linux-kernel - Re: [PATCH v4 11/11] cpufreq: amd-pstate: enable shared memory type CPPC by default

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Message-ID: <4e84249b-2fa1-4d47-aa08-e8c429003714@amd.com>
Date: Tue, 18 Jun 2024 14:25:16 -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 v4 11/11] cpufreq: amd-pstate: enable shared memory type
 CPPC by default

On 6/17/2024 01:59, Perry Yuan wrote:
> The amd-pstate-epp driver has been implemented and resolves the
> performance drop issue seen in passive mode. Users who enable the
> active mode driver will not experience a performance drop compared
> to the passive mode driver. Therefore, the EPP driver should be
> loaded by default at system boot.

I think this commit message should specifically reference that it's 
being enabled by default on shared memory designs as that's the net new.

The code change looks good, go ahead and add

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

on the next version as long as you've added a sentence about shared 
memory designs to commit message.

> 
> Signed-off-by: Perry Yuan <perry.yuan@....com>
> ---
>   drivers/cpufreq/amd-pstate.c | 13 +------------
>   1 file changed, 1 insertion(+), 12 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index b48fd60cbc6d..eca2f7dcf7ce 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -96,15 +96,6 @@ enum amd_core_type {
>   	CPU_CORE_TYPE_UNDEFINED = 2,
>   };
>   
> -/*
> - * TODO: We need more time to fine tune processors with shared memory solution
> - * with community together.
> - *
> - * There are some performance drops on the CPU benchmarks which reports from
> - * Suse. We are co-working with them to fine tune the shared memory solution. So
> - * we disable it by default to go acpi-cpufreq on these processors and add a
> - * module parameter to be able to enable it manually for debugging.
> - */
>   static struct cpufreq_driver *current_pstate_driver;
>   static struct cpufreq_driver amd_pstate_driver;
>   static struct cpufreq_driver amd_pstate_epp_driver;
> @@ -1867,11 +1858,9 @@ static int __init amd_pstate_init(void)
>   		/* Disable on the following configs by default:
>   		 * 1. Undefined platforms
>   		 * 2. Server platforms
> -		 * 3. Shared memory designs
>   		 */
>   		if (amd_pstate_acpi_pm_profile_undefined() ||
> -		    amd_pstate_acpi_pm_profile_server() ||
> -		    !cpu_feature_enabled(X86_FEATURE_CPPC)) {
> +		    amd_pstate_acpi_pm_profile_server()) {
>   			pr_info("driver load is disabled, boot with specific mode to enable this\n");
>   			return -ENODEV;
>   		}