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X-CSE-ConnectionGUID: trjrkNE3Q4iU8qcHFG0iwg== X-CSE-MsgGUID: tLWvioy3R9OO0dETOcp90w== X-IronPort-AV: E=McAfee;i="6800,10657,11771"; a="78423127" X-IronPort-AV: E=Sophos;i="6.23,208,1770624000"; d="scan'208";a="78423127" Received: from fmviesa001.fm.intel.com ([10.60.135.141]) by orvoesa111.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Apr 2026 05:38:35 -0700 X-CSE-ConnectionGUID: FK3+kHw6R2SqHfo/9Kxfvw== X-CSE-MsgGUID: WzH8TF7jRIWoW40aOOsUaw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,208,1770624000"; d="scan'208";a="258149971" Received: from ijarvine-mobl1.ger.corp.intel.com (HELO localhost) ([10.245.244.130]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Apr 2026 05:38:31 -0700 From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= Date: Thu, 30 Apr 2026 15:38:28 +0300 (EEST) To: Jack Wu cc: Hans de Goede , platform-driver-x86@vger.kernel.org, LKML , Mario Limonciello , Armin Wolf Subject: Re: [PATCH v5] platform/x86: dell-dw5826e: Add reset driver for DW5826e In-Reply-To: <20260429060643.2367630-1-jackbb_wu@compal.com> Message-ID: References: <20260429060643.2367630-1-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, 29 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 > > Reviewed-by: Mario Limonciello (AMD) > Reviewed-by: Armin Wolf > Signed-off-by: Jack Wu > --- > 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//wwan_reset > +Date: April 2026 > +KernelVersion: 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..24b18062ae0e > --- /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 > + */ > + > +#include > +#include > +#include > +#include > +#include > +#include > +#include > + > +#define PALC_DSM_FN_TRIGGER_PLDR 1 > + > +static guid_t palc_dsm_guid = This can be const. > + 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, BIT(PALC_DSM_FN_TRIGGER_PLDR), NULL); Should the BIT() be part of the define? -- i. > + 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"); >