Lumia 1520 mainline Linux update

Hey everyone,

It’s been a little while since my last Lumia 1520 update, so here’s where the project is at now.

The big change is that I finally have a frozen, repeatable baseline instead of just a collection of individual things that worked during testing. The current image passes 17/17 regression checks from a completely cold boot, and the exact image and device tree are now verified before I flash anything.

The Lumia currently has:

\- Reliable cold boot into mainline Linux

\- USB networking and SSH

\- Working display and backlight control

\- Stable suspend and RTC wake

\- Battery and power-management support

\- A functioning power button while the phone is awake

\- A working microSD controller, although I still need an actual card to test the media side

\- Physically verified APDS-9930 proximity and ambient-light sensors

The sensor testing was kinda cool. Covering the proximity sensor changed its reading from around 270 to 1023, and shining my phone light at the light sensor moved it from around 66 to 4830.

I also found three other devices responding on the Lumia’s I²C buses, but I’ve intentionally left them disabled for now. I documented their addresses and register behavior rather than guessing which drivers they need and potentially creating unstable hardware definitions.

The new regression suite has already paid for itself. It caught a real issue where the light/proximity sensor worked during development because I had manually loaded the driver, but it silently disappeared after a normal reboot. The physical hardware test passed, but the automated cold-boot test exposed that the driver configuration was wrong.

The next major target is audio....

The Qualcomm MSM8974 device tree currently has no SLIMbus controller node at all, even though the Linux driver exists. The plan is to add the controller, enumerate the bus, and identify the actual audio codec before assuming the Lumia uses a WCD9320. Once that is confirmed, I can begin working through the codec registers, regulators, clocks, resets, routing, speakers, microphones, and headphone output.

Power-button wake from suspend is also still unconfirmed. The key works normally while the system is awake, and RTC wake is proven, but I haven’t yet confirmed that the button can wake the phone.

The current baseline is published in the repository as commit "6b4b344", with "boot-1520.img" as the canonical image.

Repo: https://github.com/KorelisLabs/lumia-1520-mainline

Has anyone here worked with Qualcomm SLIMbus audio, WCD9320-series codecs, or audio bring-up on another MSM8974 Windows Phone?

https://redd.it/1va118o
@r_linux