drivers/power/reset/regulator-poweroff.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Force-disables a regulator to power down a device
   4  *
   5  * Michael Klein <michael@fossekall.de>
   6  *
   7  * Copyright (C) 2020 Michael Klein
   8  *
   9  * Based on the gpio-poweroff driver.
  10  */
  11 #include <linux/delay.h>
  12 #include <linux/module.h>
  13 #include <linux/of.h>
  14 #include <linux/platform_device.h>
  15 #include <linux/pm.h>
  16 #include <linux/regulator/consumer.h>
  17
  18 #define TIMEOUT_MS 3000
  19
  20 /*
  21  * Hold configuration here, cannot be more than one instance of the driver
  22  * since pm_power_off itself is global.
  23  */
  24 static struct regulator *cpu_regulator;
  25
  26 static void regulator_poweroff_do_poweroff(void)
  27 {
  28         if (cpu_regulator && regulator_is_enabled(cpu_regulator))
  29                 regulator_force_disable(cpu_regulator);
  30
  31         /* give it some time */
  32         mdelay(TIMEOUT_MS);
  33
  34         WARN_ON(1);
  35 }
  36
  37 static int regulator_poweroff_probe(struct platform_device *pdev)
  38 {
  39         /* If a pm_power_off function has already been added, leave it alone */
  40         if (pm_power_off != NULL) {
  41                 dev_err(&pdev->dev,
  42                         "%s: pm_power_off function already registered\n",
  43                         __func__);
  44                 return -EBUSY;
  45         }
  46
  47         cpu_regulator = devm_regulator_get(&pdev->dev, "cpu");
  48         if (IS_ERR(cpu_regulator))
  49                 return PTR_ERR(cpu_regulator);
  50
  51         pm_power_off = &regulator_poweroff_do_poweroff;
  52         return 0;
  53 }
  54
  55 static int regulator_poweroff_remove(__maybe_unused struct platform_device *pdev)
  56 {
  57         if (pm_power_off == &regulator_poweroff_do_poweroff)
  58                 pm_power_off = NULL;
  59
  60         return 0;
  61 }
  62
  63 static const struct of_device_id of_regulator_poweroff_match[] = {
  64         { .compatible = "regulator-poweroff", },
  65         {},
  66 };
  67
  68 static struct platform_driver regulator_poweroff_driver = {
  69         .probe = regulator_poweroff_probe,
  70         .remove = regulator_poweroff_remove,
  71         .driver = {
  72                 .name = "poweroff-regulator",
  73                 .of_match_table = of_regulator_poweroff_match,
  74         },
  75 };
  76
  77 module_platform_driver(regulator_poweroff_driver);
  78
  79 MODULE_AUTHOR("Michael Klein <michael@fossekall.de>");
  80 MODULE_DESCRIPTION("Regulator poweroff driver");
  81 MODULE_LICENSE("GPL v2");
  82 MODULE_ALIAS("platform:poweroff-regulator");