[PATCH v2] platform/x86: dell-dw5826e: Add reset driver for DW5826e

[Jack Wu]

If the DW5826e is in a frozen state and unable to receive USB commands,
this driver provides a method for the user to reset the DW5826e via ACPI.

E.g: echo 1 > /sys/bus/platform/devices/PALC0001\:00/pldr

Signed-off-by: Jack Wu <jackbb_wu@xxxxxxxxxx>
---
v2:
  - Remove extra empty line
  - Add missing includes and Remove unnecessary includes, sort includes alphabetically
  - Remove noisy dev_info()
  - Handle obj->type != ACPI_TYPE_BUFFER as error with proper return code
  - Replace miscdevice/file_operations with sysfs attribute (DEVICE_ATTR_WO) to reduce boilerplate
  - Propagate trigger_palc_pldr() return code to userspace
  - Convert from acpi_driver to platform_driver
---
---
 drivers/platform/x86/dell/Kconfig             |  6 ++
 drivers/platform/x86/dell/Makefile            |  2 +
 .../platform/x86/dell/dell-dw5826e-reset.c    | 83 +++++++++++++++++++
 3 files changed, 91 insertions(+)
 create mode 100644 drivers/platform/x86/dell/dell-dw5826e-reset.c

diff --git a/drivers/platform/x86/dell/Kconfig b/drivers/platform/x86/dell/Kconfig
index 738c108c2163..c4540c837a88 100644
--- a/drivers/platform/x86/dell/Kconfig
+++ b/drivers/platform/x86/dell/Kconfig
@@ -276,4 +276,10 @@ config DELL_WMI_SYSMAN
 	  To compile this driver as a module, choose M here: the module will
 	  be called dell-wmi-sysman.
 
+config DELL_DW5826E_RESET
+	tristate "Dell DW5826e PLDR reset support"
+	default m
+	depends on ACPI
+	help
+	  This adds support for the Dell DW5826e PLDR reset via ACPI
 endif # X86_PLATFORM_DRIVERS_DELL
diff --git a/drivers/platform/x86/dell/Makefile b/drivers/platform/x86/dell/Makefile
index c7501c25e627..8150283cfd1d 100644
--- a/drivers/platform/x86/dell/Makefile
+++ b/drivers/platform/x86/dell/Makefile
@@ -28,3 +28,5 @@ obj-$(CONFIG_DELL_WMI_DESCRIPTOR)		+= dell-wmi-descriptor.o
 obj-$(CONFIG_DELL_WMI_DDV)			+= dell-wmi-ddv.o
 obj-$(CONFIG_DELL_WMI_LED)			+= dell-wmi-led.o
 obj-$(CONFIG_DELL_WMI_SYSMAN)			+= dell-wmi-sysman/
+obj-$(CONFIG_DELL_DW5826E_RESET)		+= dell-dw5826e-reset.o
+
diff --git a/drivers/platform/x86/dell/dell-dw5826e-reset.c b/drivers/platform/x86/dell/dell-dw5826e-reset.c
new file mode 100644
index 000000000000..52002578ed68
--- /dev/null
+++ b/drivers/platform/x86/dell/dell-dw5826e-reset.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  dell-dw5826e-reset.c - Dell DW5826e reset driver
+ *
+ *  Copyright (C) 2026 Jackbb Wu <jackbb.wu@xxxxxxxxxx>
+ */
+
+#include <linux/acpi.h>
+#include <linux/device.h>
+#include <linux/uuid.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+static guid_t palc_dsm_guid =
+	GUID_INIT(0x5a1a4bba, 0x8006, 0x487e, 0xbe, 0x0a, 0xac, 0xf5, 0xd8, 0xfd, 0xfe, 0x59);
+
+static int trigger_palc_pldr(struct device *dev, acpi_handle handle)
+{
+	union acpi_object *obj;
+	int ret = 0;
+
+	obj = acpi_evaluate_dsm(handle, &palc_dsm_guid, 1, 1, NULL);
+	if (!obj) {
+		dev_err(dev, "Failed to evaluate _DSM\n");
+		return -EIO;
+	}
+
+	if (obj->type != ACPI_TYPE_BUFFER) {
+		dev_err(dev, "Unexpected _DSM return type: %d\n", obj->type);
+		ret = -EINVAL;
+	}
+
+	ACPI_FREE(obj);
+	return ret;
+}
+
+static ssize_t pldr_store(struct device *dev, struct device_attribute *attr,
+			  const char *buf, size_t count)
+{
+	acpi_handle handle = ACPI_HANDLE(dev);
+	int ret;
+
+	ret = trigger_palc_pldr(dev, handle);
+	if (ret)
+		return ret;
+
+	return count;
+}
+static DEVICE_ATTR_WO(pldr);
+
+static struct attribute *palc_attrs[] = {
+	&dev_attr_pldr.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(palc);
+
+static int palc_probe(struct platform_device *pdev)
+{
+	if (!ACPI_HANDLE(&pdev->dev))
+		return -ENODEV;
+
+	return 0;
+}
+
+static const struct acpi_device_id palc_acpi_ids[] = {
+	{ "PALC0001", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(acpi, palc_acpi_ids);
+
+static struct platform_driver palc_driver = {
+	.driver = {
+		.name = "dell-dw5826e-reset",
+		.acpi_match_table = palc_acpi_ids,
+		.dev_groups = palc_groups,
+	},
+	.probe  = palc_probe,
+};
+module_platform_driver(palc_driver);
+
+MODULE_DESCRIPTION("Dell DW5826e reset driver");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("JackBB Wu");
-- 
2.34.1