Re: [PATCH v3 18/18] cpufreq/amd-pstate: Stop caching EPP

From: Gautham R. Shenoy
Date: Wed Feb 19 2025 - 10:45:47 EST


On Mon, Feb 17, 2025 at 04:07:07PM -0600, Mario Limonciello wrote:
> From: Mario Limonciello <mario.limonciello@xxxxxxx>
>
> EPP values are cached in the cpudata structure per CPU. This is needless
> though because they are also cached in the CPPC request variable.
>
> Drop the separate cache for EPP values and always reference the CPPC
> request variable when needed.
>
> Reviewed-by: Dhananjay Ugwekar <dhananjay.ugwekar@xxxxxxx>
> Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>

LGTM

Reviewed-by: Gautham R. Shenoy <gautham.shenoy@xxxxxxx>


--
Thanks and Regards
gautham.

> ---
> drivers/cpufreq/amd-pstate.c | 27 ++++++++++++++-------------
> drivers/cpufreq/amd-pstate.h | 1 -
> 2 files changed, 14 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 4660dd3f04796..48ec5e6527c68 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -268,8 +268,6 @@ static int msr_update_perf(struct cpufreq_policy *policy, u8 min_perf,
> }
>
> WRITE_ONCE(cpudata->cppc_req_cached, value);
> - if (epp != cpudata->epp_cached)
> - WRITE_ONCE(cpudata->epp_cached, epp);
>
> return 0;
> }
> @@ -318,7 +316,6 @@ static int msr_set_epp(struct cpufreq_policy *policy, u8 epp)
> }
>
> /* update both so that msr_update_perf() can effectively check */
> - WRITE_ONCE(cpudata->epp_cached, epp);
> WRITE_ONCE(cpudata->cppc_req_cached, value);
>
> return ret;
> @@ -335,9 +332,12 @@ static int shmem_set_epp(struct cpufreq_policy *policy, u8 epp)
> {
> struct amd_cpudata *cpudata = policy->driver_data;
> struct cppc_perf_ctrls perf_ctrls;
> + u8 epp_cached;
> u64 value;
> int ret;
>
> +
> + epp_cached = FIELD_GET(AMD_CPPC_EPP_PERF_MASK, cpudata->cppc_req_cached);
> if (trace_amd_pstate_epp_perf_enabled()) {
> union perf_cached perf = cpudata->perf;
>
> @@ -348,10 +348,10 @@ static int shmem_set_epp(struct cpufreq_policy *policy, u8 epp)
> FIELD_GET(AMD_CPPC_MAX_PERF_MASK,
> cpudata->cppc_req_cached),
> policy->boost_enabled,
> - epp != cpudata->epp_cached);
> + epp != epp_cached);
> }
>
> - if (epp == cpudata->epp_cached)
> + if (epp == epp_cached)
> return 0;
>
> perf_ctrls.energy_perf = epp;
> @@ -360,7 +360,6 @@ static int shmem_set_epp(struct cpufreq_policy *policy, u8 epp)
> pr_debug("failed to set energy perf value (%d)\n", ret);
> return ret;
> }
> - WRITE_ONCE(cpudata->epp_cached, epp);
>
> value = READ_ONCE(cpudata->cppc_req_cached);
> value &= ~AMD_CPPC_EPP_PERF_MASK;
> @@ -1203,9 +1202,11 @@ static ssize_t show_energy_performance_preference(
> struct cpufreq_policy *policy, char *buf)
> {
> struct amd_cpudata *cpudata = policy->driver_data;
> - u8 preference;
> + u8 preference, epp;
> +
> + epp = FIELD_GET(AMD_CPPC_EPP_PERF_MASK, cpudata->cppc_req_cached);
>
> - switch (cpudata->epp_cached) {
> + switch (epp) {
> case AMD_CPPC_EPP_PERFORMANCE:
> preference = EPP_INDEX_PERFORMANCE;
> break;
> @@ -1568,7 +1569,7 @@ static int amd_pstate_epp_update_limit(struct cpufreq_policy *policy)
> if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE)
> epp = 0;
> else
> - epp = READ_ONCE(cpudata->epp_cached);
> + epp = FIELD_GET(AMD_CPPC_EPP_PERF_MASK, cpudata->cppc_req_cached);
>
> perf = READ_ONCE(cpudata->perf);
>
> @@ -1604,22 +1605,22 @@ static int amd_pstate_epp_cpu_online(struct cpufreq_policy *policy)
> struct amd_cpudata *cpudata = policy->driver_data;
> union perf_cached perf = READ_ONCE(cpudata->perf);
> int ret;
> + u8 epp;
> +
> + epp = FIELD_GET(AMD_CPPC_EPP_PERF_MASK, cpudata->cppc_req_cached);
>
> pr_debug("AMD CPU Core %d going online\n", cpudata->cpu);
>
> ret = amd_pstate_cppc_enable(policy);
> if (ret)
> return ret;
> -
> -
> - ret = amd_pstate_update_perf(policy, 0, 0, perf.highest_perf, cpudata->epp_cached, false);
> + ret = amd_pstate_update_perf(policy, 0, 0, perf.highest_perf, epp, false);
> if (ret)
> return ret;
>
> cpudata->suspended = false;
>
> return 0;
> -
> }
>
> static int amd_pstate_epp_cpu_offline(struct cpufreq_policy *policy)
> diff --git a/drivers/cpufreq/amd-pstate.h b/drivers/cpufreq/amd-pstate.h
> index 1a52582dbac9d..13918853f0a82 100644
> --- a/drivers/cpufreq/amd-pstate.h
> +++ b/drivers/cpufreq/amd-pstate.h
> @@ -100,7 +100,6 @@ struct amd_cpudata {
> bool hw_prefcore;
>
> /* EPP feature related attributes*/
> - u8 epp_cached;
> u32 policy;
> bool suspended;
> u8 epp_default;
> --
> 2.43.0
>