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 {
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 	struct gpio_desc *gpio_trigger;
76 	struct gpio_desc *gpio_watchdog;
77 	struct gpio_desc *gpio_kill;
78 
79 	bool kernel_panic;
80 	struct notifier_block panic_notifier;
81 };
82 
83 #define to_ltc2952(p, m) container_of(p, struct ltc2952_poweroff, m)
84 
85 /*
86  * This global variable is only needed for pm_power_off. We should
87  * remove it entirely once we don't need the global state anymore.
88  */
89 static struct ltc2952_poweroff *ltc2952_data;
90 
91 /**
92  * ltc2952_poweroff_timer_wde - Timer callback
93  * Toggles the watchdog reset signal each wde_interval
94  *
95  * @timer: corresponding timer
96  *
97  * Returns HRTIMER_RESTART for an infinite loop which will only stop when the
98  * machine actually shuts down
99  */
100 static enum hrtimer_restart ltc2952_poweroff_timer_wde(struct hrtimer *timer)
101 {
102 	ktime_t now;
103 	int state;
104 	unsigned long overruns;
105 	struct ltc2952_poweroff *data = to_ltc2952(timer, timer_wde);
106 
107 	if (data->kernel_panic)
108 		return HRTIMER_NORESTART;
109 
110 	state = gpiod_get_value(data->gpio_watchdog);
111 	gpiod_set_value(data->gpio_watchdog, !state);
112 
113 	now = hrtimer_cb_get_time(timer);
114 	overruns = hrtimer_forward(timer, now, data->wde_interval);
115 
116 	return HRTIMER_RESTART;
117 }
118 
119 static enum hrtimer_restart
120 ltc2952_poweroff_timer_trigger(struct hrtimer *timer)
121 {
122 	struct ltc2952_poweroff *data = to_ltc2952(timer, timer_trigger);
123 	int ret = hrtimer_start(&data->timer_wde,
124 				data->wde_interval, HRTIMER_MODE_REL);
125 
126 	if (ret) {
127 		dev_err(data->dev, "unable to start the timer\n");
128 		/*
129 		 * The device will not toggle the watchdog reset,
130 		 * thus shut down is only safe if the PowerPath controller
131 		 * has a long enough time-off before triggering a hardware
132 		 * power-off.
133 		 *
134 		 * Only sending a warning as the system will power-off anyway
135 		 */
136 	}
137 
138 	dev_info(data->dev, "executing shutdown\n");
139 
140 	orderly_poweroff(true);
141 
142 	return HRTIMER_NORESTART;
143 }
144 
145 /**
146  * ltc2952_poweroff_handler - Interrupt handler
147  * Triggered each time the trigger signal changes state and (de)activates a
148  * time-out (timer_trigger). Once the time-out is actually reached the shut
149  * down is executed.
150  *
151  * @irq: IRQ number
152  * @dev_id: pointer to the main data structure
153  */
154 static irqreturn_t ltc2952_poweroff_handler(int irq, void *dev_id)
155 {
156 	int ret;
157 	struct ltc2952_poweroff *data = dev_id;
158 
159 	if (data->kernel_panic)
160 		goto irq_ok;
161 
162 	if (hrtimer_active(&data->timer_wde)) {
163 		/* shutdown is already triggered, nothing to do any more */
164 		goto irq_ok;
165 	}
166 
167 	if (!hrtimer_active(&data->timer_trigger)) {
168 		ret = hrtimer_start(&data->timer_trigger, data->trigger_delay,
169 			HRTIMER_MODE_REL);
170 
171 		if (ret)
172 			dev_err(data->dev, "unable to start the wait timer\n");
173 	} else {
174 		ret = hrtimer_cancel(&data->timer_trigger);
175 		/* omitting return value check, timer should have been valid */
176 	}
177 
178 irq_ok:
179 	return IRQ_HANDLED;
180 }
181 
182 static void ltc2952_poweroff_kill(void)
183 {
184 	gpiod_set_value(ltc2952_data->gpio_kill, 1);
185 }
186 
187 static void ltc2952_poweroff_default(struct ltc2952_poweroff *data)
188 {
189 	data->wde_interval = ktime_set(0, 300L*1E6L);
190 	data->trigger_delay = ktime_set(2, 500L*1E6L);
191 
192 	hrtimer_init(&data->timer_trigger, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
193 	data->timer_trigger.function = &ltc2952_poweroff_timer_trigger;
194 
195 	hrtimer_init(&data->timer_wde, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
196 	data->timer_wde.function = &ltc2952_poweroff_timer_wde;
197 }
198 
199 static int ltc2952_poweroff_init(struct platform_device *pdev)
200 {
201 	int ret, virq;
202 	struct ltc2952_poweroff *data = platform_get_drvdata(pdev);
203 
204 	ltc2952_poweroff_default(data);
205 
206 	data->gpio_watchdog = devm_gpiod_get(&pdev->dev, "watchdog",
207 					     GPIOD_OUT_LOW);
208 	if (IS_ERR(data->gpio_watchdog)) {
209 		ret = PTR_ERR(data->gpio_watchdog);
210 		dev_err(&pdev->dev, "unable to claim gpio \"watchdog\"\n");
211 		return ret;
212 	}
213 
214 	data->gpio_kill = devm_gpiod_get(&pdev->dev, "kill", GPIOD_OUT_LOW);
215 	if (IS_ERR(data->gpio_kill)) {
216 		ret = PTR_ERR(data->gpio_kill);
217 		dev_err(&pdev->dev, "unable to claim gpio \"kill\"\n");
218 		return ret;
219 	}
220 
221 	data->gpio_trigger = devm_gpiod_get(&pdev->dev, "trigger",
222 					    GPIOD_IN);
223 	if (IS_ERR(ltc2952_data->gpio_trigger)) {
224 		ret = PTR_ERR(ltc2952_data->gpio_trigger);
225 		dev_err(&pdev->dev, "unable to claim gpio \"trigger\"\n");
226 		return ret;
227 	}
228 
229 	virq = gpiod_to_irq(data->gpio_trigger);
230 	if (virq < 0) {
231 		dev_err(&pdev->dev, "cannot map GPIO as interrupt");
232 		return ret;
233 	}
234 
235 	ret = devm_request_irq(&pdev->dev, virq,
236 			       ltc2952_poweroff_handler,
237 			       (IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING),
238 			       "ltc2952-poweroff",
239 			       data);
240 
241 	if (ret) {
242 		dev_err(&pdev->dev, "cannot configure an interrupt handler\n");
243 		return ret;
244 	}
245 
246 	return 0;
247 }
248 
249 static int ltc2952_poweroff_notify_panic(struct notifier_block *nb,
250 					 unsigned long code, void *unused)
251 {
252 	struct ltc2952_poweroff *data = to_ltc2952(nb, panic_notifier);
253 
254 	data->kernel_panic = true;
255 	return NOTIFY_DONE;
256 }
257 
258 static int ltc2952_poweroff_probe(struct platform_device *pdev)
259 {
260 	int ret;
261 	struct ltc2952_poweroff *data;
262 
263 	if (pm_power_off) {
264 		dev_err(&pdev->dev, "pm_power_off already registered");
265 		return -EBUSY;
266 	}
267 
268 	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
269 	if (!data)
270 		return -ENOMEM;
271 
272 	data->dev = &pdev->dev;
273 	platform_set_drvdata(pdev, data);
274 
275 	ret = ltc2952_poweroff_init(pdev);
276 	if (ret)
277 		return ret;
278 
279 	/* TODO: remove ltc2952_data */
280 	ltc2952_data = data;
281 	pm_power_off = &ltc2952_poweroff_kill;
282 
283 	data->panic_notifier.notifier_call = ltc2952_poweroff_notify_panic;
284 	atomic_notifier_chain_register(&panic_notifier_list,
285 				       &data->panic_notifier);
286 	dev_info(&pdev->dev, "probe successful\n");
287 
288 	return 0;
289 }
290 
291 static int ltc2952_poweroff_remove(struct platform_device *pdev)
292 {
293 	struct ltc2952_poweroff *data = platform_get_drvdata(pdev);
294 
295 	pm_power_off = NULL;
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("Ren� Moll <rene.moll@xsens.com>");
319 MODULE_DESCRIPTION("LTC PowerPath power-off driver");
320 MODULE_LICENSE("GPL v2");
321