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X-CSE-ConnectionGUID: 6ynH0sWGTu+kBeC3WIUfhA== X-CSE-MsgGUID: ULwBZPlbRoSJvlieeYgXrw== X-IronPort-AV: E=McAfee;i="6800,10657,11759"; a="102676538" X-IronPort-AV: E=Sophos;i="6.23,179,1770624000"; d="scan'208";a="102676538" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Apr 2026 02:43:15 -0700 X-CSE-ConnectionGUID: 0C6YxCvxTA2e3bDwR/6Plw== X-CSE-MsgGUID: 38d/xnFiQhiKEKlI5oPHRg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,179,1770624000"; d="scan'208";a="227727718" Received: from ijarvine-mobl1.ger.corp.intel.com (HELO localhost) ([10.245.244.114]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Apr 2026 02:43:13 -0700 From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= Date: Wed, 15 Apr 2026 12:43:10 +0300 (EEST) To: Jack Wu cc: Hans de Goede , platform-driver-x86@vger.kernel.org, LKML Subject: Re: [PATCH v3] platform/x86: dell-dw5826e: Add reset driver for DW5826e In-Reply-To: <20260415062255.1615337-1-jackbb_wu@compal.com> Message-ID: <1b234e48-b41f-9c81-ce25-a0fe00f654d3@linux.intel.com> References: <20260415062255.1615337-1-jackbb_wu@compal.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII 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 > --- > 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 This ship has sailed long ago. ATM, you're targetting 7.2. > +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"); 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.