Re: [PATCH 5/8] x86/amd: Detect preferred cores in amd_get_boost_ratio_numerator()

Mario Limonciello
2024-08-27T19:00:52Z

On 8/27/2024 10:43, Gautham R. Shenoy wrote:
>
> On Mon, Aug 26, 2024 at 04:13:55PM -0500, Mario Limonciello wrote:
>> From: Mario Limonciello <mario.limonciello@amd.com>
>>
>> AMD systems that support preferred cores will use "166" as their
>> numerator for max frequency calculations instead of "255".
>>
>> Add a function for detecting preferred cores by looking at the
>> highest perf value on all cores.
>>
>> If preferred cores are enabled return 166 and if disabled the
>> value in the highest perf register. As the function will be called
>> multiple times, cache the values for the boost numerator and if
>> preferred cores will be enabled in global variables.
>>
>> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
>> ---
>
> [..snip..]
>
>> /**
>> * amd_get_boost_ratio_numerator: Get the numerator to use for boost ratio calculation
>> * @cpu: CPU to get numerator for.
>> @@ -162,20 +232,19 @@ EXPORT_SYMBOL_GPL(amd_get_highest_perf);
>> */
>> int amd_get_boost_ratio_numerator(unsigned int cpu, u64 *numerator)
>> {
>> - struct cpuinfo_x86 *c = &boot_cpu_data;
>> + bool prefcore;
>> + int ret;
>>
>> - if (c->x86 == 0x17 && ((c->x86_model >= 0x30 && c->x86_model < 0x40) ||
>> - (c->x86_model >= 0x70 && c->x86_model < 0x80))) {
>> - *numerator = 166;
>> - return 0;
>> - }
>> + ret = amd_detect_prefcore(&prefcore);
>> + if (ret)
>> + return ret;
>>
>> - if (c->x86 == 0x19 && ((c->x86_model >= 0x20 && c->x86_model < 0x30) ||
>> - (c->x86_model >= 0x40 && c->x86_model < 0x70))) {
>> - *numerator = 166;
>> + /* without preferred cores, return the highest perf register value */
>> + if (!prefcore) {
>> + *numerator = boost_numerator;
>> return 0;
>> }
>> - *numerator = 255;
>> + *numerator = CPPC_HIGHEST_PERF_PREFCORE;
>
>
> Interesting. So even when the user boots a system that supports
> preferred-cores with "amd_preferred=disable",
> amd_get_boost_ratio_numerator() will return CPPC_HIGHEST_PERF_PREFCORE
> as the call prefcore == true here.
>
> I suppose that is as intended, since even though the user may not want
> to use the preferred core logic for task-scheduling/load-balancing,
> the numerator for the boost-ratio is purely dependent on the h/w
> capability.
>
> Is this understanding correct? If so, can this be included as a
> comment in the code ?
>

Yup, you got it all right. I'll fold some of this into the function
comment for v2.

> The rest of the patch looks good to me.
>
> Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
>
> --
> Thanks and Regards
> gautham.
>
>
>
>>
>> return 0;
>> }
>> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
>> index f470b5700db58..ec32c830abc1d 100644
>> --- a/drivers/cpufreq/amd-pstate.c
>> +++ b/drivers/cpufreq/amd-pstate.c
>> @@ -807,32 +807,18 @@ static DECLARE_WORK(sched_prefcore_work, amd_pstste_sched_prefcore_workfn);
>>
>> static void amd_pstate_init_prefcore(struct amd_cpudata *cpudata)
>> {
>> - int ret, prio;
>> - u32 highest_perf;
>> -
>> - ret = amd_get_highest_perf(cpudata->cpu, &highest_perf);
>> - if (ret)
>> + /* user disabled or not detected */
>> + if (!amd_pstate_prefcore)
>> return;
>>
>> cpudata->hw_prefcore = true;
>> - /* check if CPPC preferred core feature is enabled*/
>> - if (highest_perf < CPPC_MAX_PERF)
>> - prio = (int)highest_perf;
>> - else {
>> - pr_debug("AMD CPPC preferred core is unsupported!\n");
>> - cpudata->hw_prefcore = false;
>> - return;
>> - }
>> -
>> - if (!amd_pstate_prefcore)
>> - return;
>>
>> /*
>> * The priorities can be set regardless of whether or not
>> * sched_set_itmt_support(true) has been called and it is valid to
>> * update them at any time after it has been called.
>> */
>> - sched_set_itmt_core_prio(prio, cpudata->cpu);
>> + sched_set_itmt_core_prio((int)READ_ONCE(cpudata->highest_perf), cpudata->cpu);
>>
>> schedule_work(&sched_prefcore_work);
>> }
>> @@ -998,12 +984,12 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
>>
>> cpudata->cpu = policy->cpu;
>>
>> - amd_pstate_init_prefcore(cpudata);
>> -
>> ret = amd_pstate_init_perf(cpudata);
>> if (ret)
>> goto free_cpudata1;
>>
>> + amd_pstate_init_prefcore(cpudata);
>> +
>> ret = amd_pstate_init_freq(cpudata);
>> if (ret)
>> goto free_cpudata1;
>> @@ -1453,12 +1439,12 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
>> cpudata->cpu = policy->cpu;
>> cpudata->epp_policy = 0;
>>
>> - amd_pstate_init_prefcore(cpudata);
>> -
>> ret = amd_pstate_init_perf(cpudata);
>> if (ret)
>> goto free_cpudata1;
>>
>> + amd_pstate_init_prefcore(cpudata);
>> +
>> ret = amd_pstate_init_freq(cpudata);
>> if (ret)
>> goto free_cpudata1;
>> @@ -1903,6 +1889,12 @@ static int __init amd_pstate_init(void)
>> static_call_update(amd_pstate_update_perf, cppc_update_perf);
>> }
>>
>> + if (amd_pstate_prefcore) {
>> + ret = amd_detect_prefcore(&amd_pstate_prefcore);
>> + if (ret)
>> + return ret;
>> + }
>> +
>> /* enable amd pstate feature */
>> ret = amd_pstate_enable(true);
>> if (ret) {
>> diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h
>> index 2246ce0630362..1d79320a23490 100644
>> --- a/include/acpi/cppc_acpi.h
>> +++ b/include/acpi/cppc_acpi.h
>> @@ -137,10 +137,12 @@ struct cppc_cpudata {
>> };
>>
>> #ifdef CONFIG_CPU_SUP_AMD
>> +extern int amd_detect_prefcore(bool *detected);
>> extern int amd_get_highest_perf(unsigned int cpu, u32 *highest_perf);
>> extern int amd_get_boost_ratio_numerator(unsigned int cpu, u64 *numerator);
>> #else /* !CONFIG_CPU_SUP_AMD */
>> static inline int amd_get_highest_perf(unsigned int cpu, u32 *highest_perf) { return -ENODEV; }
>> +static inline int amd_detect_prefcore(bool *detected) { return -ENODEV; }
>> static inline int amd_get_boost_ratio_numerator(unsigned int cpu, u64 *numerator) { return -ENODEV; }
>> #endif /* !CONFIG_CPU_SUP_AMD */
>>
>> --
>> 2.43.0
>>