linux-kernel - Re: [PATCH 2/2] cpufreq/amd-pstate: Fix the scaling_min/max_freq setting on shared memory CPPC systems

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Date: Wed, 26 Jun 2024 13:40:37 +0530
From: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
To: Mario Limonciello <mario.limonciello@....com>
Cc: linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
 "Rafael J. Wysocki" <rafael@...nel.org>,
 Viresh Kumar <viresh.kumar@...aro.org>,
 Shuah Khan <skhan@...uxfoundation.org>, Huang Rui <ray.huang@....com>,
 Perry Yuan <Perry.Yuan@....com>, Meng Li <li.meng@....com>,
 "Gautham R. Shenoy" <gautham.shenoy@....com>
Subject: Re: [PATCH 2/2] cpufreq/amd-pstate: Fix the scaling_min/max_freq
 setting on shared memory CPPC systems

Hello Mario,

On 6/25/2024 8:39 PM, Mario Limonciello wrote:
> On 6/25/2024 08:41, Dhananjay Ugwekar wrote:
>> On shared memory CPPC systems, with amd_pstate=active mode, the change
>> in scaling_min/max_freq doesn't get written to the shared memory
>> region. Due to this, the writes to the scaling_min/max_freq sysfs file
>> don't take effect. Fix this by propagating the scaling_min/max_freq
>> changes to the shared memory region.
>>
>> Fixes: ffa5096a7c33 ("cpufreq: amd-pstate: implement Pstate EPP support for the AMD processors")
>> Signed-off-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
>> ---
>>   drivers/cpufreq/amd-pstate.c | 10 ++++++++++
>>   1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
>> index 9ad62dbe8bfb..7c1c96abe5bd 100644
>> --- a/drivers/cpufreq/amd-pstate.c
>> +++ b/drivers/cpufreq/amd-pstate.c
>> @@ -264,6 +264,15 @@ static int amd_pstate_set_epp(struct amd_cpudata *cpudata, u32 epp)
>>               cpudata->epp_cached = epp;
>>       } else {
>>           perf_ctrls.energy_perf = epp;
>> +        perf_ctrls.max_perf = cpudata->max_limit_perf;
>> +        perf_ctrls.min_perf = cpudata->min_limit_perf;
>> +        perf_ctrls.desired_perf = 0U;
>> +
>> +        ret = cppc_set_perf(cpudata->cpu, &perf_ctrls);
>> +        if (ret) {
>> +            pr_debug("failed to set min max limits (%d)\n", ret);
>> +            return ret;
>> +        }
> 
> This feels like a handgrown implementation of amd_pstate_update_perf() (IE static call updated to cppc_update_perf).

Yes, I didn't notice it, better to call the existing function.

> 
> Can you just call that instead?
> 
>>           ret = cppc_set_epp_perf(cpudata->cpu, &perf_ctrls, 1);
>>           if (ret) {
>>               pr_debug("failed to set energy perf value (%d)\n", ret);
>> @@ -1547,6 +1556,7 @@ static void amd_pstate_epp_update_limit(struct cpufreq_policy *policy)
>>       }
>>         WRITE_ONCE(cpudata->cppc_req_cached, value);
>> +
> 
> Spurious newline added here not relevant to this patch.

Yes, will remove it

Regards,
Dhananjay

>>       amd_pstate_set_epp(cpudata, epp);
>>   }
>>   
>