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