Re: [PATCH v3] platform/x86: dell-dw5826e: Add reset driver for DW5826e

From: 吳逼逼

Date: Mon Apr 20 2026 - 02:02:26 EST

I have corrected them in version 4.

Thank you.

Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx> 於 2026年4月15日週三下午5:43寫道：
>
> On Wed, 15 Apr 2026, Jack Wu wrote:
>
>
>
> > 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
> >
> > Signed-off-by: Jack Wu <jackbb_wu@xxxxxxxxxx>
> > ---
> > 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/<PALC0001 device>/wwan_reset
> > +Date: April 2026
> > +KernelVersion: 7.0
>
> This ship has sailed long ago. ATM, you're targetting 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..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 <jackbb.wu@xxxxxxxxxx>
> > + */
> > +
> > +#include <linux/acpi.h>
> > +#include <linux/device.h>
> > +#include <linux/module.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/uuid.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");
>
> Missing include.
>
> > + 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,
>
> Please also add linux/types.h for ssize_t.
>
> > + 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");
> >
>
> --
> i.
>