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         if (hrtimer_start(&data->timer_wde, data->wde_interval,
 124                           HRTIMER_MODE_REL)) {
 125                 /*
 126                  * The device will not toggle the watchdog reset,
 127                  * thus shut down is only safe if the PowerPath controller
 128                  * has a long enough time-off before triggering a hardware
 129                  * power-off.
 130                  *
 131                  * Only sending a warning as the system will power-off anyway
 132                  */
 133                 dev_err(data->dev, "unable to start the timer\n");
 134         }
 135 }
 136
 137 static enum hrtimer_restart
 138 ltc2952_poweroff_timer_trigger(struct hrtimer *timer)
 139 {
 140         struct ltc2952_poweroff *data = to_ltc2952(timer, timer_trigger);
 141
 142         ltc2952_poweroff_start_wde(data);
 143         dev_info(data->dev, "executing shutdown\n");
 144         orderly_poweroff(true);
 145
 146         return HRTIMER_NORESTART;
 147 }
 148
 149 /**
 150  * ltc2952_poweroff_handler - Interrupt handler
 151  * Triggered each time the trigger signal changes state and (de)activates a
 152  * time-out (timer_trigger). Once the time-out is actually reached the shut
 153  * down is executed.
 154  *
 155  * @irq: IRQ number
 156  * @dev_id: pointer to the main data structure
 157  */
 158 static irqreturn_t ltc2952_poweroff_handler(int irq, void *dev_id)
 159 {
 160         struct ltc2952_poweroff *data = dev_id;
 161
 162         if (data->kernel_panic || hrtimer_active(&data->timer_wde)) {
 163                 /* shutdown is already triggered, nothing to do any more */
 164                 return IRQ_HANDLED;
 165         }
 166
 167         if (gpiod_get_value(data->gpio_trigger)) {
 168                 if (hrtimer_start(&data->timer_trigger, data->trigger_delay,
 169                                   HRTIMER_MODE_REL))
 170                         dev_err(data->dev, "unable to start the wait timer\n");
 171         } else {
 172                 hrtimer_cancel(&data->timer_trigger);
 173                 /* omitting return value check, timer should have been valid */
 174         }
 175         return IRQ_HANDLED;
 176 }
 177
 178 static void ltc2952_poweroff_kill(void)
 179 {
 180         gpiod_set_value(ltc2952_data->gpio_kill, 1);
 181 }
 182
 183 static void ltc2952_poweroff_default(struct ltc2952_poweroff *data)
 184 {
 185         data->wde_interval = ktime_set(0, 300L*1E6L);
 186         data->trigger_delay = ktime_set(2, 500L*1E6L);
 187
 188         hrtimer_init(&data->timer_trigger, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 189         data->timer_trigger.function = ltc2952_poweroff_timer_trigger;
 190
 191         hrtimer_init(&data->timer_wde, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 192         data->timer_wde.function = ltc2952_poweroff_timer_wde;
 193 }
 194
 195 static int ltc2952_poweroff_init(struct platform_device *pdev)
 196 {
 197         int ret;
 198         struct ltc2952_poweroff *data = platform_get_drvdata(pdev);
 199
 200         ltc2952_poweroff_default(data);
 201
 202         data->gpio_watchdog = devm_gpiod_get(&pdev->dev, "watchdog",
 203                                              GPIOD_OUT_LOW);
 204         if (IS_ERR(data->gpio_watchdog)) {
 205                 ret = PTR_ERR(data->gpio_watchdog);
 206                 dev_err(&pdev->dev, "unable to claim gpio \"watchdog\"\n");
 207                 return ret;
 208         }
 209
 210         data->gpio_kill = devm_gpiod_get(&pdev->dev, "kill", GPIOD_OUT_LOW);
 211         if (IS_ERR(data->gpio_kill)) {
 212                 ret = PTR_ERR(data->gpio_kill);
 213                 dev_err(&pdev->dev, "unable to claim gpio \"kill\"\n");
 214                 return ret;
 215         }
 216
 217         data->gpio_trigger = devm_gpiod_get(&pdev->dev, "trigger", GPIOD_IN);
 218         if (IS_ERR(data->gpio_trigger)) {
 219                 /*
 220                  * It's not a problem if the trigger gpio isn't available, but
 221                  * it is worth a warning if its use was defined in the device
 222                  * tree.
 223                  */
 224                 if (PTR_ERR(data->gpio_trigger) != -ENOENT)
 225                         dev_err(&pdev->dev,
 226                                 "unable to claim gpio \"trigger\"\n");
 227                 data->gpio_trigger = NULL;
 228         }
 229
 230         if (devm_request_irq(&pdev->dev, gpiod_to_irq(data->gpio_trigger),
 231                              ltc2952_poweroff_handler,
 232                              (IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING),
 233                              "ltc2952-poweroff",
 234                              data)) {
 235                 /*
 236                  * Some things may have happened:
 237                  * - No trigger input was defined
 238                  * - Claiming the GPIO failed
 239                  * - We could not map to an IRQ
 240                  * - We couldn't register an interrupt handler
 241                  *
 242                  * None of these really are problems, but all of them
 243                  * disqualify the push button from controlling the power.
 244                  *
 245                  * It is therefore important to note that if the ltc2952
 246                  * detects a button press for long enough, it will still start
 247                  * its own powerdown window and cut the power on us if we don't
 248                  * start the watchdog trigger.
 249                  */
 250                 if (data->gpio_trigger) {
 251                         dev_warn(&pdev->dev,
 252                                  "unable to configure the trigger interrupt\n");
 253                         devm_gpiod_put(&pdev->dev, data->gpio_trigger);
 254                         data->gpio_trigger = NULL;
 255                 }
 256                 dev_info(&pdev->dev,
 257                          "power down trigger input will not be used\n");
 258                 ltc2952_poweroff_start_wde(data);
 259         }
 260
 261         return 0;
 262 }
 263
 264 static int ltc2952_poweroff_notify_panic(struct notifier_block *nb,
 265                                          unsigned long code, void *unused)
 266 {
 267         struct ltc2952_poweroff *data = to_ltc2952(nb, panic_notifier);
 268
 269         data->kernel_panic = true;
 270         return NOTIFY_DONE;
 271 }
 272
 273 static int ltc2952_poweroff_probe(struct platform_device *pdev)
 274 {
 275         int ret;
 276         struct ltc2952_poweroff *data;
 277
 278         if (pm_power_off) {
 279                 dev_err(&pdev->dev, "pm_power_off already registered");
 280                 return -EBUSY;
 281         }
 282
 283         data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
 284         if (!data)
 285                 return -ENOMEM;
 286
 287         data->dev = &pdev->dev;
 288         platform_set_drvdata(pdev, data);
 289
 290         ret = ltc2952_poweroff_init(pdev);
 291         if (ret)
 292                 return ret;
 293
 294         /* TODO: remove ltc2952_data */
 295         ltc2952_data = data;
 296         pm_power_off = ltc2952_poweroff_kill;
 297
 298         data->panic_notifier.notifier_call = ltc2952_poweroff_notify_panic;
 299         atomic_notifier_chain_register(&panic_notifier_list,
 300                                        &data->panic_notifier);
 301         dev_info(&pdev->dev, "probe successful\n");
 302
 303         return 0;
 304 }
 305
 306 static int ltc2952_poweroff_remove(struct platform_device *pdev)
 307 {
 308         struct ltc2952_poweroff *data = platform_get_drvdata(pdev);
 309
 310         pm_power_off = NULL;
 311         hrtimer_cancel(&data->timer_trigger);
 312         hrtimer_cancel(&data->timer_wde);
 313         atomic_notifier_chain_unregister(&panic_notifier_list,
 314                                          &data->panic_notifier);
 315         return 0;
 316 }
 317
 318 static const struct of_device_id of_ltc2952_poweroff_match[] = {
 319         { .compatible = "lltc,ltc2952"},
 320         {},
 321 };
 322 MODULE_DEVICE_TABLE(of, of_ltc2952_poweroff_match);
 323
 324 static struct platform_driver ltc2952_poweroff_driver = {
 325         .probe = ltc2952_poweroff_probe,
 326         .remove = ltc2952_poweroff_remove,
 327         .driver = {
 328                 .name = "ltc2952-poweroff",
 329                 .of_match_table = of_ltc2952_poweroff_match,
 330         },
 331 };
 332
 333 module_platform_driver(ltc2952_poweroff_driver);
 334
 335 MODULE_AUTHOR("René Moll <rene.moll@xsens.com>");
 336 MODULE_DESCRIPTION("LTC PowerPath power-off driver");
 337 MODULE_LICENSE("GPL v2");