);
108 
109 	if (data->kernel_panic)
110 		return HRTIMER_NORESTART;
111 
112 	state = gpiod_get_value(data->gpio_watchdog);
113 	gpiod_set_value(data->gpio_watchdog, !state);
114 
115 	now = hrtimer_cb_get_time(timer);
116 	overruns = hrtimer_forward(timer, now, data->wde_interval);
117 
118 	return HRTIMER_RESTART;
119 }
120 
121 static void ltc2952_poweroff_start_wde(struct ltc2952_poweroff *data)
122 {
123 	hrtimer_start(&data->timer_wde, data->wde_interval, HRTIMER_MODE_REL);
124 }
125 
126 static enum hrtimer_restart
127 ltc2952_poweroff_timer_trigger(struct hrtimer *timer)
128 {
129 	struct ltc2952_poweroff *data = to_ltc2952(timer, timer_trigger);
130 
131 	ltc2952_poweroff_start_wde(data);
132 	dev_info(data->dev, "executing shutdown\n");
133 	orderly_poweroff(true);
134 
135 	return HRTIMER_NORESTART;
136 }
137 
138 /**
139  * ltc2952_poweroff_handler - Interrupt handler
140  * Triggered each time the trigger signal changes state and (de)activates a
141  * time-out (timer_trigger). Once the time-out is actually reached the shut
142  * down is executed.
143  *
144  * @irq: IRQ number
145  * @dev_id: pointer to the main data structure
146  */
147 static irqreturn_t ltc2952_poweroff_handler(int irq, void *dev_id)
148 {
149 	struct ltc2952_poweroff *data = dev_id;
150 
151 	if (data->kernel_panic || hrtimer_active(&data->timer_wde)) {
152 		/* shutdown is already triggered, nothing to do any more */
153 		return IRQ_HANDLED;
154 	}
155 
156 	if (gpiod_get_value(data->gpio_trigger)) {
157 		hrtimer_start(&data->timer_trigger, data->trigger_delay,
158 			      HRTIMER_MODE_REL);
159 	} else {
160 		hrtimer_cancel(&data->timer_trigger);
161 	}
162 	return IRQ_HANDLED;
163 }
164 
165 static void ltc2952_poweroff_kill(void)
166 {
167 	gpiod_set_value(ltc2952_data->gpio_kill, 1);
168 }
169 
170 static void ltc2952_poweroff_default(struct ltc2952_poweroff *data)
171 {
172 	data->wde_interval = ktime_set(0, 300L*1E6L);
173 	data->trigger_delay = ktime_set(2, 500L*1E6L);
174 
175 	hrtimer_init(&data->timer_trigger, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
176 	data->timer_trigger.function = ltc2952_poweroff_timer_trigger;
177 
178 	hrtimer_init(&data->timer_wde, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
179 	data->timer_wde.function = ltc2952_poweroff_timer_wde;
180 }
181 
182 static int ltc2952_poweroff_init(struct platform_device *pdev)
183 {
184 	int ret;
185 	struct ltc2952_poweroff *data = platform_get_drvdata(pdev);
186 
187 	ltc2952_poweroff_default(data);
188 
189 	data->gpio_watchdog = devm_gpiod_get(&pdev->dev, "watchdog",
190 					     GPIOD_OUT_LOW);
191 	if (IS_ERR(data->gpio_watchdog)) {
192 		ret = PTR_ERR(data->gpio_watchdog);
193 		dev_err(&pdev->dev, "unable to claim gpio \"watchdog\"\n");
194 		return ret;
195 	}
196 
197 	data->gpio_kill = devm_gpiod_get(&pdev->dev, "kill", GPIOD_OUT_LOW);
198 	if (IS_ERR(data->gpio_kill)) {
199 		ret = PTR_ERR(data->gpio_kill);
200 		dev_err(&pdev->dev, "unable to claim gpio \"kill\"\n");
201 		return ret;
202 	}
203 
204 	data->gpio_trigger = devm_gpiod_get_optional(&pdev->dev, "trigger",
205 						     GPIOD_IN);
206 	if (IS_ERR(data->gpio_trigger)) {
207 		/*
208 		 * It's not a problem if the trigger gpio isn't available, but
209 		 * it is worth a warning if its use was defined in the device
210 		 * tree.
211 		 */
212 		dev_err(&pdev->dev, "unable to claim gpio \"trigger\"\n");
213 		data->gpio_trigger = NULL;
214 	}
215 
216 	if (devm_request_irq(&pdev->dev, gpiod_to_irq(data->gpio_trigger),
217 			     ltc2952_poweroff_handler,
218 			     (IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING),
219 			     "ltc2952-poweroff",
220 			     data)) {
221 		/*
222 		 * Some things may have happened:
223 		 * - No trigger input was defined
224 		 * - Claiming the GPIO failed
225 		 * - We could not map to an IRQ
226 		 * - We couldn't register an interrupt handler
227 		 *
228 		 * None of these really are problems, but all of them
229 		 * disqualify the push button from controlling the power.
230 		 *
231 		 * It is therefore important to note that if the ltc2952
232 		 * detects a button press for long enough, it will still start
233 		 * its own powerdown window and cut the power on us if we don't
234 		 * start the watchdog trigger.
235 		 */
236 		if (data->gpio_trigger) {
237 			dev_warn(&pdev->dev,
238 				 "unable to configure the trigger interrupt\n");
239 			devm_gpiod_put(&pdev->dev, data->gpio_trigger);
240 			data->gpio_trigger = NULL;
241 		}
242 		dev_info(&pdev->dev,
243 			 "power down trigger input will not be used\n");
244 		ltc2952_poweroff_start_wde(data);
245 	}
246 
247 	return 0;
248 }
249 
250 static int ltc2952_poweroff_notify_panic(struct notifier_block *nb,
251 					 unsigned long code, void *unused)
252 {
253 	struct ltc2952_poweroff *data = to_ltc2952(nb, panic_notifier);
254 
255 	data->kernel_panic = true;
256 	return NOTIFY_DONE;
257 }
258 
259 static int ltc2952_poweroff_probe(struct platform_device *pdev)
260 {
261 	int ret;
262 	struct ltc2952_poweroff *data;
263 
264 	if (pm_power_off) {
265 		dev_err(&pdev->dev, "pm_power_off already registered");
266 		return -EBUSY;
267 	}
268 
269 	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
270 	if (!data)
271 		return -ENOMEM;
272 
273 	data->dev = &pdev->dev;
274 	platform_set_drvdata(pdev, data);
275 
276 	ret = ltc2952_poweroff_init(pdev);
277 	if (ret)
278 		return ret;
279 
280 	/* TODO: remove ltc2952_data */
281 	ltc2952_data = data;
282 	pm_power_off = ltc2952_poweroff_kill;
283 
284 	data->panic_notifier.notifier_call = ltc2952_poweroff_notify_panic;
285 	atomic_notifier_chain_register(&panic_notifier_list,
286 				       &data->panic_notifier);
287 	dev_info(&pdev->dev, "probe successful\n");
288 
289 	return 0;
290 }
291 
292 static int ltc2952_poweroff_remove(struct platform_device *pdev)
293 {
294 	struct ltc2952_poweroff *data = platform_get_drvdata(pdev);
295 
296 	pm_power_off = NULL;
297 	hrtimer_cancel(&data->timer_trigger);
298 	hrtimer_cancel(&data->timer_wde);
299 	atomic_notifier_chain_unregister(&panic_notifier_list,
300 					 &data->panic_notifier);
301 	return 0;
302 }
303 
304 static const struct of_device_id of_ltc2952_poweroff_match[] = {
305 	{ .compatible = "lltc,ltc2952"},
306 	{},
307 };
308 MODULE_DEVICE_TABLE(of, of_ltc2952_poweroff_match);
309 
310 static struct platform_driver ltc2952_poweroff_driver = {
311 	.probe = ltc2952_poweroff_probe,
312 	.remove = ltc2952_poweroff_remove,
313 	.driver = {
314 		.name = "ltc2952-poweroff",
315 		.of_match_table = of_ltc2952_poweroff_match,
316 	},
317 };
318 
319 module_platform_driver(ltc2952_poweroff_driver);
320 
321 MODULE_AUTHOR("Ren� Moll <rene.moll@xsens.com>");
322 MODULE_DESCRIPTION("LTC PowerPath power-off driver");
323 MODULE_LICENSE("GPL v2");
324