linux-kernel - Re: [PATCH] cpufreq/amd-pstate: Fix a regression leading to EPP 0 after resume

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Message-ID: <aLhZKNnnyUXOX5wk@BLRRASHENOY1.amd.com>
Date: Wed, 3 Sep 2025 20:35:12 +0530
From: "Gautham R. Shenoy" <gautham.shenoy@....com>
To: "Mario Limonciello (AMD)" <superm1@...nel.org>
Cc: Perry Yuan <perry.yuan@....com>,
	"open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <linux-kernel@...r.kernel.org>,
	"open list:CPU FREQUENCY SCALING FRAMEWORK" <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] cpufreq/amd-pstate: Fix a regression leading to EPP 0
 after resume

Hello Mario,


On Tue, Aug 26, 2025 at 12:27:47AM -0500, Mario Limonciello (AMD) wrote:
> During the suspend sequence the cached CPPC request is destroyed
> with the expectation that it's restored during resume.  This assumption
> broke when the separate cache EPP variable was removed, and then it was
> broken again by commit 608a76b65288 ("cpufreq/amd-pstate: Add support
> for the "Requested CPU Min frequency" BIOS option") which explicitly
> set it to zero during suspend.
> 
> Remove the invalidation and set the value during the suspend call to
> update limits so that the cached variable can be used to restore on
> resume.
> 
> Fixes: 608a76b65288 ("cpufreq/amd-pstate: Add support for the "Requested CPU Min frequency" BIOS option")
> Fixes: b7a41156588a ("cpufreq/amd-pstate: Invalidate cppc_req_cached during suspend")
> Closes: https://community.frame.work/t/increased-power-usage-after-resuming-from-suspend-on-ryzen-7040-kernel-6-15-regression/
> Signed-off-by: Mario Limonciello (AMD) <superm1@...nel.org>
> ---
>  drivers/cpufreq/amd-pstate.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index bbc27ef9edf7b..8eca4707226b8 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -1626,13 +1626,14 @@ static int amd_pstate_suspend(struct cpufreq_policy *policy)
>  	 * min_perf value across kexec reboots. If this CPU is just resumed back without kexec,
>  	 * the limits, epp and desired perf will get reset to the cached values in cpudata struct
>  	 */
> -	ret = amd_pstate_update_perf(policy, perf.bios_min_perf, 0U, 0U, 0U, false);
> +	ret = amd_pstate_update_perf(policy, perf.bios_min_perf,
> +				     FIELD_GET(AMD_CPPC_DES_PERF_MASK, cpudata->cppc_req_cached),
> +				     FIELD_GET(AMD_CPPC_MAX_PERF_MASK, cpudata->cppc_req_cached),
> +				     FIELD_GET(AMD_CPPC_EPP_PERF_MASK, cpudata->cppc_req_cached),
> +				     false);
>  	if (ret)
>  		return ret;
>  
> -	/* invalidate to ensure it's rewritten during resume */
> -	cpudata->cppc_req_cached = 0;
> -

Ah, so cppc_req_cached is required to extract the EPP value in
amd_pstate_epp_update_limit() which is called by
amd_pstate_epp_resume().

Looks good to me.

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

-- 
Thanks and Regards
gautham.



>  	/* set this flag to avoid setting core offline*/
>  	cpudata->suspended = true;
>  
> -- 
> 2.43.0
>