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

[Mario Limonciello <mario.limonciello@amd.com>]

On 4/10/26 04:37, Jack Wu wrote:
> [You don't often get email from wojackbb@gmail.com. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> 
> 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@compal.com>
> ---
> 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
> ---

Generally speaking this looks much better.  The only thing missing to me 
is documentation to go with it since it won't be obvious to a user what 
the "pldr" sysfs file represents.

Also in that sense - if the ACPI PALC0001 device will always represent 
WWAN reset, then maybe the sysfs file should also be called wwan_reset 
instead of pldr (platform device reset).

> ---
>   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@compal.com>
> + */
> +
> +#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
> 
>