[PATCH v2 0/2] cpufreq: CPPC: Rework FIE warning prints and cppc_scale_freq_tick()

[Jie Zhan]

Hi All,

I'm still looking forward to some feedback or tests on this series.

Cheers,
Jie

On 9/16/2025 10:58 AM, Jie Zhan wrote:
> A kindly ping on this.
> Some feedback would be nice if anyone is not on holiday ;)
> 
> Jie
> 
> On 8/28/2025 7:02 PM, Jie Zhan wrote:
>> Reading performance feedback counters on offline or low-power idle CPUs may
>> return 0, which is interpreted as -EFAULT.
>>
>> This leads to two issues related to the CPPC FIE:
>>
>> 1. When booting a subset of CPUs in policy->related_cpus (some CPUs under
>> the cpufreq policy is offline), there are warnings of "failed to read perf
>> counters for cpu" during the CPPC FIE initialization.
>>
>> 2. On our platform with the CPC regs in System Memory and a power-down idle
>> state enabled, if the CPPC FIE is registered successfully, there are
>> repeated warnings of "failed to read perf counters" because
>> cppc_scale_freq_workfn() is trying to access the counters of remote CPUs
>> that enters the idle state.
>>
>> To solve the above issues:
>>
>> Patch 1 removes the warning when the CPPC FIE initialization fails to read
>> counters on offline CPUs and changes the log leve to debug.  This can be
>> applied separately.
>>
>> Patch 2 moves the update of FIE arch_freq_scale into ticks for non-PCC regs
>> and maintains the existing mechanism for PCC regs, such that reading
>> counters would be triggered on the local CPU only.  This inherently solves
>> the issue in [1].  We have tested this on Kunpeng SoCs with the CPC regs
>> both in System Memory and FFH.  More tests on other platforms are welcome
>> though.
>> [1] https://lore.kernel.org/linux-pm/20250730032312.167062-3-yubowen8@huawei.com/
>>
>> Changelog:
>>
>> v2:
>> - Update the cover letter and the commit log based on v1 discussion
>> - Update FIE arch_freq_scale in ticks for non-PCC regs
>>
>> v1:
>> https://lore.kernel.org/linux-pm/20250730032312.167062-1-yubowen8@huawei.com/
>>
>> Jie Zhan (2):
>>   cpufreq: CPPC: Don't warn if FIE init fails to read counters
>>   cpufreq: CPPC: Update FIE arch_freq_scale in ticks for non-PCC regs
>>
>>  drivers/cpufreq/cppc_cpufreq.c | 64 +++++++++++++++++++++-------------
>>  1 file changed, 39 insertions(+), 25 deletions(-)
>>