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

[Christian Loehle <christian.loehle@arm.com>]

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.)


>  	WRITE_ONCE(cpudata->max_freq, max_freq);
>  
>  	lowest_nonlinear_freq = perf_to_freq(perf, nominal_freq, perf.lowest_nonlinear_perf);