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If something doesn't feel right let me know. > > This series addresses a boot-time performance regression on shared memory > systems where the CPU gets stuck at the lowest non-linear frequency > (1.7GHz), and adds proper EPP capability checks to prevent active mode from > being incorrectly enabled on systems without EPP support. > > Patch 1 fixes the boot-time initialization regression by introducing an > `epp_hw_programmed` flag in struct amd_cpudata to track whether EPP has > been configured on the hardware. This bypasses a false cache hit on boot > due to zero-initialized caching registers, ensuring that EPP and auto_sel > are always written during CPU initialization, while still preserving the > cache guard optimization for all subsequent runtime transitions. > > Patch 2 implements an EPP capability check at boot time using a new > amd_pstate_epp_supported() helper, which queries the EPP performance > capability on the first online CPU. If EPP is unsupported, the driver falls > back to passive mode at boot, and rejects any subsequent runtime > transitions to active mode. > > Changes in v2: > - Patch 1: Rename `epp_initialized` to `epp_hw_programmed`, explicitly > document the flag semantics, and add a comment documenting the EPP cache > guard optimization behavior. > - Patch 2: Add comments explaining the uniform CPU capability check on x86, > handle EPP capability check errors robustly using a tri-state model (only > treat -EOPNOTSUPP as unsupported, warn and assume supported for other > errors to avoid false negatives), and reject runtime active mode transitions > at sysfs store time (preventing the driver from being left in an > unregistered state). > > Changes in v1: > - Fix the boot-time CPPC EPP/auto_sel initialization regression in > shmem_set_epp() using a state tracking flag while preserving runtime > cache optimization. > - Add an EPP capability check helper during initialization. > - Fall back to passive mode at boot if EPP is not supported, and reject > transitions to active mode at runtime if EPP is not supported. > > Marco Scardovi (2): > cpufreq/amd-pstate: Fix EPP initialization for shared memory systems > cpufreq/amd-pstate: Prevent active mode on systems without EPP support > > drivers/cpufreq/amd-pstate.c | 52 +++++++++++++++++++++++++++++++++++- > drivers/cpufreq/amd-pstate.h | 2 ++ > 2 files changed, 53 insertions(+), 1 deletion(-) > Did you see Prateek's suggestion? Can you check if that helps before we go down this path? Thanks,