MIPS Preparing Many Changes For Linux 4.21

The MIPS CPU architecture has suddenly become a bit more interesting now that the processor ISA will be open-sourced in 2019. With the in-development Linux 4.21 kernel there are a number of MIPS support changes inbound.

The upstream Linux kernel code for MIPS continues to be improved, particularly for their newer efforts. Some of the highlights for Linux 4.21 include:

- Support for building the MIPS Linux kernel without floating point support. This effort is about shrinking the kernel and preparing for nanoMIPS that currently offers no floating-point capabilities. The nanoMIPS architecture is designed to have around 40% smaller code size than MIPS32 and also being very power efficient.

- The entire MIPS kernel can now be built with the Undefined Behavior Sanitizer enabled. Also, the kernel can be built with the link-time dead code and data elimination passes enabled.

- Cleanup to the Cavium Octeon code that resulted in around 20k lines of code reduction.

- Continued work on the Loongson 3 support. The MIPS64 Loongson 3 is/was popular in some circles but is showing its age these days with being manufactured on a 65nm process (or 32nm on the Loongson 3B) and sporting just ~1GHz clock speeds and a few cores, not to mention being hard to find.

- Various optimizations and other low-level improvements.

More details on the MIPS code changes for Linux 4.21 can be found via this pull request.

Do you have much hope for MIPS in 2019 now that they are opening up their ISA? Let us know your thoughts in the forums.