Introduction

Hello and Welcome to the blog on “Bubblegum96 Mainlining Update - Part 1”. This blog provides the update on the Mainlining efforts from 96Boards team for the Bubblegum96 board in Linux kernel.

Bubblegum96

Bubblegum96 board is based on Actions Semiconductor S900 64bit ARM-v8 SoC. SoC has 4 ARM Cortex-A53 cores clocked up to 1.8GHz. The clock speed itself is very unique from other A53 cores. While most of the A53 cores clocks 1.2GHz, this SoC clocks 1.8GHz. The board also has 2GB LPDDR3 RAM, 8GB on board eMMC and Power VR G6230 GPU supporting OpenGL ES 3.1, OpenGL 3.2, DirectX 10, OpenCL 1.2 EP along with other standard peripherals required by 96Boards Consumer Edition Spec.

Eventhough the SoC is powerful, the vendor support is very limited for this board. The vendor kernel is based on legacy 3.10 kernel, which is not very recent LTS kernel. For 96Boards we rely on the board/SoC manufacturer to provide the kernel support their boards. But since we get limited support from the vendor for this board, we decided to take up the upstreaming task in our spare time.

Mainlining Update

The initial board and SoC support was mainlined by Andreas Faerber from OpenSUSE. He did a great job by pushing the core platform support which is enough to boot the board into console with mainline kernel.

We then decided to join him in the upstream process and submitted the patches for the below subsystems:

  1. Clock - https://lkml.org/lkml/2018/3/26/496
  2. Pinctrl/GPIO - https://lkml.org/lkml/2018/4/4/608
  3. SPS - https://lkml.org/lkml/2018/4/11/566

As of now, both Clock and Pinctrl/GPIO subsystems are accepted by the repective subsystem maintainers and are queued up for 4.18. Still the dts patches are not yet accepted and we hope that the Actions SoC Platform maintainer Andreas will merge it when he gets time.

Conclusion

The upstreaming process has been fairly smooth with the help of the SoC datasheet and the downstream kernel. We hope to add more subsystem support in the upcoming days with our limited spare time :)