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[104.199.162.7]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c70b726cbf2sm5275750a12.34.2026.02.22.09.32.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 22 Feb 2026 09:32:43 -0800 (PST) From: Kuan-Wei Chiu To: geert@linux-m68k.org, sre@kernel.org Cc: jserv@ccns.ncku.edu.tw, eleanor15x@gmail.com, daniel@0x0f.com, laurent@vivier.eu, linux-kernel@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-pm@vger.kernel.org, Kuan-Wei Chiu Subject: [PATCH v3 1/2] power: reset: Add QEMU virt-ctrl driver Date: Sun, 22 Feb 2026 17:32:24 +0000 Message-ID: <20260222173225.1105572-2-visitorckw@gmail.com> X-Mailer: git-send-email 2.53.0.345.g96ddfc5eaa-goog In-Reply-To: <20260222173225.1105572-1-visitorckw@gmail.com> References: <20260222173225.1105572-1-visitorckw@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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: Kuan-Wei Chiu --- Changes in v3: - Add a reboot notifier to handle SYS_HALT. - Implement virt_ctrl_write32() to handle native endianness. I noticed devm_register_sys_off_handler() currently lacks a SYS_OFF_MODE_HALT. Therefore, I registered a standard reboot notifier for SYS_HALT, while keeping restart and power-off on the sys-off API. MAINTAINERS | 6 ++ drivers/power/reset/Kconfig | 10 +++ drivers/power/reset/Makefile | 1 + drivers/power/reset/qemu-virt-ctrl.c | 122 +++++++++++++++++++++++++++ 4 files changed, 139 insertions(+) create mode 100644 drivers/power/reset/qemu-virt-ctrl.c diff --git a/MAINTAINERS b/MAINTAINERS index 55af015174a5..aa9eb8540637 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -21441,6 +21441,12 @@ S: Maintained F: drivers/firmware/qemu_fw_cfg.c F: include/uapi/linux/qemu_fw_cfg.h =20 +QEMU VIRT MACHINE SYSTEM CONTROLLER DRIVER +M: Kuan-Wei Chiu +L: linux-pm@vger.kernel.org +S: Maintained +F: drivers/power/reset/qemu-virt-ctrl.c + QLOGIC QL41xxx FCOE DRIVER M: Saurav Kashyap M: Javed Hasan diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig index f6c1bcbb57de..99e3334726a5 100644 --- a/drivers/power/reset/Kconfig +++ b/drivers/power/reset/Kconfig @@ -354,4 +354,14 @@ config POWER_MLXBF help This driver supports reset or low power mode handling for Mellanox Blue= Field. =20 +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 diff --git a/drivers/power/reset/Makefile b/drivers/power/reset/Makefile index 0e4ae6f6b5c5..d7ae97241a83 100644 --- a/drivers/power/reset/Makefile +++ b/drivers/power/reset/Makefile @@ -41,3 +41,4 @@ obj-$(CONFIG_SYSCON_REBOOT_MODE) +=3D syscon-reboot-mode.o obj-$(CONFIG_POWER_RESET_SC27XX) +=3D sc27xx-poweroff.o obj-$(CONFIG_NVMEM_REBOOT_MODE) +=3D nvmem-reboot-mode.o obj-$(CONFIG_POWER_MLXBF) +=3D pwr-mlxbf.o +obj-$(CONFIG_POWER_RESET_QEMU_VIRT_CTRL) +=3D qemu-virt-ctrl.o diff --git a/drivers/power/reset/qemu-virt-ctrl.c b/drivers/power/reset/qem= u-virt-ctrl.c new file mode 100644 index 000000000000..f40d04afd4e3 --- /dev/null +++ b/drivers/power/reset/qemu-virt-ctrl.c @@ -0,0 +1,122 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * QEMU Virt Machine System Controller Driver + * + * Copyright (C) 2026 Kuan-Wei Chiu + */ + +#include +#include +#include +#include +#include + +/* 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) +{ + void __iomem *base =3D data->cb_data; + + virt_ctrl_write32(CMD_HALT, base + VIRT_CTRL_REG_CMD); + + return NOTIFY_DONE; +} + +static int qemu_virt_ctrl_restart(struct sys_off_data *data) +{ + void __iomem *base =3D data->cb_data; + + virt_ctrl_write32(CMD_RESET, 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 =3D container_of(nb, struct qemu_virt_ctrl, r= eboot_nb); + + if (action =3D=3D 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 =3D devm_kzalloc(&pdev->dev, sizeof(*ctrl), GFP_KERNEL); + if (!ctrl) + return -ENOMEM; + + ctrl->base =3D devm_platform_ioremap_resource(pdev, 0); + if (IS_ERR(ctrl->base)) + return PTR_ERR(ctrl->base); + + ret =3D devm_register_sys_off_handler(&pdev->dev, + SYS_OFF_MODE_RESTART, + SYS_OFF_PRIO_DEFAULT, + qemu_virt_ctrl_restart, + ctrl->base); + if (ret) + return dev_err_probe(&pdev->dev, ret, + "cannot register restart handler\n"); + + ret =3D devm_register_sys_off_handler(&pdev->dev, + SYS_OFF_MODE_POWER_OFF, + SYS_OFF_PRIO_DEFAULT, + qemu_virt_ctrl_power_off, + ctrl->base); + if (ret) + return dev_err_probe(&pdev->dev, ret, + "cannot register power-off handler\n"); + + ctrl->reboot_nb.notifier_call =3D qemu_virt_ctrl_reboot_notify; + ret =3D 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[] =3D { + { "qemu-virt-ctrl", 0 }, + { } +}; +MODULE_DEVICE_TABLE(platform, qemu_virt_ctrl_id); + +static struct platform_driver qemu_virt_ctrl_driver =3D { + .probe =3D qemu_virt_ctrl_probe, + .driver =3D { + .name =3D "qemu-virt-ctrl", + }, + .id_table =3D qemu_virt_ctrl_id, +}; +module_platform_driver(qemu_virt_ctrl_driver); + +MODULE_AUTHOR("Kuan-Wei Chiu "); +MODULE_DESCRIPTION("QEMU Virt Machine System Controller Driver"); +MODULE_LICENSE("GPL"); --=20 2.53.0.345.g96ddfc5eaa-goog