Introduction to OpenPOWER Firmware¶
The op-build project constructs a host firmware image for OpenPOWER
machines.
Firmware Components¶
- Buildroot
- We use http://buildroot.net/ as the build system for assembling a firmware image. op-build is a “Buildroot overlay”. We build a kernel and initramfs using buildroot to run the Petitboot boot loader in. We maintain a branch with a minimum number of patches on top of upstream buildroot.
- op-build
- A buildroot overlay that assembles OpenPOWER Firmware images.
- SBE
- the Self Boot Engine is the first unit inside the POWER processor to start executing. It’s job is to set up a core and load Hostboot.
- Hostboot
- Low level system boot firmware. It brings up CPU cores, the OCC, Memory and hands control over to OPAL (skiboot)
- OCC
- The On Chip Controller is responsible for thermal limits and frequency management.
- OPAL
- The OpenPOWER Abstraction Layer, provided by skiboot
- skiboot
- skiboot implements OPAL (the OpenPOWER Abstraction Layer). Skiboot is boot and runtime firmware and is responsible for bringing up PCI and providing runtime abstractions to the running OS.
- Linux
- Once skiboot has finished setting up the machine, it hands control over to a Linux kernel. This kernel provides device drivers and userspace to run the bootloader, Petitboot. We maintain our own branch with a minimal number of patches on top of the latest upstream stable release.
- Petitboot
- The bootloader. It is a normal user-space process running on Linux that searches the system for disks and network devices that it can boot the OS from.
- HCODE
- Firmware for the power management PPE. Implements heavy lifting for deeper STOP states.
Introductory Videos¶
There are a number of good recorded presentations from various conferences around the world that have overviews and deep dives into various parts of the firmware stack.
Here, we present technical presentations that may be useful in learning about topics relevant to OpenPOWER firmware development.
For broader OpenPOWER topics, check out the following channels:
- OpenPOWER Foundation <https://github.com/open-power/op-build/pull/2983>`_