LoongArch Wires Up Real-Time Kernel Support & Lazy Preemption

Merged for the Linux 6.12 kernel was the long-awaited real-time "PREEMPT_RT" kernel support and allowing it to be enabled across x86/x86_64, ARM64, and RISC-V CPU architectures. With the Linux 6.13 kernel, LoongArch is joining the RT party.

All of the LoongArch architecture updates were sent out overnight for the ongoing Linux 6.13 kernel merge window. Notable this cycle is allowing to build LoongArck kernels with PREEMPT_RT support enabled for those wanting real-time support on this Chinese CPU architecture.

In addition to PREEMPT_RT support, LoongArch also is introducing PREEMPT_LAZY support. This lazy preemption mode is new to Linux 6.13 and LoongArch is ready to go with allowing it to be supported too.

Other LoongArch changes for Linux 6.13 include addressing a build failure using the in-development GCC 15 compiler, I2S support being enabled in the DTS file for the Loongson-2K1000/Loongson-2K2000, and other small changes. More details within this pull request.