Hi George, On 6/15/2018 4:03 AM, George Cherian wrote: > Per Section 8.4.7.1.3 of ACPI 6.2, The platform provides performance > feedback via set of performance counters. To determine the actual > performance level delivered over time, OSPM may read a set of > performance counters from the Reference Performance Counter Register > and the Delivered Performance Counter Register. > > OSPM calculates the delivered performance over a given time period by > taking a beginning and ending snapshot of both the reference and > delivered performance counters, and calculating: > > delivered_perf = reference_perf X (delta of delivered_perf counter / delta of > reference_perf counter). > > Implement the above and hook this to the cpufreq->get method. > > Signed-off-by: George Cherian <george.cher...@cavium.com> > Acked-by: Viresh Kumar <viresh.ku...@linaro.org> > --- > drivers/cpufreq/cppc_cpufreq.c | 71 > ++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 71 insertions(+) > > diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c > index 3464580..3fe7625 100644 > --- a/drivers/cpufreq/cppc_cpufreq.c > +++ b/drivers/cpufreq/cppc_cpufreq.c > @@ -296,10 +296,81 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy > *policy) > return ret; > } > > +static int cppc_get_rate_from_fbctrs(struct cppc_cpudata *cpu, > + struct cppc_perf_fb_ctrs fb_ctrs_t0, > + struct cppc_perf_fb_ctrs fb_ctrs_t1) > +{ > + u64 delta_reference, delta_delivered; > + u64 reference_perf, delivered_perf; > + > + reference_perf = fb_ctrs_t0.reference_perf; > + if (fb_ctrs_t1.reference > fb_ctrs_t0.reference) { > + delta_reference = fb_ctrs_t1.reference - fb_ctrs_t0.reference; > + } else { There should be another if () here to check if the reference counters are equal. We cannot assume, there was a overflow when the counters are equal. As I mentioned on last patch, the counters *may* pause in idle states. > + /* > + * Counters would have wrapped-around > + * We also need to find whether the low level fw > + * maintains 32 bit or 64 bit counters, to calculate > + * the correct delta. > + */ > + if (fb_ctrs_t0.reference > (~(u32)0)) > + delta_reference = (~((u64)0) - fb_ctrs_t0.reference) + > + fb_ctrs_t1.reference; > + else > + delta_reference = (~((u32)0) - fb_ctrs_t0.reference) + > + fb_ctrs_t1.reference; > + } > + > + if (fb_ctrs_t1.delivered > fb_ctrs_t0.delivered) { > + delta_delivered = fb_ctrs_t1.delivered - fb_ctrs_t0.delivered; > + } else { > + /* > + * Counters would have wrapped-around > + * We also need to find whether the low level fw > + * maintains 32 bit or 64 bit counters, to calculate > + * the correct delta. > + */ > + if (fb_ctrs_t0.delivered > (~(u32)0)) > + delta_delivered = (~((u64)0) - fb_ctrs_t0.delivered) + > + fb_ctrs_t1.delivered; > + else > + delta_delivered = (~((u32)0) - fb_ctrs_t0.delivered) + > + fb_ctrs_t1.delivered; > + } > + > + if (delta_reference) /* Check to avoid divide-by zero */ > + delivered_perf = (reference_perf * delta_delivered) / > + delta_reference; > + else > + delivered_perf = reference_perf;
If we cannot compute delivered performance then we should return desired/requested perf and not reference_perf. > + > + return cppc_cpufreq_perf_to_khz(cpu, delivered_perf); > +} > + > +static unsigned int cppc_cpufreq_get_rate(unsigned int cpunum) > +{ > + struct cppc_perf_fb_ctrs fb_ctrs_t0 = {0}, fb_ctrs_t1 = {0}; > + struct cppc_cpudata *cpu = all_cpu_data[cpunum]; > + int ret; > + > + ret = cppc_get_perf_ctrs(cpunum, &fb_ctrs_t0); > + if (ret) > + return ret; > + > + udelay(2); /* 2usec delay between sampling */ > + > + ret = cppc_get_perf_ctrs(cpunum, &fb_ctrs_t1); > + if (ret) > + return ret; > + > + return cppc_get_rate_from_fbctrs(cpu, fb_ctrs_t0, fb_ctrs_t1); > +} > + > static struct cpufreq_driver cppc_cpufreq_driver = { > .flags = CPUFREQ_CONST_LOOPS, > .verify = cppc_verify_policy, > .target = cppc_cpufreq_set_target, > + .get = cppc_cpufreq_get_rate, > .init = cppc_cpufreq_cpu_init, > .stop_cpu = cppc_cpufreq_stop_cpu, > .name = "cppc_cpufreq", Thanks, Prashanth