[PATCH] cpufreq: intel_pstate: allow trace in passive mode

[Doug Smythies]

Allow use of the trace_pstate_sample trace function
when the intel_pstate driver is in passive mode.
Since the core_busy and scaled_busy fields are not
used, and it might be desirable to know which path
through the driver was used, either intel_cpufreq_target
or intel_cpufreq_fast_switch, re-task the core_busy
field as a flag indicator.

The user can then use the intel_pstate_tracer.py utility
to summarize and plot the trace.

In Passive mode the driver is only called if there is
a need to change the target frequency, so durations
(time gaps between calls) can be very very long. The user
needs to understand, and not be confused by, this limitation.

Signed-off-by: Doug Smythies <dsmyth...@telus.net>
---
 drivers/cpufreq/intel_pstate.c | 50 ++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 48 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 283491f..04e91ed 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -2271,7 +2271,10 @@ static int intel_cpufreq_target(struct cpufreq_policy 
*policy,
 {
        struct cpudata *cpu = all_cpu_data[policy->cpu];
        struct cpufreq_freqs freqs;
-       int target_pstate;
+       struct sample *sample;
+       int target_pstate, from;
+       u64 time;
+       bool sample_taken;
 
        update_turbo_state();
 
@@ -2291,12 +2294,32 @@ static int intel_cpufreq_target(struct cpufreq_policy 
*policy,
                break;
        }
        target_pstate = intel_pstate_prepare_request(cpu, target_pstate);
+
+       from = cpu->pstate.current_pstate;
+       time = ktime_get();
+       sample_taken = intel_pstate_sample(cpu, time);
+
        if (target_pstate != cpu->pstate.current_pstate) {
                cpu->pstate.current_pstate = target_pstate;
                wrmsrl_on_cpu(policy->cpu, MSR_IA32_PERF_CTL,
                              pstate_funcs.get_val(cpu, target_pstate));
        }
        freqs.new = target_pstate * cpu->pstate.scaling;
+
+       if (sample_taken) {
+               intel_pstate_calc_avg_perf(cpu);
+               sample = &cpu->sample;
+               trace_pstate_sample(0,
+               0,
+               from,
+               cpu->pstate.current_pstate,
+               sample->mperf,
+               sample->aperf,
+               sample->tsc,
+               get_avg_frequency(cpu),
+               fp_toint(cpu->iowait_boost * 100));
+       }
+
        cpufreq_freq_transition_end(policy, &freqs, false);
 
        return 0;
@@ -2306,13 +2329,36 @@ static unsigned int intel_cpufreq_fast_switch(struct 
cpufreq_policy *policy,
                                              unsigned int target_freq)
 {
        struct cpudata *cpu = all_cpu_data[policy->cpu];
-       int target_pstate;
+       struct sample *sample;
+       int target_pstate, from;
+       u64 time;
+       bool sample_taken;
 
        update_turbo_state();
 
        target_pstate = DIV_ROUND_UP(target_freq, cpu->pstate.scaling);
        target_pstate = intel_pstate_prepare_request(cpu, target_pstate);
+
+       from = cpu->pstate.current_pstate;
+       time = ktime_get();
+       sample_taken = intel_pstate_sample(cpu, time);
+
        intel_pstate_update_pstate(cpu, target_pstate);
+
+       if (sample_taken) {
+               intel_pstate_calc_avg_perf(cpu);
+               sample = &cpu->sample;
+               trace_pstate_sample(100,
+               0,
+               from,
+               cpu->pstate.current_pstate,
+               sample->mperf,
+               sample->aperf,
+               sample->tsc,
+               get_avg_frequency(cpu),
+               fp_toint(cpu->iowait_boost * 100));
+       }
+
        return target_pstate * cpu->pstate.scaling;
 }
 
-- 
2.7.4