Kernel 5.4 MHI backport

This repo contains backports of the drivers for the MHI bus, the MHI network interface driver and the new wwan framwork. MHI is required driver for (among others) for using SDX55-based modems (like Quectel RM500Q or Telit FN980) together with PCI. Please note that the steps for enable PCI between each modem, and that you hardware (m.2 slot) has to support PCI (often in addition to USB).

The repo is structured as follows:

• drivers/bus/mhi: Code for the MHI bus.
• drivers/net: Network interface driver and wwan framework.
• include/linux: MHI/wwan framework header files.
• patches/kernel: Kernel patches. For the individual commits, please refer to the repos I have based my backport on (linux-next and net-next).
• patches/openwrt: Contains a patch adding OpenWrt packages for the different drivers/framework.

I will try to keep this repo reasonably up to date, but PRs are more than welcome. The drivers are tested and works fine on kernel 5.4.144. When testing, I used Quectel RM502Q-AE modem, and was able to communicate with the module and establish a data connection (using qmicli) + send and receive data.

List of changes

The backport is made up of the following changes:

MHI

• Based on linux-next 999569d59a0aa2509ae4a67ecc266c1134e37e7b.
• Copied the driver/bus/mhi directory.
• Added include/linux/mhi.h.
• MHI-related changes driver/bus/Kconfig, drivers/bus/Makefile and include/linux/mod_devicetable.h.
• Backported fsleep to delay.h.

mhi_net

• Based on net-next 626bf91a292e2035af5b9d9cce35c5c138dfe06d.
• Added the MHI network driver.
• Replace u64_stats_t + functions with u64 and regular increment operations. u64_stats_t does not exist in kernel 5.4.

wwan framework

• Based on net-next 626bf91a292e2035af5b9d9cce35c5c138dfe06d.
• Copied the drivers/net/wwan directory.
• Replaced u64_stats_t.
• Backport two rtnetlink-changes required by the wwan framework (separate patches).