linux-kernel - Re: [PATCH 11/15] cpufreq/amd-pstate: Cache EPP value and use that everywhere

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Message-ID: <094167fa-e4c8-42cd-8d28-d6423f86f597@amd.com>
Date: Fri, 6 Dec 2024 10:16:45 -0600
From: Mario Limonciello <mario.limonciello@....com>
To: "Gautham R. Shenoy" <gautham.shenoy@....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 11/15] cpufreq/amd-pstate: Cache EPP value and use that
 everywhere

On 12/6/2024 10:14, Gautham R. Shenoy wrote:
> Hello Mario,
> 
> On Thu, Dec 05, 2024 at 04:28:43PM -0600, Mario Limonciello wrote:
>> Cache the value in cpudata->epp_cached, and use that for all callers.
>> As all callers use cached value merge amd_pstate_get_energy_pref_index()
>> into show_energy_performance_preference().
>>
>> Check if the EPP value is changed before writing it to MSR or
>> shared memory region.
> 
> The patch looks ok to me. Just one comment below:
> 
> [..snip..]
> 
>> @@ -1610,6 +1591,8 @@ static int amd_pstate_epp_set_policy(struct cpufreq_policy *policy)
>>   
>>   	cpudata->policy = policy->policy;
>>   
>> +	guard(mutex)(&amd_pstate_limits_lock);
>> +
> 
> Shouldn't this hunk be a different patch. The changelog doesn't say
> anything about making amd_pstate_epp_update_limit() call while holding
> the amd_pstate_limits_lock.

I'll drop the hunk entirely.  I'm intending an overhaul of all the mutex 
handling code after this series is landed.

> 
> 
>>   	ret = amd_pstate_epp_update_limit(policy);
>>   	if (ret)
>>   		return ret;
>> -- 
>> 2.43.0
>>
> 
> For the rest of the patch
> 
> Reviewed-by: Gautham R. Shenoy <gautham.shenoy@....com>
Thx

> 
> --
> Thanks and Regards
> gautham.