[PATCH 0/2] x86/topology: Add support for Low Power cpu_type

[Vishal Badole]

This series extends the x86 topology cpu_type classification to support
a Low Power core type, in addition to the existing Performance and
Efficiency types.

AMD heterogeneous parts report the core type via CPUID Fn0x80000026
EBX[31:28] (Extended CPU Topology, Core Type). Value 2 identifies a
low-power core designed for minimal power consumption during background
or idle workloads. Distinguishing it from a regular efficiency core
matters for:

  - user space exposure via /sys/kernel/debug/x86/topo/cpus/*, which
    today reports cpu_type "unknown" for low-power cores

  - amd_get_boost_ratio_numerator(): on every
    X86_FEATURE_AMD_HTR_CORES-capable AMD/Hygon part, low-power cores
    must scale by amd_get_highest_perf() rather than the fixed
    CPPC_HIGHEST_PERF_PERFORMANCE ceiling, matching the existing
    efficiency-core path

The series is structured as:

  1/2 Pre-patch: replace the bare 0/1 in get_topology_cpu_type() with
      named enum amd_cpu_type constants, mirroring the existing Intel
      side. No functional change.

  2/2 Add TOPO_CPU_TYPE_LOW_POWER, wire it through
      get_topology_cpu_type(), get_topology_cpu_type_name() and the
      switch in amd_get_boost_ratio_numerator() so allmodconfig builds
      cleanly under -Werror=switch.

Vishal Badole (2):
  x86/topology: Name the AMD core-type values
  x86/topology: Add TOPO_CPU_TYPE_LOW_POWER

 arch/x86/include/asm/topology.h       | 7 +++++++
 arch/x86/kernel/acpi/cppc.c           | 3 ++-
 arch/x86/kernel/cpu/topology_common.c | 7 +++++--
 3 files changed, 14 insertions(+), 3 deletions(-)

-- 
2.34.1