[PATCH v7 1/2] platform/x86: dell-dw5826e: Add reset driver for DW5826e
From: Jack Wu
Date: Mon May 25 2026 - 03:02:17 EST
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/wwan_reset
Reviewed-by: Mario Limonciello (AMD) <superm1@xxxxxxxxxx>
Reviewed-by: Armin Wolf <W_Armin@xxxxxx>
Signed-off-by: Jack Wu <jackbb_wu@xxxxxxxxxx>
---
v7:
- Place BIT() into PALC_DSM_FN_TRIGGER_PLDR define
v6:
- Use same define for the DSM check
v5:
- Use BIT() for the DSM method
v4:
- Fix version of the ABI documentation to 7.2
- Add include linux/types.h
v3:
- Rename sysfs attribute from "pldr" to "wwan_reset" for clarity
- Add ABI documentation for the wwan_reset sysfs interface
- Validate _DSM method availability in probe using acpi_check_dsm()
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
---
---
.../testing/sysfs-driver-dell-dw5826e-reset | 9 ++
drivers/platform/x86/dell/Kconfig | 6 ++
drivers/platform/x86/dell/Makefile | 2 +
.../platform/x86/dell/dell-dw5826e-reset.c | 93 +++++++++++++++++++
4 files changed, 110 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-driver-dell-dw5826e-reset
create mode 100644 drivers/platform/x86/dell/dell-dw5826e-reset.c
diff --git a/Documentation/ABI/testing/sysfs-driver-dell-dw5826e-reset b/Documentation/ABI/testing/sysfs-driver-dell-dw5826e-reset
new file mode 100644
index 000000000000..a665e265633f
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-dell-dw5826e-reset
@@ -0,0 +1,9 @@
+What: /sys/bus/platform/devices/<PALC0001 device>/wwan_reset
+Date: April 2026
+KernelVersion: 7.2
+Contact: Jackbb Wu <jackbb.wu@xxxxxxxxxx>
+Description:
+ Writing to this file triggers a Platform Level Device Reset
+ (PLDR) of the Dell DW5826e WWAN module via an ACPI _DSM
+ method. This can be used to recover the modem when it is in
+ a frozen state and unable to respond to USB commands.
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..1ca7c3421bb5
--- /dev/null
+++ b/drivers/platform/x86/dell/dell-dw5826e-reset.c
@@ -0,0 +1,93 @@
+// 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/bits.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+#include <linux/uuid.h>
+
+#define PALC_DSM_FN_TRIGGER_PLDR BIT(1)
+
+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, PALC_DSM_FN_TRIGGER_PLDR, 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 wwan_reset_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(wwan_reset);
+
+static struct attribute *palc_attrs[] = {
+ &dev_attr_wwan_reset.attr,
+ NULL
+};
+ATTRIBUTE_GROUPS(palc);
+
+static int palc_probe(struct platform_device *pdev)
+{
+ acpi_handle handle;
+
+ handle = ACPI_HANDLE(&pdev->dev);
+ if (!handle)
+ return -ENODEV;
+
+ if (!acpi_check_dsm(handle, &palc_dsm_guid, 1, PALC_DSM_FN_TRIGGER_PLDR))
+ 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
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