linux-kernel - Re: [PATCH v12 7/9] cpufreq: amd-pstate: fix the MSR highest perf will be reset issue while cpb boost off

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Date: Fri, 21 Jun 2024 11:16:24 +0530
From: Gautham R.Shenoy <gautham.shenoy@....com>
To: Perry Yuan <perry.yuan@....com>, <rafael.j.wysocki@...el.com>,
	<Mario.Limonciello@....com>, <viresh.kumar@...aro.org>
CC: <Xinmei.Huang@....com>, <Xiaojian.Du@....com>, <Li.Meng@....com>,
	<linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v12 7/9] cpufreq: amd-pstate: fix the MSR highest perf
 will be reset issue while cpb boost off

Perry Yuan <perry.yuan@....com> writes:

> From: Perry Yuan <Perry.Yuan@....com>
>
> Select the min perf to fix the highest perf value while update pstate
> CPPC request MSR register, here it needs to limit the max perf value when
> 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.

Perhaps we could rephrase this as

"When Core Performance Boost is disabled by the user, the
CPPC_REQ.max_perf should not exceed the nominal_perf since by definition
the frequencies between nominal_perf and the highest_perf are in the
boost range. Fix this in amd_pstate_update()"

Also change the subject to

"cpufreq:amd-pstate: Cap the CPPC.max_perf to nominal_perf if CPB is off"

?
>
> Signed-off-by: Perry Yuan <Perry.Yuan@....com>
> Acked-by: Huang Rui <ray.huang@....com>
> Reviewed-by: Mario Limonciello <mario.limonciello@....com>

Other than that,

Reviewed-by: Gautham R. Shenoy <gautham.shenoy@....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 299e52d4b17e..f2ccef089acc 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -524,6 +524,7 @@ 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,
> @@ -543,6 +544,10 @@ 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);
>  
> -- 
> 2.34.1

--
Thanks and Regards
gautham.