Re: [PATCH v3 10/15] cpufreq/amd-pstate: Move limit updating code

[Mario Limonciello <mario.limonciello@amd.com>]

On 12/16/2024 08:16, Dhananjay Ugwekar wrote:
> Hello Mario,
> 
> On 12/10/2024 12:22 AM, Mario Limonciello wrote:
>> The limit updating code in amd_pstate_epp_update_limit() should not
>> only apply to EPP updates.  Move it to amd_pstate_update_min_max_limit()
>> so other callers can benefit as well.
>>
>> With this move it's not necessary to have clamp_t calls anymore because
>> the verify callback is called when setting limits.
> 
> While testing this series, I observed that with amd_pstate=passive + schedutil governor,
> the scaling_max_freq limits were not being honored and I bisected the issue down to this
> patch.
> 
> I went through the code and noticed that in amd_pstate_adjust_perf(), we set the min_perf
> field in MSR_AMD_CPPC_REQ to "cap_perf" which is equal to cpudata->highest_perf (which is
> equal to 255 for non-preferred cores systems). This didnt seem logical to me and I changed
> cap_perf to cpudata->max_limit_perf which gives us the value updated in scaling_max_freq.
> 
> I think as we removed the redundant clamping code, this pre-existing issue got exposed.
> The below diff fixes the issue for me.
> 
> Please let me know your thoughts on this.
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index d7b1de97727a..1ac34e3f1fc5 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -699,7 +699,7 @@ static void amd_pstate_adjust_perf(unsigned int cpu,
>          if (min_perf < lowest_nonlinear_perf)
>                  min_perf = lowest_nonlinear_perf;
> 
> -       max_perf = cap_perf;
> +       max_perf = cpudata->max_limit_perf;
>          if (max_perf < min_perf)
>                  max_perf = min_perf;

With this change I think you can also drop the comparison afterwards, as 
an optimization right?

As this is already in superm1.git/linux-next after testing can you 
please send a patch relative to superm1.git/linux-next branch?

Thanks!

> 
> Thanks,
> Dhananjay
> 
>>
>> Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
>> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
>> ---
>> v2:
>>   * Drop lowest_perf variable
>> ---
>>   drivers/cpufreq/amd-pstate.c | 28 +++++-----------------------
>>   1 file changed, 5 insertions(+), 23 deletions(-)
>>
>> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
>> index 3a3df67c096d5..dc3c45b6f5103 100644
>> --- a/drivers/cpufreq/amd-pstate.c
>> +++ b/drivers/cpufreq/amd-pstate.c
>> @@ -537,10 +537,6 @@ static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf,
>>   	u32 nominal_perf = READ_ONCE(cpudata->nominal_perf);
>>   	u64 value = prev;
>>   
>> -	min_perf = clamp_t(unsigned long, min_perf, cpudata->min_limit_perf,
>> -			cpudata->max_limit_perf);
>> -	max_perf = clamp_t(unsigned long, max_perf, cpudata->min_limit_perf,
>> -			cpudata->max_limit_perf);
>>   	des_perf = clamp_t(unsigned long, des_perf, min_perf, max_perf);
>>   
>>   	max_freq = READ_ONCE(cpudata->max_limit_freq);
>> @@ -607,7 +603,7 @@ static int amd_pstate_verify(struct cpufreq_policy_data *policy_data)
>>   
>>   static int amd_pstate_update_min_max_limit(struct cpufreq_policy *policy)
>>   {
>> -	u32 max_limit_perf, min_limit_perf, lowest_perf, max_perf, max_freq;
>> +	u32 max_limit_perf, min_limit_perf, max_perf, max_freq;
>>   	struct amd_cpudata *cpudata = policy->driver_data;
>>   
>>   	max_perf = READ_ONCE(cpudata->highest_perf);
>> @@ -615,12 +611,8 @@ static int amd_pstate_update_min_max_limit(struct cpufreq_policy *policy)
>>   	max_limit_perf = div_u64(policy->max * max_perf, max_freq);
>>   	min_limit_perf = div_u64(policy->min * max_perf, max_freq);
>>   
>> -	lowest_perf = READ_ONCE(cpudata->lowest_perf);
>> -	if (min_limit_perf < lowest_perf)
>> -		min_limit_perf = lowest_perf;
>> -
>> -	if (max_limit_perf < min_limit_perf)
>> -		max_limit_perf = min_limit_perf;
>> +	if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE)
>> +		min_limit_perf = min(cpudata->nominal_perf, max_limit_perf);
>>   
>>   	WRITE_ONCE(cpudata->max_limit_perf, max_limit_perf);
>>   	WRITE_ONCE(cpudata->min_limit_perf, min_limit_perf);
>> @@ -1562,28 +1554,18 @@ static void amd_pstate_epp_cpu_exit(struct cpufreq_policy *policy)
>>   static int amd_pstate_epp_update_limit(struct cpufreq_policy *policy)
>>   {
>>   	struct amd_cpudata *cpudata = policy->driver_data;
>> -	u32 max_perf, min_perf;
>>   	u64 value;
>>   	s16 epp;
>>   
>> -	max_perf = READ_ONCE(cpudata->highest_perf);
>> -	min_perf = READ_ONCE(cpudata->lowest_perf);
>>   	amd_pstate_update_min_max_limit(policy);
>>   
>> -	max_perf = clamp_t(unsigned long, max_perf, cpudata->min_limit_perf,
>> -			cpudata->max_limit_perf);
>> -	min_perf = clamp_t(unsigned long, min_perf, cpudata->min_limit_perf,
>> -			cpudata->max_limit_perf);
>>   	value = READ_ONCE(cpudata->cppc_req_cached);
>>   
>> -	if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE)
>> -		min_perf = min(cpudata->nominal_perf, max_perf);
>> -
>>   	value &= ~(AMD_CPPC_MAX_PERF_MASK | AMD_CPPC_MIN_PERF_MASK |
>>   		   AMD_CPPC_DES_PERF_MASK);
>> -	value |= FIELD_PREP(AMD_CPPC_MAX_PERF_MASK, max_perf);
>> +	value |= FIELD_PREP(AMD_CPPC_MAX_PERF_MASK, cpudata->max_limit_perf);
>>   	value |= FIELD_PREP(AMD_CPPC_DES_PERF_MASK, 0);
>> -	value |= FIELD_PREP(AMD_CPPC_MIN_PERF_MASK, min_perf);
>> +	value |= FIELD_PREP(AMD_CPPC_MIN_PERF_MASK, cpudata->min_limit_perf);
>>   
>>   	/* Get BIOS pre-defined epp value */
>>   	epp = amd_pstate_get_epp(cpudata, value);
>