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