linux-kernel - Re: [PATCH v3 01/18] cpufreq/amd-pstate: Invalidate cppc_req

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Message-ID: <740725e2-0580-4a52-baa1-44e722d4ce35@kernel.org>
Date: Wed, 19 Feb 2025 11:21:05 -0600
From: Mario Limonciello <superm1@...nel.org>
To: "Gautham R. Shenoy" <gautham.shenoy@....com>
Cc: Perry Yuan <perry.yuan@....com>,
 Dhananjay Ugwekar <Dhananjay.Ugwekar@....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>,
 Mario Limonciello <mario.limonciello@....com>,
 Miroslav Pavleski <miroslav@...leski.net>
Subject: Re: [PATCH v3 01/18] cpufreq/amd-pstate: Invalidate cppc_req_cached
 during suspend

On 2/18/2025 23:24, Gautham R. Shenoy wrote:
> Hello Mario,
> 
> 
> On Mon, Feb 17, 2025 at 04:06:50PM -0600, Mario Limonciello wrote:
>> From: Mario Limonciello <mario.limonciello@....com>
>>
>> During resume it's possible the firmware didn't restore the CPPC request MSR
>> but the kernel thinks the values line up. This leads to incorrect performance
>> after resume from suspend.
>>
>> To fix the issue invalidate the cached value at suspend. During resume use
>> the saved values programmed as cached limits.
>>
>> Reported-by: Miroslav Pavleski <miroslav@...leski.net>
>> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217931
>> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
>> ---
>>   drivers/cpufreq/amd-pstate.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
>> index f425fb7ec77d7..12fb63169a24c 100644
>> --- a/drivers/cpufreq/amd-pstate.c
>> +++ b/drivers/cpufreq/amd-pstate.c
>> @@ -1611,7 +1611,7 @@ static int amd_pstate_epp_reenable(struct cpufreq_policy *policy)
>>   					  max_perf, policy->boost_enabled);
>>   	}
> 
> You can also remove the tracing code from amd_pstate_epp_reenable(), i.e,
> 
> 	if (trace_amd_pstate_epp_perf_enabled()) {
> 		trace_amd_pstate_epp_perf(cpudata->cpu, cpudata->highest_perf,
> 					  cpudata->epp_cached,
> 					  FIELD_GET(AMD_CPPC_MIN_PERF_MASK, cpudata->cppc_req_cached),
> 					  max_perf, policy->boost_enabled);
> 	}
> 
> Since amd_pstate_epp_update_limit() also has the the tracing code.

Yeah; the tracing code gets updated later in the series.
My plan is this commit is a minimal fix, and will go to 6.14, the rest 
will be in 6.15.

> 
> The patch looks good to me otherwise.
> 
> Reviewed-by: Gautham R. Shenoy <gautham.shenoy@....com>
> 

Thanks!