cpufreq: amd-pstate, platform/x86/amd/hfi: Enable hybrid capacity scaling & SMT ITMT ordering on Zen 5 / Zen 5c

Hardware Observation on AMD Ryzen AI 7 350 ("Krackan Point", Family 1Ah Model 60h)
=================================================================================
On AMD Ryzen AI 7 350 (Fedora 45, Linux 7.3.3-300.fc45.x86_64 and linux-pm 7.4-rc2), the silicon interleaves 4 Classic Zen 5 physical cores (5.09 GHz max, CPUID 0x80000026 CoreType=0 / TOPO_CPU_TYPE_PERFORMANCE, ACPI CPPC prefcore_ranking 208/202/196) and 4 Dense Zen 5c physical cores (3.51 GHz max, CoreType=1 / TOPO_CPU_TYPE_EFFICIENCY, prefcore_ranking 135) inside a single 16 MiB L3 CCX:

* Even CPUs (0, 2, 4, 6; SMT 8, 10, 12, 14): Classic Zen 5 (5090.9 MHz)
* Odd CPUs (1, 3, 5, 7; SMT 9, 11, 13, 15): Dense Zen 5c (3506.5 MHz)

Observed Issues in Mainline Linux
---------------------------------
1. When X86_FEATURE_AMD_WORKLOAD_CLASS and CONFIG_AMD_HFI are enabled, amd_pstate_init_prefcore() disables amd_pstate_prefcore and delegates ITMT priorities to amd_hfi (AMDI0104:00). However, neither amd-pstate nor amd_hfi calls arch_enable_hybrid_capacity_scale(), arch_set_cpu_capacity(), or topology_set_cpu_scale(), leaving /sys/devices/system/cpu/cpu*/cpu_capacity and arch_scale_cpu_capacity() at a uniform 1024 across all 16 threads.
2. In drivers/platform/x86/amd/hfi/hfi.c, amd_set_hfi_ipcc_score() passes the class 0 IPCC score identically for primary threads and secondary SMT siblings, without distinguishing SMT secondaries via topology_sibling_cpumask().

Measured Impact on Real Silicon (Ryzen AI 7 350)
------------------------------------------------
- High-entropy 64 KiB pointer-chase + branch workload (450M instructions):

    * CPU  4 (Zen 5 Golden, CPPC 208):  66.69 ms
    * CPU 12 (Zen 5 Golden SMT)      :  66.09 ms
    * CPU  1 (Zen 5c Dense, CPPC 135):  95.18 ms (+42.7% latency penalty)

- 16-thread mixed desktop/audio contention benchmark (2 critical + 6 worker
+ 8 background cruncher threads):
* Unfenced equal-capacity placement: 75.77 ms avg | 109.22 ms worst-tail
* Hybrid core partitioning: 34.66 ms avg | 39.42 ms worst-tail

Changes in v2
-------------
- Rebased cleanly onto rafael/linux-pm.git (v7.4-rc2) and generated with git format-patch; full bzImage + modules + W=1 KCFLAGS="-Werror" build-tested and verified 0 errors, 0 warnings, 0 checks with scripts/checkpatch.pl --strict.
- Patch 1/2 (drivers/cpufreq/amd-pstate.c):
* Uses x86 arch_enable_hybrid_capacity_scale(), arch_set_cpu_capacity(), topology_set_cpu_scale(), and workqueue-deferred rebuild_sched_domains() rather than writing generic cpu_scale directly.
* Synchronizes SMT sibling capacities via topology_sibling_cpumask() so SD_SHARE_CPUCAPACITY | SD_ASYM_CPUCAPACITY warnings never trigger in kernel/sched/topology.c.
* Removes hardcoded CPU index checks and boot-order num_online_cpus() races.
- Patch 2/2 (drivers/platform/x86/amd/hfi/hfi.c):
* Scales secondary SMT sibling ITMT priorities (7/8 of primary IPCC score) via topology_sibling_cpumask() when X86_FEATURE_AMD_HTR_CORES is set.
* Removes unreferenced module-parameter stubs and raw per-CPU cpuid_count() loops.
- Updated recipient list using scripts/get_maintainer.pl.

Aiden Hecker (2):
cpufreq: amd-pstate: Enable hybrid CPU capacity scaling on
heterogeneous Zen CPUs
platform/x86/amd/hfi: Rank SMT siblings below primary cores for ITMT
packing

 drivers/cpufreq/amd-pstate.c       | 121 +++++++++++++++++++++++++++++
 drivers/platform/x86/amd/hfi/hfi.c |  18 ++++-
 2 files changed, 138 insertions(+), 1 deletion(-)

2.56.1