Orange Pi5 kernel

^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  1) .. SPDX-License-Identifier: GPL-2.0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  2) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  3) ============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  4) MHI Topology
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  5) ============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  6) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  7) This document provides information about the MHI topology modeling and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  8) representation in the kernel.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  9) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) MHI Controller
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) --------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) MHI controller driver manages the interaction with the MHI client devices
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) such as the external modems and WiFi chipsets. It is also the MHI bus master
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) which is in charge of managing the physical link between the host and device.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) It is however not involved in the actual data transfer as the data transfer
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) is taken care by the physical bus such as PCIe. Each controller driver exposes
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) channels and events based on the client device type.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) Below are the roles of the MHI controller driver:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) * Turns on the physical bus and establishes the link to the device
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) * Configures IRQs, IOMMU, and IOMEM
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) * Allocates struct mhi_controller and registers with the MHI bus framework
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25)   with channel and event configurations using mhi_register_controller.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) * Initiates power on and shutdown sequence
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) * Initiates suspend and resume power management operations of the device.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) MHI Device
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) ----------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) MHI device is the logical device which binds to a maximum of two MHI channels
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) for bi-directional communication. Once MHI is in powered on state, the MHI
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) core will create MHI devices based on the channel configuration exposed
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) by the controller. There can be a single MHI device for each channel or for a
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) couple of channels.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) Each supported device is enumerated in::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40)         /sys/bus/mhi/devices/
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) MHI Driver
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) ----------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) MHI driver is the client driver which binds to one or more MHI devices. The MHI
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46) driver sends and receives the upper-layer protocol packets like IP packets,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) modem control messages, and diagnostics messages over MHI. The MHI core will
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48) bind the MHI devices to the MHI driver.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50) Each supported driver is enumerated in::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52)         /sys/bus/mhi/drivers/
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) Below are the roles of the MHI driver:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56) * Registers the driver with the MHI bus framework using mhi_driver_register.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57) * Prepares the device for transfer by calling mhi_prepare_for_transfer.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58) * Initiates data transfer by calling mhi_queue_transfer.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) * Once the data transfer is finished, calls mhi_unprepare_from_transfer to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60)   end data transfer.