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Message-ID: <20260112182258.1851769-2-visitorckw@gmail.com>
Date: Mon, 12 Jan 2026 18:22:56 +0000
From: Kuan-Wei Chiu <visitorckw@...il.com>
To: geert@...ux-m68k.org,
sre@...nel.org
Cc: jserv@...s.ncku.edu.tw,
eleanor15x@...il.com,
linux-kernel@...r.kernel.org,
linux-m68k@...ts.linux-m68k.org,
linux-pm@...r.kernel.org,
Kuan-Wei Chiu <visitorckw@...il.com>
Subject: [PATCH 1/2] 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 registers a restart handler for system reboot and sets the
global pm_power_off callback for system shutdown. 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 <visitorckw@...il.com>
---
MAINTAINERS | 6 ++
drivers/power/reset/Kconfig | 10 +++
drivers/power/reset/Makefile | 1 +
drivers/power/reset/qemu-virt-ctrl.c | 98 ++++++++++++++++++++++++++++
4 files changed, 115 insertions(+)
create mode 100644 drivers/power/reset/qemu-virt-ctrl.c
diff --git a/MAINTAINERS b/MAINTAINERS
index 0d044a58cbfe..2586e4162304 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -21179,6 +21179,12 @@ 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@...il.com>
+L: linux-pm@...r.kernel.org
+S: Maintained
+F: drivers/power/reset/qemu-virt-ctrl.c
+
QLOGIC QL41xxx FCOE DRIVER
M: Saurav Kashyap <skashyap@...vell.com>
M: Javed Hasan <jhasan@...vell.com>
diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
index f6c1bcbb57de..1ca1c2913cbc 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 BlueField.
+config POWER_RESET_QEMU_VIRT_CTRL
+ bool "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-$(CONFIG_SYSCON_REBOOT_MODE) += syscon-reboot-mode.o
obj-$(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
diff --git a/drivers/power/reset/qemu-virt-ctrl.c b/drivers/power/reset/qemu-virt-ctrl.c
new file mode 100644
index 000000000000..f1acd22172ce
--- /dev/null
+++ b/drivers/power/reset/qemu-virt-ctrl.c
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * QEMU Virt Machine System Controller Driver
+ *
+ * Copyright (C) 2026 Kuan-Wei Chiu <visitorckw@...il.com>
+ */
+
+#include <linux/io.h>
+#include <linux/module.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 restart_nb;
+};
+
+static void __iomem *qemu_virt_ctrl_base;
+
+static void qemu_virt_ctrl_power_off(void)
+{
+ if (qemu_virt_ctrl_base)
+ iowrite32be(CMD_HALT, qemu_virt_ctrl_base + VIRT_CTRL_REG_CMD);
+}
+
+static int qemu_virt_ctrl_restart(struct notifier_block *nb, unsigned long action,
+ void *data)
+{
+ struct qemu_virt_ctrl *vc = container_of(nb, struct qemu_virt_ctrl, restart_nb);
+
+ iowrite32be(CMD_RESET, vc->base + VIRT_CTRL_REG_CMD);
+
+ return NOTIFY_DONE;
+}
+
+static int qemu_virt_ctrl_probe(struct platform_device *pdev)
+{
+ struct qemu_virt_ctrl *vc;
+ int ret;
+
+ vc = devm_kzalloc(&pdev->dev, sizeof(*vc), GFP_KERNEL);
+ if (!vc)
+ return -ENOMEM;
+
+ vc->base = devm_platform_ioremap_resource(pdev, 0);
+ if (IS_ERR(vc->base))
+ return PTR_ERR(vc->base);
+
+ qemu_virt_ctrl_base = vc->base;
+
+ vc->restart_nb.notifier_call = qemu_virt_ctrl_restart;
+ vc->restart_nb.priority = 128;
+
+ ret = register_restart_handler(&vc->restart_nb);
+ if (ret)
+ return dev_err_probe(&pdev->dev, ret,
+ "cannot register restart handler\n");
+
+ if (!pm_power_off)
+ pm_power_off = qemu_virt_ctrl_power_off;
+
+ platform_set_drvdata(pdev, vc);
+
+ return 0;
+}
+
+static void qemu_virt_ctrl_remove(struct platform_device *pdev)
+{
+ struct qemu_virt_ctrl *vc = platform_get_drvdata(pdev);
+
+ unregister_restart_handler(&vc->restart_nb);
+
+ if (pm_power_off == qemu_virt_ctrl_power_off)
+ pm_power_off = NULL;
+}
+
+static struct platform_driver qemu_virt_ctrl_driver = {
+ .probe = qemu_virt_ctrl_probe,
+ .remove = qemu_virt_ctrl_remove,
+ .driver = {
+ .name = "qemu-virt-ctrl",
+ },
+};
+module_platform_driver(qemu_virt_ctrl_driver);
+
+MODULE_AUTHOR("Kuan-Wei Chiu <visitorckw@...il.com>");
+MODULE_DESCRIPTION("QEMU Virt Machine System Controller Driver");
+MODULE_LICENSE("GPL");
--
2.52.0.457.g6b5491de43-goog
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