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61 lines
2.1 KiB
ReStructuredText
61 lines
2.1 KiB
ReStructuredText
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.. SPDX-License-Identifier: GPL-2.0
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============
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MHI Topology
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============
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This document provides information about the MHI topology modeling and
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representation in the kernel.
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MHI Controller
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--------------
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MHI controller driver manages the interaction with the MHI client devices
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such as the external modems and WiFi chipsets. It is also the MHI bus master
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which is in charge of managing the physical link between the host and device.
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It is however not involved in the actual data transfer as the data transfer
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is taken care by the physical bus such as PCIe. Each controller driver exposes
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channels and events based on the client device type.
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Below are the roles of the MHI controller driver:
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* Turns on the physical bus and establishes the link to the device
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* Configures IRQs, IOMMU, and IOMEM
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* Allocates struct mhi_controller and registers with the MHI bus framework
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with channel and event configurations using mhi_register_controller.
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* Initiates power on and shutdown sequence
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* Initiates suspend and resume power management operations of the device.
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MHI Device
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----------
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MHI device is the logical device which binds to a maximum of two MHI channels
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for bi-directional communication. Once MHI is in powered on state, the MHI
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core will create MHI devices based on the channel configuration exposed
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by the controller. There can be a single MHI device for each channel or for a
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couple of channels.
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Each supported device is enumerated in::
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/sys/bus/mhi/devices/
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MHI Driver
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----------
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MHI driver is the client driver which binds to one or more MHI devices. The MHI
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driver sends and receives the upper-layer protocol packets like IP packets,
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modem control messages, and diagnostics messages over MHI. The MHI core will
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bind the MHI devices to the MHI driver.
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Each supported driver is enumerated in::
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/sys/bus/mhi/drivers/
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Below are the roles of the MHI driver:
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* Registers the driver with the MHI bus framework using mhi_driver_register.
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* Prepares the device for transfer by calling mhi_prepare_for_transfer.
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* Initiates data transfer by calling mhi_queue_transfer.
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* Once the data transfer is finished, calls mhi_unprepare_from_transfer to
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end data transfer.
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