Re: [PATCH v3 3/3] cpufreq/amd-pstate: Get Highest Freq for a CPU

[Mario Limonciello <superm1@kernel.org>]

On 10/1/26 05:03, Christian Loehle wrote:
> On 9/24/26 17:00, Mario Limonciello (AMD) wrote:
>> From: Mario Limonciello <mario.limonciello@amd.com>
>>
>> If the highest frequency is known for a CPU, use this instead of
>> trying to calculate by linear interpolation.
>>
>> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
>> ---
>>   drivers/cpufreq/amd-pstate.c | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
>> index 496e0342c1c90..2a0cbfe21a67d 100644
>> --- a/drivers/cpufreq/amd-pstate.c
>> +++ b/drivers/cpufreq/amd-pstate.c
>> @@ -1102,8 +1102,10 @@ static int amd_pstate_init_freq(struct amd_cpudata *cpudata)
>>   
>>   	WRITE_ONCE(cpudata->nominal_freq, nominal_freq);
>>   
>> -	/* max_freq is calculated according to (nominal_freq * highest_perf)/nominal_perf */
>> -	max_freq = perf_to_freq(perf, nominal_freq, perf.highest_perf);
>> +	/* try to look up from BIOS/quirk first, fall back to (nominal_freq * highest_perf)/nominal_perf */
>> +	max_freq = amd_get_max_frequency(cpudata->cpu) * 1000;
>> +	if (!max_freq)
>> +		max_freq = perf_to_freq(perf, nominal_freq, perf.highest_perf);
> 
> Don't you need to align freq_to_perf() (or the callers) for the BIOS-overwrite case too?
> amd_pstate_update_min_max_limit() still uses the nominal-based conversion for policy->max,
> so the new maximum frequency maps back to highest_perf on each core type?
> (and we end up with max_limit_perf < highest_perf if the BIOS-overwrite values are below
> the interpolation result.)
> 
> 
That's an excellent finding, thanks.