Commit ad9d2cd0 authored by Kuan-Wei Chiu's avatar Kuan-Wei Chiu Committed by Geert Uytterhoeven
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power: reset: Add QEMU virt-ctrl driver 

Add a new driver for the 'virt-ctrl' device found on QEMU virt machines
(e.g. m68k). This device provides a simple interface for system reset
and power off [1].

This driver utilizes the modern system-off API to register callbacks
for both system restart and power off. It also registers a reboot
notifier to catch SYS_HALT events, ensuring that LINUX_REBOOT_CMD_HALT
is properly handled. It is designed to be generic and can be reused by
other architectures utilizing this QEMU device.

Link: https://gitlab.com/qemu-project/qemu/-/blob/v10.2.0/hw/misc/virt_ctrl.c

 [1]
Signed-off-by: default avatarKuan-Wei Chiu <visitorckw@gmail.com>
Acked-by: default avatarSebastian Reichel <sebastian.reichel@collabora.com>
Link: https://patch.msgid.link/20260412211952.3564033-2-visitorckw@gmail.com


Signed-off-by: default avatarGeert Uytterhoeven <geert@linux-m68k.org>
parent cbd3b8ef

MAINTAINERS

+6 −0
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@@ -21441,6 +21441,12 @@ S: Maintained 
F:	drivers/firmware/qemu_fw_cfg.c

F:	include/uapi/linux/qemu_fw_cfg.h









QEMU VIRT MACHINE SYSTEM CONTROLLER DRIVER









M:	Kuan-Wei Chiu <visitorckw@gmail.com>









L:	linux-pm@vger.kernel.org









S:	Maintained









F:	drivers/power/reset/qemu-virt-ctrl.c

















QLOGIC QL41xxx FCOE DRIVER









M:	Saurav Kashyap <skashyap@marvell.com>









M:	Javed Hasan <jhasan@marvell.com>

























drivers/power/reset/Kconfig



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−0






























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@@ -354,4 +354,14 @@ config POWER_MLXBF







	help









	  This driver supports reset or low power mode handling for Mellanox BlueField.



















config POWER_RESET_QEMU_VIRT_CTRL









	tristate "QEMU Virt Machine System Controller"









	depends on HAS_IOMEM









	help









	  This driver supports the system reset and power off functionality









	  provided by the QEMU 'virt-ctrl' device.



















	  Say Y here if you are running Linux on a QEMU virtual machine that









	  provides this controller, such as the m68k virt machine.



















endif
























drivers/power/reset/Makefile



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@@ -41,3 +41,4 @@ obj-$(CONFIG_SYSCON_REBOOT_MODE) += syscon-reboot-mode.o







obj-$(CONFIG_POWER_RESET_SC27XX) += sc27xx-poweroff.o









obj-$(CONFIG_NVMEM_REBOOT_MODE) += nvmem-reboot-mode.o









obj-$(CONFIG_POWER_MLXBF) += pwr-mlxbf.o









obj-$(CONFIG_POWER_RESET_QEMU_VIRT_CTRL) += qemu-virt-ctrl.o
























drivers/power/reset/qemu-virt-ctrl.c
0 → 100644



+122
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// SPDX-License-Identifier: GPL-2.0









/*









 * QEMU Virt Machine System Controller Driver









 *









 * Copyright (C) 2026 Kuan-Wei Chiu <visitorckw@gmail.com>









 */



















#include <linux/io.h>









#include <linux/module.h>









#include <linux/mod_devicetable.h>









#include <linux/platform_device.h>









#include <linux/reboot.h>



















/* Registers */









#define VIRT_CTRL_REG_FEATURES	0x00









#define VIRT_CTRL_REG_CMD	0x04



















/* Commands */









#define CMD_NOOP	0









#define CMD_RESET	1









#define CMD_HALT	2









#define CMD_PANIC	3



















struct qemu_virt_ctrl {









	void __iomem *base;









	struct notifier_block reboot_nb;









};



















static inline void virt_ctrl_write32(u32 val, void __iomem *addr)









{









	if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))









		iowrite32be(val, addr);









	else









		iowrite32(val, addr);









}



















static int qemu_virt_ctrl_power_off(struct sys_off_data *data)









{









	struct qemu_virt_ctrl *ctrl = data->cb_data;



















	virt_ctrl_write32(CMD_HALT, ctrl->base + VIRT_CTRL_REG_CMD);



















	return NOTIFY_DONE;









}



















static int qemu_virt_ctrl_restart(struct sys_off_data *data)









{









	struct qemu_virt_ctrl *ctrl = data->cb_data;



















	virt_ctrl_write32(CMD_RESET, ctrl->base + VIRT_CTRL_REG_CMD);



















	return NOTIFY_DONE;









}



















static int qemu_virt_ctrl_reboot_notify(struct notifier_block *nb,









					unsigned long action, void *data)









{









	struct qemu_virt_ctrl *ctrl = container_of(nb, struct qemu_virt_ctrl, reboot_nb);



















	if (action == SYS_HALT)









		virt_ctrl_write32(CMD_HALT, ctrl->base + VIRT_CTRL_REG_CMD);



















	return NOTIFY_DONE;









}



















static int qemu_virt_ctrl_probe(struct platform_device *pdev)









{









	struct qemu_virt_ctrl *ctrl;









	int ret;



















	ctrl = devm_kzalloc(&pdev->dev, sizeof(*ctrl), GFP_KERNEL);









	if (!ctrl)









		return -ENOMEM;



















	ctrl->base = devm_platform_ioremap_resource(pdev, 0);









	if (IS_ERR(ctrl->base))









		return PTR_ERR(ctrl->base);



















	ret = devm_register_sys_off_handler(&pdev->dev,









					    SYS_OFF_MODE_RESTART,









					    SYS_OFF_PRIO_DEFAULT,









					    qemu_virt_ctrl_restart,









					    ctrl);









	if (ret)









		return dev_err_probe(&pdev->dev, ret,









				     "cannot register restart handler\n");



















	ret = devm_register_sys_off_handler(&pdev->dev,









					    SYS_OFF_MODE_POWER_OFF,









					    SYS_OFF_PRIO_DEFAULT,









					    qemu_virt_ctrl_power_off,









					    ctrl);









	if (ret)









		return dev_err_probe(&pdev->dev, ret,









				     "cannot register power-off handler\n");



















	ctrl->reboot_nb.notifier_call = qemu_virt_ctrl_reboot_notify;









	ret = devm_register_reboot_notifier(&pdev->dev, &ctrl->reboot_nb);









	if (ret)









		return dev_err_probe(&pdev->dev, ret, "cannot register reboot notifier\n");



















	return 0;









}



















static const struct platform_device_id qemu_virt_ctrl_id[] = {









	{ "qemu-virt-ctrl", 0 },









	{ }









};









MODULE_DEVICE_TABLE(platform, qemu_virt_ctrl_id);



















static struct platform_driver qemu_virt_ctrl_driver = {









	.probe = qemu_virt_ctrl_probe,









	.driver = {









		.name = "qemu-virt-ctrl",









	},









	.id_table = qemu_virt_ctrl_id,









};









module_platform_driver(qemu_virt_ctrl_driver);



















MODULE_AUTHOR("Kuan-Wei Chiu <visitorckw@gmail.com>");









MODULE_DESCRIPTION("QEMU Virt Machine System Controller Driver");









MODULE_LICENSE("GPL");