[PATCH v5 1/3] power: reset: new driver regulator-poweroff

[Michael Klein]

This driver registers a pm_power_off function to turn off the board
by force-disabling a devicetree-defined regulator.

Signed-off-by: Michael Klein <michael at fossekall.de>
---
 drivers/power/reset/Kconfig              |  7 ++
 drivers/power/reset/Makefile             |  1 +
 drivers/power/reset/regulator-poweroff.c | 82 ++++++++++++++++++++++++
 3 files changed, 90 insertions(+)
 create mode 100644 drivers/power/reset/regulator-poweroff.c

diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
index d55b3727e00e..b22c4fdb2561 100644
--- a/drivers/power/reset/Kconfig
+++ b/drivers/power/reset/Kconfig
@@ -177,6 +177,13 @@ config POWER_RESET_QNAP
 
 	  Say Y if you have a QNAP NAS.
 
+config POWER_RESET_REGULATOR
+	bool "Regulator subsystem power-off driver"
+	depends on OF && REGULATOR
+	help
+	  This driver supports turning off your board by disabling a
+	  power regulator defined in the devicetree.
+
 config POWER_RESET_RESTART
 	bool "Restart power-off driver"
 	help
diff --git a/drivers/power/reset/Makefile b/drivers/power/reset/Makefile
index c51eceba9ea3..9dc49d3a57ff 100644
--- a/drivers/power/reset/Makefile
+++ b/drivers/power/reset/Makefile
@@ -19,6 +19,7 @@ obj-$(CONFIG_POWER_RESET_OCELOT_RESET) += ocelot-reset.o
 obj-$(CONFIG_POWER_RESET_PIIX4_POWEROFF) += piix4-poweroff.o
 obj-$(CONFIG_POWER_RESET_LTC2952) += ltc2952-poweroff.o
 obj-$(CONFIG_POWER_RESET_QNAP) += qnap-poweroff.o
+obj-$(CONFIG_POWER_RESET_REGULATOR) += regulator-poweroff.o
 obj-$(CONFIG_POWER_RESET_RESTART) += restart-poweroff.o
 obj-$(CONFIG_POWER_RESET_ST) += st-poweroff.o
 obj-$(CONFIG_POWER_RESET_VERSATILE) += arm-versatile-reboot.o
diff --git a/drivers/power/reset/regulator-poweroff.c b/drivers/power/reset/regulator-poweroff.c
new file mode 100644
index 000000000000..f697088e0ad1
--- /dev/null
+++ b/drivers/power/reset/regulator-poweroff.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Force-disables a regulator to power down a device
+ *
+ * Michael Klein <michael at fossekall.de>
+ *
+ * Copyright (C) 2020 Michael Klein
+ *
+ * Based on the gpio-poweroff driver.
+ */
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pm.h>
+#include <linux/regulator/consumer.h>
+
+#define TIMEOUT_MS 3000
+
+/*
+ * Hold configuration here, cannot be more than one instance of the driver
+ * since pm_power_off itself is global.
+ */
+static struct regulator *cpu_regulator;
+
+static void regulator_poweroff_do_poweroff(void)
+{
+	if (cpu_regulator && regulator_is_enabled(cpu_regulator))
+		regulator_force_disable(cpu_regulator);
+
+	/* give it some time */
+	mdelay(TIMEOUT_MS);
+
+	WARN_ON(1);
+}
+
+static int regulator_poweroff_probe(struct platform_device *pdev)
+{
+	/* If a pm_power_off function has already been added, leave it alone */
+	if (pm_power_off != NULL) {
+		dev_err(&pdev->dev,
+			"%s: pm_power_off function already registered\n",
+			__func__);
+		return -EBUSY;
+	}
+
+	cpu_regulator = devm_regulator_get(&pdev->dev, "cpu");
+	if (IS_ERR(cpu_regulator))
+		return PTR_ERR(cpu_regulator);
+
+	pm_power_off = &regulator_poweroff_do_poweroff;
+	return 0;
+}
+
+static int regulator_poweroff_remove(__maybe_unused struct platform_device *pdev)
+{
+	if (pm_power_off == &regulator_poweroff_do_poweroff)
+		pm_power_off = NULL;
+
+	return 0;
+}
+
+static const struct of_device_id of_regulator_poweroff_match[] = {
+	{ .compatible = "regulator-poweroff", },
+	{},
+};
+
+static struct platform_driver regulator_poweroff_driver = {
+	.probe = regulator_poweroff_probe,
+	.remove = regulator_poweroff_remove,
+	.driver = {
+		.name = "poweroff-regulator",
+		.of_match_table = of_regulator_poweroff_match,
+	},
+};
+
+module_platform_driver(regulator_poweroff_driver);
+
+MODULE_AUTHOR("Michael Klein <michael at fossekall.de>");
+MODULE_DESCRIPTION("Regulator poweroff driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:poweroff-regulator");
-- 
2.29.2