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The Surface ACPI Notify (SAN) device provides an ACPI interface to the Surface Aggregator EC, specifically the Surface Serial Hub interface. This interface allows EC requests to be made from ACPI code and can convert a subset of EC events back to ACPI notifications. Specifically, this interface provides a GenericSerialBus operation region ACPI code can execute a request by writing the request command data and payload to this operation region and reading back the corresponding response via a write-then-read operation. Furthermore, this interface provides a _DSM method to be called when certain events from the EC have been received, essentially turning them into ACPI notifications. The driver provided in this commit essentially takes care of translating the request data written to the operation region, executing the request, waiting for it to finish, and finally writing and translating back the response (if the request has one). Furthermore, this driver takes care of enabling the events handled via ACPI _DSM calls. Lastly, this driver also exposes an interface providing discrete GPU (dGPU) power-on notifications on the Surface Book 2, which are also received via the operation region interface (but not handled by the SAN driver directly), making them accessible to other drivers (such as a dGPU hot-plug driver that may be added later on). On 5th and 6th generation Surface devices (Surface Pro 5/2017, Pro 6, Book 2, Laptop 1 and 2), the SAN interface provides full battery and thermal subsystem access, as well as other EC based functionality. On those models, battery and thermal sensor devices are implemented as standard ACPI devices of that type, however, forward ACPI calls to the corresponding Surface Aggregator EC request via the SAN interface and receive corresponding notifications (e.g. battery information change) from it. This interface is therefore required to provide said functionality on those devices. Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com> Reviewed-by: Hans de Goede <hdegoede@redhat.com> Link: https://lore.kernel.org/r/20201221183959.1186143-10-luzmaximilian@gmail.com Signed-off-by: Hans de Goede <hdegoede@redhat.com>
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1.8 KiB
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44 lines
1.8 KiB
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.. SPDX-License-Identifier: GPL-2.0+
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.. |san_client_link| replace:: :c:func:`san_client_link`
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.. |san_dgpu_notifier_register| replace:: :c:func:`san_dgpu_notifier_register`
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.. |san_dgpu_notifier_unregister| replace:: :c:func:`san_dgpu_notifier_unregister`
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===================
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Surface ACPI Notify
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===================
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The Surface ACPI Notify (SAN) device provides the bridge between ACPI and
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SAM controller. Specifically, ACPI code can execute requests and handle
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battery and thermal events via this interface. In addition to this, events
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relating to the discrete GPU (dGPU) of the Surface Book 2 can be sent from
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ACPI code (note: the Surface Book 3 uses a different method for this). The
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only currently known event sent via this interface is a dGPU power-on
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notification. While this driver handles the former part internally, it only
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relays the dGPU events to any other driver interested via its public API and
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does not handle them.
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The public interface of this driver is split into two parts: Client
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registration and notifier-block registration.
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A client to the SAN interface can be linked as consumer to the SAN device
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via |san_client_link|. This can be used to ensure that the a client
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receiving dGPU events does not miss any events due to the SAN interface not
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being set up as this forces the client driver to unbind once the SAN driver
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is unbound.
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Notifier-blocks can be registered by any device for as long as the module is
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loaded, regardless of being linked as client or not. Registration is done
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with |san_dgpu_notifier_register|. If the notifier is not needed any more, it
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should be unregistered via |san_dgpu_notifier_unregister|.
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Consult the API documentation below for more details.
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API Documentation
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=================
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.. kernel-doc:: include/linux/surface_acpi_notify.h
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.. kernel-doc:: drivers/platform/surface/surface_acpi_notify.c
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:export:
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