linux-kernel - Re: [PATCH v8 4/6] cpufreq: amd-pstate: fix the MSR highest perf will be reset issue while cpb boost off

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Date: Fri, 26 Apr 2024 09:11:15 -0500
From: Mario Limonciello <mario.limonciello@....com>
To: Perry Yuan <perry.yuan@....com>, rafael.j.wysocki@...el.com,
 viresh.kumar@...aro.org, Ray.Huang@....com, gautham.shenoy@....com,
 Borislav.Petkov@....com
Cc: Alexander.Deucher@....com, Xinmei.Huang@....com, Xiaojian.Du@....com,
 Li.Meng@....com, linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 4/6] cpufreq: amd-pstate: fix the MSR highest perf will
 be reset issue while cpb boost off

On 4/26/2024 01:34, Perry Yuan wrote:
> From: Perry Yuan <Perry.Yuan@....com>
> 
> Select the min perf to fix the highest perf value while update pstate
> CPPC request MSR register, here we need to limit the max perf value when
don't use we in a commit message
> CPU boost is disabled in case of that highest perf value in the MSR will be
> reset to original highest perf value which cause the BOOST control
> failed.
> 
> Signed-off-by: Perry Yuan <Perry.Yuan@....com>
> Acked-by: Huang Rui <ray.huang@....com>

With minor nit fixed in commit message.

Reviewed-by: Mario Limonciello <mario.limonciello@....com>

> ---
>   drivers/cpufreq/amd-pstate.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 53ef39c6dbfa..993e3e6b6609 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -476,6 +476,7 @@ static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf,
>   			      u32 des_perf, u32 max_perf, bool fast_switch, int gov_flags)
>   {
>   	u64 prev = READ_ONCE(cpudata->cppc_req_cached);
> +	u32 nominal_perf = READ_ONCE(cpudata->nominal_perf);
>   	u64 value = prev;
>   
>   	min_perf = clamp_t(unsigned long, min_perf, cpudata->min_limit_perf,
> @@ -495,6 +496,10 @@ static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf,
>   	value &= ~AMD_CPPC_DES_PERF(~0L);
>   	value |= AMD_CPPC_DES_PERF(des_perf);
>   
> +	/* limit the max perf when core performance boost feature is disabled */
> +	if (!amd_pstate_global_params.cpb_boost)
> +		max_perf = min_t(unsigned long, nominal_perf, max_perf);
> +
>   	value &= ~AMD_CPPC_MAX_PERF(~0L);
>   	value |= AMD_CPPC_MAX_PERF(max_perf);
>