C-SKY 32-Bit CPUs Aim For Initial Support In Linux 4.20~5.0
At the start of the year is when the Linux kernel port to C-SKY was posted while now it's hoping to be mainlined for this next kernel cycle. C-SKY is a Chinese 32-bit CPU architecture for embedded 32-bit SoCs. These SoCs are low-power and intended for use-cases like cameras, set-top TV/media boxes, digital video recorders, printers, and other consumer appliances as well as industrial devices.
C-SKY Microsystems has joined the RISC-V Foundation but this current architecture doesn't appear based on RISC-V at all. In addition to the kernel bring-up, this year they have also volleyed patches for porting GCC to C-SKY along with other open-source user-space toolchain work for this new architecture.
The prominent C-SKY CPU core at this point appears to be the CK801 and supports 16/32-bit variable length instructions, only relies upon 70+ core instructions, and has a 2-stage pipeline.
Sent out this Saturday morning was a pull request seeking the inclusion of this "csky" kernel port to be added for Linux 4.20~5.0. The port has already gone through ten rounds of public code review over the past number of months and the port adds over 11,000 lines of code for bringing up the new architecture.
As of writing this port hasn't yet been merged so we'll see if Linus Torvalds decides it's ready for integration or will have to hold off for another cycle.
Until the rest of the C-SKY open-source support gets upstreamed, the company has made available their patches via GitHub against Glibc, U-Boot, uClibc, GCC, QEMU, and Binutils.
C-SKY is just one of several homegrown Chinese CPU efforts happening at the moment. Linux 4.20 is also bringing support for the AMD Zen-based Hygon Dhyana SoCs while there is also the VIA-partnered Zhaoxin CPUs that already have Linux support. Additionally there is also the long-standing MIPS-based Loongson processors that have long been supported.