platform/x86: dell-dw5826e: Add reset driver for DW5826e

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) <superm1@kernel.org>
Reviewed-by: Armin Wolf <W_Armin@gmx.de>
Signed-off-by: Jack Wu <jackbb_wu@compal.com>
Link: https://patch.msgid.link/20260526-dell-reset-v8-v8-1-d3a29cb4cf2f@compal.com
[ij: removed default m]
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

diff --git a/Documentation/ABI/testing/sysfs-driver-dell-dw5826e-reset b/Documentation/ABI/testing/sysfs-driver-dell-dw5826e-reset
new file mode 100644 (file)
index 0000000..a665e26
--- /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: 7.2
+Contact:       Jackbb Wu <jackbb.wu@compal.com>
+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 738c108c2163eeeac1354603f1deda4b4dc7d426..9f0016056d7e6230acdb22a4ca7eee615bd8f107 100644 (file)
--- a/drivers/platform/x86/dell/Kconfig
+++ b/drivers/platform/x86/dell/Kconfig
@@ -276,4 +276,9 @@ 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"
+       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 c7501c25e627504f621ee5be15635c919d448823..470874c6e6e6abd64569eaa7f88c08bb364705cc 100644 (file)
--- a/drivers/platform/x86/dell/Makefile
+++ b/drivers/platform/x86/dell/Makefile
@@ -28,3 +28,4 @@ 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 (file)
index 0000000..1ca7c34
--- /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 <jackbb.wu@compal.com>
+ */
+
+#include <linux/acpi.h>
+#include <linux/bits.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+#include <linux/uuid.h>
+
+#define PALC_DSM_FN_TRIGGER_PLDR    BIT(1)
+
+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, PALC_DSM_FN_TRIGGER_PLDR, 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, PALC_DSM_FN_TRIGGER_PLDR))
+               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");