driver: reset: th1520-aon: add driver for poweroff/reboot via AON FW

This driver implements poweroff/reboot support for T-Head TH1520 SoCs
running the AON firmware by sending a message to the AON firmware's WDG
part.

This is a auxiliary device driver, and expects the AON channel to be
passed via the platform_data of the auxiliary device.

Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
Acked-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Author: Icenowy

MAINTAINERS

@@ -21732,6 +21732,7 @@ F:	drivers/mailbox/mailbox-th1520.c
 F:	drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c
 F:	drivers/pinctrl/pinctrl-th1520.c
 F:	drivers/pmdomain/thead/
+F:	drivers/power/reset/th1520-aon-reboot.c
 F:	drivers/power/sequencing/pwrseq-thead-gpu.c
 F:	drivers/reset/reset-th1520.c
 F:	include/dt-bindings/clock/thead,th1520-clk-ap.h

drivers/power/reset/Kconfig

@@ -225,6 +225,13 @@ config POWER_RESET_ST
 	help
 	  Reset support for STMicroelectronics boards.
 
+config POWER_RESET_TH1520_AON
+	tristate "T-Head TH1520 AON firmware poweroff and reset driver"
+	depends on TH1520_PM_DOMAINS
+	help
+	  This driver supports power-off and reset operations for T-Head
+	  TH1520 SoCs running the AON firmware.
+
 config POWER_RESET_TORADEX_EC
 	tristate "Toradex Embedded Controller power-off and reset driver"
 	depends on ARCH_MXC || COMPILE_TEST

drivers/power/reset/Makefile

@@ -25,6 +25,7 @@ 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-$(CONFIG_POWER_RESET_TH1520_AON) += th1520-aon-reboot.o
 obj-$(CONFIG_POWER_RESET_TORADEX_EC) += tdx-ec-poweroff.o
 obj-$(CONFIG_POWER_RESET_TPS65086) += tps65086-restart.o
 obj-$(CONFIG_POWER_RESET_VERSATILE) += arm-versatile-reboot.o

drivers/power/reset/th1520-aon-reboot.c

@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * T-HEAD TH1520 AON Firmware Reboot Driver
+ *
+ * Copyright (c) 2025 Icenowy Zheng <uwu@icenowy.me>
+ */
+
+#include <linux/auxiliary_bus.h>
+#include <linux/firmware/thead/thead,th1520-aon.h>
+#include <linux/module.h>
+#include <linux/notifier.h>
+#include <linux/of.h>
+#include <linux/reboot.h>
+#include <linux/slab.h>
+
+#define TH1520_AON_REBOOT_PRIORITY 200
+
+struct th1520_aon_msg_empty_body {
+	struct th1520_aon_rpc_msg_hdr hdr;
+	u16 reserved[12];
+} __packed __aligned(1);
+
+static int th1520_aon_pwroff_handler(struct sys_off_data *data)
+{
+	struct th1520_aon_chan *aon_chan = data->cb_data;
+	struct th1520_aon_msg_empty_body msg = {};
+
+	msg.hdr.svc = TH1520_AON_RPC_SVC_WDG;
+	msg.hdr.func = TH1520_AON_WDG_FUNC_POWER_OFF;
+	msg.hdr.size = TH1520_AON_RPC_MSG_NUM;
+
+	th1520_aon_call_rpc(aon_chan, &msg);
+
+	return NOTIFY_DONE;
+}
+
+static int th1520_aon_restart_handler(struct sys_off_data *data)
+{
+	struct th1520_aon_chan *aon_chan = data->cb_data;
+	struct th1520_aon_msg_empty_body msg = {};
+
+	msg.hdr.svc = TH1520_AON_RPC_SVC_WDG;
+	msg.hdr.func = TH1520_AON_WDG_FUNC_RESTART;
+	msg.hdr.size = TH1520_AON_RPC_MSG_NUM;
+
+	th1520_aon_call_rpc(aon_chan, &msg);
+
+	return NOTIFY_DONE;
+}
+
+static int th1520_aon_reboot_probe(struct auxiliary_device *adev,
+				  const struct auxiliary_device_id *id)
+{
+	struct device *dev = &adev->dev;
+	int ret;
+
+	/* Expect struct th1520_aon_chan to be passed via platform_data */
+	ret = devm_register_sys_off_handler(dev, SYS_OFF_MODE_POWER_OFF,
+					    TH1520_AON_REBOOT_PRIORITY,
+					    th1520_aon_pwroff_handler,
+					    adev->dev.platform_data);
+
+	if (ret) {
+		dev_err(dev, "Failed to register power off handler\n");
+		return ret;
+	}
+
+	ret = devm_register_sys_off_handler(dev, SYS_OFF_MODE_RESTART,
+					    TH1520_AON_REBOOT_PRIORITY,
+					    th1520_aon_restart_handler,
+					    adev->dev.platform_data);
+
+	if (ret) {
+		dev_err(dev, "Failed to register restart handler\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct auxiliary_device_id th1520_aon_reboot_id_table[] = {
+	{ .name = "th1520_pm_domains.reboot" },
+	{},
+};
+MODULE_DEVICE_TABLE(auxiliary, th1520_aon_reboot_id_table);
+
+static struct auxiliary_driver th1520_aon_reboot_driver = {
+	.driver = {
+		.name = "th1520-aon-reboot",
+	},
+	.probe = th1520_aon_reboot_probe,
+	.id_table = th1520_aon_reboot_id_table,
+};
+module_auxiliary_driver(th1520_aon_reboot_driver);
+
+MODULE_AUTHOR("Icenowy Zheng <uwu@icenowy.me>");
+MODULE_DESCRIPTION("T-HEAD TH1520 AON-firmware-based reboot driver");
+MODULE_LICENSE("GPL");