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Some Surface Book 2 and 3 models have a discrete GPU (dGPU) that is hot-pluggable. On those devices, the dGPU is contained in the base, which can be separated from the tablet part (containing CPU and touchscreen) while the device is running. It (in general) is presented as/behaves like a standard PCIe hot-plug capable device, however, this device can also be put into D3cold. In D3cold, the device itself is turned off and can thus not submit any standard PCIe hot-plug events. To properly detect hot-(un)plugging while the dGPU is in D3cold, out-of-band signaling is required. Without this, the device state will only get updated during the next bus-check, eg. via a manually issued lspci call. This commit adds a driver to handle out-of-band PCIe hot-(un)plug events on Microsoft Surface devices. On those devices, said events can be detected via GPIO interrupts, which are then forwarded to the corresponding ACPI DSM calls by this driver. The DSM then takes care of issuing the appropriate bus-/device-check, causing the PCI core to properly pick up the device change. Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com> Link: https://lore.kernel.org/r/20210205012657.1951753-1-luzmaximilian@gmail.com Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.