linux-kernel - Re: [PATCH 07/15] cpufreq/amd-pstate: Only update the cached value in msr_set

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Message-ID: <Z1Kaj7zUiYcgCGUj@BLRRASHENOY1.amd.com>
Date: Fri, 6 Dec 2024 12:02:47 +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>
Subject: Re: [PATCH 07/15] cpufreq/amd-pstate: Only update the cached value
 in msr_set_epp() on success

On Thu, Dec 05, 2024 at 04:28:39PM -0600, Mario Limonciello wrote:
> If writing the MSR MSR_AMD_CPPC_REQ fails then the cached value in the
> amd_cpudata structure should not be updated.

Considering that the remote MSR update can fail only if either the
cpudata->cpu is invalid or if that CPU is not online, this is the
right thing to do.

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

--
Thanks and Regards
gautham.



> 
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
>  drivers/cpufreq/amd-pstate.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 14bd6faa3d730..ce70d1bfa55d0 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -278,11 +278,15 @@ static int msr_set_epp(struct amd_cpudata *cpudata, u32 epp)
>  
>  	value &= ~AMD_PSTATE_EPP_PERF_MASK;
>  	value |= FIELD_PREP(AMD_PSTATE_EPP_PERF_MASK, epp);
> -	WRITE_ONCE(cpudata->cppc_req_cached, value);
>  
>  	ret = wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
> -	if (!ret)
> -		cpudata->epp_cached = epp;
> +	if (ret) {
> +		pr_err("failed to set energy perf value (%d)\n", ret);
> +		return ret;
> +	}
> +
> +	cpudata->epp_cached = epp;
> +	WRITE_ONCE(cpudata->cppc_req_cached, value);
>  
>  	return ret;
>  }
> -- 
> 2.43.0
>