Re: [PATCH 1/4] cpufreq: amd_pstate: Add guided autonomous mode

Wyes Karny
2022-12-09T10:05:03Z

Hi Ray,

On 12/9/2022 1:13 PM, Huang Rui wrote:
> On Wed, Dec 07, 2022 at 11:46:45PM +0800, Karny, Wyes wrote:
>> From ACPI spec below 3 modes for CPPC can be defined:
>> 1. Non autonomous: OS scaling governor specifies operating frequency/
>> performance level through `Desired Performance` register and PMFW
>> follows that.
>> 2. Guided autonomous: OS scaling governor specifies min and max
>> frequencies/ performance levels through `Minimum Performance` and
>> `Maximum Performance` register, and PMFW can autonomously select an
>> operating frequency in this range.
>> 3. Fully autonomous: OS only hints (via EPP) to PMFW for the required
>> energy performance preference for the workload and PMFW autonomously
>> scales the frequency.
>>
>> Currently (1) is supported by amd_pstate as passive mode, and (3) is
>> implemented by EPP support. This change is to support (2).
>>
>> In guided autonomous mode the min_perf is based on the input from the
>> scaling governor. For example, in case of schedutil this value depends
>> on the current utilization. And max_perf is set to max capacity.
>>
>> To activate guided auto mode ``amd_pstate=guided`` command line
>> parameter has to be passed in the kernel.
>>
>> Signed-off-by: Wyes Karny <wyes.karny@amd.com>
>> ---
>> .../admin-guide/kernel-parameters.txt | 4 ++
>> drivers/cpufreq/amd-pstate.c | 60 +++++++++++++++----
>> 2 files changed, 53 insertions(+), 11 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index 42af9ca0127e..75e57afba77e 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -6970,3 +6970,7 @@
>> management firmware translates the requests into actual
>> hardware states (core frequency, data fabric and memory
>> clocks etc.)
>> + guided
>> + Activate guided autonomous mode. Driver requests minimum
>> + performance and maximum performance and the PMFW autonomously
>> + selects frequencies in this range.
>> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
>> index 204e39006dda..05e4003a77ee 100644
>> --- a/drivers/cpufreq/amd-pstate.c
>> +++ b/drivers/cpufreq/amd-pstate.c
>> @@ -50,6 +50,20 @@
>> #define AMD_PSTATE_TRANSITION_LATENCY 20000
>> #define AMD_PSTATE_TRANSITION_DELAY 1000
>>
>> +enum amd_pstate_mode {
>> + CPPC_DISABLE = 0,
>> + CPPC_PASSIVE,
>> + CPPC_GUIDED,
>> + CPPC_MODE_MAX,
>> +};
>> +
>> +static const char * const amd_pstate_mode_string[] = {
>> + [CPPC_DISABLE] = "disable",
>> + [CPPC_PASSIVE] = "passive",
>> + [CPPC_GUIDED] = "guided",
>> + NULL,
>> +};
>> +
>> /*
>> * TODO: We need more time to fine tune processors with shared memory solution
>> * with community together.
>> @@ -60,7 +74,18 @@
>> * module parameter to be able to enable it manually for debugging.
>> */
>> static struct cpufreq_driver amd_pstate_driver;
>> -static int cppc_load __initdata;
>> +static int cppc_state = CPPC_DISABLE;
>> +
>> +static inline int get_mode_idx_from_str(const char *str, size_t size)
>> +{
>> + int i = 0;
>> +
>> + for (; i < CPPC_MODE_MAX; ++i) {
>> + if (!strncmp(str, amd_pstate_mode_string[i], size))
>> + return i;
>> + }
>> + return -EINVAL;
>> +}
>>
>> static inline int pstate_enable(bool enable)
>> {
>> @@ -212,12 +237,18 @@ static inline bool amd_pstate_sample(struct amd_cpudata *cpudata)
>> }
>>
>> static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf,
>> - u32 des_perf, u32 max_perf, bool fast_switch)
>> + u32 des_perf, u32 max_perf, bool fast_switch, int flags)
>> {
>> u64 prev = READ_ONCE(cpudata->cppc_req_cached);
>> u64 value = prev;
>>
>> des_perf = clamp_t(unsigned long, des_perf, min_perf, max_perf);
>> +
>> + if (cppc_state == CPPC_GUIDED && flags & CPUFREQ_GOV_DYNAMIC_SWITCHING) {
>> + min_perf = des_perf;
>> + des_perf = 0;
>> + }
>
> Since we would like to modify the min_perf on share memory processors as
> well. The current cppc_set_perf() in cppc_acpi doesn't provide the MIN/MAX
> values. Could you please add the max_perf/min_perf in cppc_acpi.c as well?
> Then the APIs will be available on the share memory processors like Rome.

Sure. Thanks for pointing this out.

>
> Thanks,
> Ray
>
>> +
>> value &= ~AMD_CPPC_MIN_PERF(~0L);
>> value |= AMD_CPPC_MIN_PERF(min_perf);
>>
>> @@ -272,7 +303,7 @@ static int amd_pstate_target(struct cpufreq_policy *policy,
>>
>> cpufreq_freq_transition_begin(policy, &freqs);
>> amd_pstate_update(cpudata, min_perf, des_perf,
>> - max_perf, false);
>> + max_perf, false, policy->governor->flags);
>> cpufreq_freq_transition_end(policy, &freqs, false);
>>
>> return 0;
>> @@ -306,7 +337,8 @@ static void amd_pstate_adjust_perf(unsigned int cpu,
>> if (max_perf < min_perf)
>> max_perf = min_perf;
>>
>> - amd_pstate_update(cpudata, min_perf, des_perf, max_perf, true);
>> + amd_pstate_update(cpudata, min_perf, des_perf, max_perf, true,
>> + policy->governor->flags);
>> }
>>
>> static int amd_get_min_freq(struct amd_cpudata *cpudata)
>> @@ -627,7 +659,7 @@ static int __init amd_pstate_init(void)
>> * enable the amd_pstate passive mode driver explicitly
>> * with amd_pstate=passive in kernel command line
>> */
>> - if (!cppc_load) {
>> + if (cppc_state == CPPC_DISABLE) {
>> pr_debug("driver load is disabled, boot with amd_pstate=passive to enable this\n");
>> return -ENODEV;
>> }
>> @@ -670,16 +702,22 @@ device_initcall(amd_pstate_init);
>>
>> static int __init amd_pstate_param(char *str)
>> {
>> + int size, mode_idx;
>> +
>> if (!str)
>> return -EINVAL;
>>
>> - if (!strcmp(str, "disable")) {
>> - cppc_load = 0;
>> - pr_info("driver is explicitly disabled\n");
>> - } else if (!strcmp(str, "passive"))
>> - cppc_load = 1;
>> + size = strlen(str);
>> + mode_idx = get_mode_idx_from_str(str, size);
>>
>> - return 0;
>> + if (mode_idx >= CPPC_DISABLE && mode_idx < CPPC_MODE_MAX) {
>> + cppc_state = mode_idx;
>> + if (cppc_state == CPPC_DISABLE)
>> + pr_info("driver is explicitly disabled\n");
>> + return 0;
>> + }
>> +
>> + return -EINVAL;
>> }
>> early_param("amd_pstate", amd_pstate_param);
>>
>> --
>> 2.34.1
>>

--
Thanks & Regards,
Wyes