drivers/power/reset/ltc2952-poweroff.c

   1 /*
   2  * LTC2952 (PowerPath) driver
   3  *
   4  * Copyright (C) 2014, Xsens Technologies BV <info@xsens.com>
   5  * Maintainer: René 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("René Moll <rene.moll@xsens.com>");
 322 MODULE_DESCRIPTION("LTC PowerPath power-off driver");
 323 MODULE_LICENSE("GPL v2");