linux-kernel - Re: [PATCH 1/4] cpufreq/amd-pstate: Use nominal perf for limits when boost is disabled

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Message-ID: <Zw88wPX6WqCRYyRt@BLRRASHENOY1.amd.com>
Date: Wed, 16 Oct 2024 09:40:40 +0530
From: "Gautham R. Shenoy" <gautham.shenoy@....com>
To: Mario Limonciello <mario.limonciello@....com>
Cc: Perry Yuan <perry.yuan@....com>, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org,
	Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>,
	Peter Jung <ptr1337@...hyos.org>
Subject: Re: [PATCH 1/4] cpufreq/amd-pstate: Use nominal perf for limits when
 boost is disabled

Hello Mario,

On Sat, Oct 12, 2024 at 12:45:16PM -0500, Mario Limonciello wrote:
> When boost has been disabled the limit for perf should be nominal perf not
> the highest perf.  Using the latter to do calculations will lead to
> incorrect values that are still above nominal.
> 
> Fixes: ad4caad58d91 ("cpufreq: amd-pstate: Merge amd_pstate_highest_perf_set() into amd_get_boost_ratio_numerator()")
> Reported-by: Peter Jung <ptr1337@...hyos.org>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219348
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>

The patch looks good to me.

Reviewed-by: Gautham R. Shenoy <gautham.shenoy@....com>

--
Thanks and Regards
gautham.

> ---
>  drivers/cpufreq/amd-pstate.c | 20 ++++++++++++++------
>  1 file changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 30415c30d8b4..dfa9a146769b 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -536,11 +536,16 @@ static int amd_pstate_verify(struct cpufreq_policy_data *policy)
>  
>  static int amd_pstate_update_min_max_limit(struct cpufreq_policy *policy)
>  {
> -	u32 max_limit_perf, min_limit_perf, lowest_perf;
> +	u32 max_limit_perf, min_limit_perf, lowest_perf, max_perf;
>  	struct amd_cpudata *cpudata = policy->driver_data;
>  
> -	max_limit_perf = div_u64(policy->max * cpudata->highest_perf, cpudata->max_freq);
> -	min_limit_perf = div_u64(policy->min * cpudata->highest_perf, cpudata->max_freq);
> +	if (cpudata->boost_supported && !policy->boost_enabled)
> +		max_perf = READ_ONCE(cpudata->nominal_perf);
> +	else
> +		max_perf = READ_ONCE(cpudata->highest_perf);
> +
> +	max_limit_perf = div_u64(policy->max * max_perf, policy->cpuinfo.max_freq);
> +	min_limit_perf = div_u64(policy->min * max_perf, policy->cpuinfo.max_freq);


>  
>  	lowest_perf = READ_ONCE(cpudata->lowest_perf);
>  	if (min_limit_perf < lowest_perf)
> @@ -1506,10 +1511,13 @@ static int amd_pstate_epp_update_limit(struct cpufreq_policy *policy)
>  	u64 value;
>  	s16 epp;
>  
> -	max_perf = READ_ONCE(cpudata->highest_perf);
> +	if (cpudata->boost_supported && !policy->boost_enabled)
> +		max_perf = READ_ONCE(cpudata->nominal_perf);
> +	else
> +		max_perf = READ_ONCE(cpudata->highest_perf);
>  	min_perf = READ_ONCE(cpudata->lowest_perf);
> -	max_limit_perf = div_u64(policy->max * cpudata->highest_perf, cpudata->max_freq);
> -	min_limit_perf = div_u64(policy->min * cpudata->highest_perf, cpudata->max_freq);
> +	max_limit_perf = div_u64(policy->max * max_perf, policy->cpuinfo.max_freq);
> +	min_limit_perf = div_u64(policy->min * max_perf, policy->cpuinfo.max_freq);
>  
>  	if (min_limit_perf < min_perf)
>  		min_limit_perf = min_perf;
> -- 
> 2.43.0
>