driver: reset: spacemit-p1: add driver for poweroff/reboot

This driver implements poweroff/reboot support for the SpacemiT P1 PMIC
chip, which is commonly paired with the SpacemiT K1 SoC.

The SpacemiT P1 support is implemented as a MFD driver, so the access is
done directly through the regmap interface. Reboot or poweroff is
triggered by setting a specific bit in a control register, which is
automatically cleared by the hardware afterwards.

Signed-off-by: Aurelien Jarno <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Sebastian Reichel <[e-mail]>

drivers/power/reset/Kconfig

···
 	help
 	  Reboot support for the KEYSTONE SoCs.
 
+config POWER_RESET_SPACEMIT_P1
+	tristate "SpacemiT P1 poweroff and reset driver"
+	depends on ARCH_SPACEMIT || COMPILE_TEST
+	depends on MFD_SPACEMIT_P1
+	default MFD_SPACEMIT_P1
+	help
+	  This driver supports power-off and reset operations for the SpacemiT
+	  P1 PMIC.
+
 config POWER_RESET_SYSCON
 	bool "Generic SYSCON regmap reset driver"
 	depends on OF

drivers/power/reset/Makefile

···
 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_SPACEMIT_P1) += spacemit-p1-reboot.o
 obj-$(CONFIG_POWER_RESET_ST) += st-poweroff.o
 obj-$(CONFIG_POWER_RESET_TH1520_AON) += th1520-aon-reboot.o
 obj-$(CONFIG_POWER_RESET_TORADEX_EC) += tdx-ec-poweroff.o

drivers/power/reset/spacemit-p1-reboot.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2025 by Aurelien Jarno
+ */
+
+#include <linux/bits.h>
+#include <linux/mod_devicetable.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/reboot.h>
+
+/* Power Control Register 2 */
+#define PWR_CTRL2		0x7e
+#define PWR_CTRL2_SHUTDOWN	BIT(2)	/* Shutdown request */
+#define PWR_CTRL2_RST		BIT(1)	/* Reset request */
+
+static int spacemit_p1_pwroff_handler(struct sys_off_data *data)
+{
+	struct regmap *regmap = data->cb_data;
+	int ret;
+
+	/* Put the PMIC into shutdown state */
+	ret = regmap_set_bits(regmap, PWR_CTRL2, PWR_CTRL2_SHUTDOWN);
+	if (ret) {
+		dev_err(data->dev, "shutdown failed: %d\n", ret);
+		return notifier_from_errno(ret);
+	}
+
+	return NOTIFY_DONE;
+}
+
+static int spacemit_p1_restart_handler(struct sys_off_data *data)
+{
+	struct regmap *regmap = data->cb_data;
+	int ret;
+
+	/* Put the PMIC into reset state */
+	ret = regmap_set_bits(regmap, PWR_CTRL2, PWR_CTRL2_RST);
+	if (ret) {
+		dev_err(data->dev, "restart failed: %d\n", ret);
+		return notifier_from_errno(ret);
+	}
+
+	return NOTIFY_DONE;
+}
+
+static int spacemit_p1_reboot_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct regmap *regmap;
+	int ret;
+
+	regmap = dev_get_regmap(dev->parent, NULL);
+	if (!regmap)
+		return -ENODEV;
+
+	ret = devm_register_power_off_handler(dev, &spacemit_p1_pwroff_handler,
+					      regmap);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "Failed to register power off handler\n");
+
+	ret = devm_register_restart_handler(dev, spacemit_p1_restart_handler,
+					    regmap);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "Failed to register restart handler\n");
+
+	return 0;
+}
+
+static const struct platform_device_id spacemit_p1_reboot_id_table[] = {
+	{ "spacemit-p1-reboot", },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(platform, spacemit_p1_reboot_id_table);
+
+static struct platform_driver spacemit_p1_reboot_driver = {
+	.driver = {
+		.name = "spacemit-p1-reboot",
+	},
+	.probe = spacemit_p1_reboot_probe,
+	.id_table = spacemit_p1_reboot_id_table,
+};
+module_platform_driver(spacemit_p1_reboot_driver);
+
+MODULE_DESCRIPTION("SpacemiT P1 reboot/poweroff driver");
+MODULE_LICENSE("GPL");