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Above this threshold, lower performance levels > generally result in increased energy efficiency. Reducing performance > below this threshold does not result in total energy savings for a given > computation, although it reduces instantaneous power consumption". So > lowest_nonlinear_perf is the most power efficient performance level, and > going below that would lead to a worse performance/watt. > > Also, setting the minimum frequency to lowest_nonlinear_freq (instead of > lowest_freq) allows the CPU to idle at a higher frequency which leads > to more time being spent in a deeper idle state (as trivial idle tasks > are completed sooner). This has shown a power benefit in some systems, > in other systems, power consumption has increased but so has the > throughput/watt. > > Modify the initial policy_data->min set by cpufreq-core to > lowest_nonlinear_freq, in the ->verify() callback. Also set the > cpudata->req[0] to FREQ_QOS_MIN_DEFAULT_VALUE (i.e. 0), so that it also > gets overriden by the check in verify function. > > Link: https://www.amd.com/content/dam/amd/en/documents/processor-tech-docs/programmer-references/24593.pdf [1] > > Signed-off-by: Dhananjay Ugwekar Thanks for the fixes, I'll queue this series up. Reviewed-by: Mario Limonciello > --- > drivers/cpufreq/amd-pstate.c | 21 ++++++++++++++++++++- > 1 file changed, 20 insertions(+), 1 deletion(-) > > diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c > index fa16d72d6058..833fc17a39f2 100644 > --- a/drivers/cpufreq/amd-pstate.c > +++ b/drivers/cpufreq/amd-pstate.c > @@ -529,8 +529,27 @@ static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf, > > static int amd_pstate_verify(struct cpufreq_policy_data *policy_data) > { > + /* > + * Initialize lower frequency limit (i.e.policy->min) with > + * lowest_nonlinear_frequency which is the most energy efficient > + * frequency. Override the initial value set by cpufreq core and > + * amd-pstate qos_requests. > + */ > + if (policy_data->min == FREQ_QOS_MIN_DEFAULT_VALUE) { > + struct cpufreq_policy *policy = cpufreq_cpu_get(policy_data->cpu); > + struct amd_cpudata *cpudata; > + > + if (!policy) > + return -EINVAL; > + > + cpudata = policy->driver_data; > + policy_data->min = cpudata->lowest_nonlinear_freq; > + cpufreq_cpu_put(policy); > + } > + > cpufreq_verify_within_cpu_limits(policy_data); > pr_debug("policy_max =%d, policy_min=%d\n", policy_data->max, policy_data->min); > + > return 0; > } > > @@ -996,7 +1015,7 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy) > policy->fast_switch_possible = true; > > ret = freq_qos_add_request(&policy->constraints, &cpudata->req[0], > - FREQ_QOS_MIN, policy->cpuinfo.min_freq); > + FREQ_QOS_MIN, FREQ_QOS_MIN_DEFAULT_VALUE); > if (ret < 0) { > dev_err(dev, "Failed to add min-freq constraint (%d)\n", ret); > goto free_cpudata1;