Messages in this thread | | | Date | Wed, 30 Jan 2019 10:23:13 +0000 | From | Quentin Perret <> | Subject | Re: [PATCH 6/7] arm64: dts: juno: Add cpu dynamic-power-coefficient information |
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On Tuesday 29 Jan 2019 at 15:27:35 (+0000), Sudeep Holla wrote: > On Mon, Jan 28, 2019 at 04:55:21PM +0000, Quentin Perret wrote: > > From: Dietmar Eggemann <dietmar.eggemann@arm.com> > > > > A CPUfreq driver, like the scpi driver used on Juno boards, which > > provide the Energy Model with power cost information via the PM_OPP > > of_dev_pm_opp_get_cpu_power() function, do need the > > dynamic-power-coefficient (C) in the device tree. > > > > Method used to obtain the C value: > > C is computed by measuring energy (E) consumption of a frequency domain > > (FD) over a 10s runtime (t) sysbench workload running at each Operating > > Performance Point (OPP) affine to 1 or 2 CPUs of that FD while the other > > CPUs of the system are hotplugged out. > > By definition all CPUs of a FD have the the same micro-architecture. An > > OPP is characterized by a certain frequency (f) and voltage (V) value. > > The corresponding power values (P) are calculated by dividing the delta > > of the E values between the runs with 2 and 1 CPUs by t. > > > > With n data tuples (P, f, V), n equal to number of OPPs for this > > frequency domain, we can solve C by: > > > > P = Pstat + Pdyn > > > > P = Pstat + CV²f > > > > Cx = (Px - P1)/(Vx²fx - V1²f1) with x = {2, ..., n} > > > > The C value is the arithmetic mean out of {C2, ..., Cn}. > > > > Since DVFS is broken on Juno r1, no dynamic-power-coefficient > > information has been added to its dts file. > > > > Since the binding for "dynamic-power-coefficient" property already exist, > and I don't see any dependency for this and the next patch(TC2) on this > series, I will apply them. Please shout if for any reason that's not true.
Thanks Sudeep ! Quentin
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