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E.g: echo 1 > /sys/bus/platform/devices/PALC0001\:00/wwan_reset Signed-off-by: Jack Wu --- 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 | 89 +++++++++++++++++++ 4 files changed, 106 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..88286191caa6 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-driver-dell-dw5826e-reset @@ -0,0 +1,9 @@ +What: /sys/bus/platform/devices//wwan_reset +Date: April 2026 +KernelVersion: 7.0 +Contact: Jackbb Wu +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..98c5b68c8746 --- /dev/null +++ b/drivers/platform/x86/dell/dell-dw5826e-reset.c @@ -0,0 +1,89 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * dell-dw5826e-reset.c - Dell DW5826e reset driver + * + * Copyright (C) 2026 Jackbb Wu + */ + +#include +#include +#include +#include +#include + +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 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, BIT(1))) + 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