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
regulator_poweroff_do_poweroff(void)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
regulator_poweroff_probe(struct platform_device * pdev)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 = ®ulator_poweroff_do_poweroff;
52 return 0;
53 }
54
regulator_poweroff_remove(__maybe_unused struct platform_device * pdev)55 static int regulator_poweroff_remove(__maybe_unused struct platform_device *pdev)
56 {
57 if (pm_power_off == ®ulator_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 MODULE_DEVICE_TABLE(of, of_regulator_poweroff_match);
68
69 static struct platform_driver regulator_poweroff_driver = {
70 .probe = regulator_poweroff_probe,
71 .remove = regulator_poweroff_remove,
72 .driver = {
73 .name = "poweroff-regulator",
74 .of_match_table = of_regulator_poweroff_match,
75 },
76 };
77
78 module_platform_driver(regulator_poweroff_driver);
79
80 MODULE_AUTHOR("Michael Klein <michael@fossekall.de>");
81 MODULE_DESCRIPTION("Regulator poweroff driver");
82 MODULE_ALIAS("platform:poweroff-regulator");
83