`Hi Vincent,On 21/11/17 17:08, Vincent Guittot wrote:> Hi Lukasz>> On 21 November 2017 at 16:56, Lukasz Luba <llu.ker.dev@gmail.com> wrote:>> On 21/11/17 14:06, Daniel Lezcano wrote:>>>>>> On 21/11/2017 12:30, Ionela Voinescu wrote:>>>>>> [ ... ]>>>>>>> A DT model would be easy to support with the current code but it would>>>> be very inaccurate.>>>>>>>>> Why ?>>>>>> [ ... ]>>>>> Hi all,>>>> The DT solution won't fly, the reason can be found below.>>>> I agree with Ionela and Punit that the Juno board is not>> the best platform to test the static power impact on IPA.>> In some other platforms the static power can be 50% or more>> of the total power, so it cannot be neglected.>>>> These are the issues.>> The static power equation is complicated, here is one known to me.>> The leakage function is exponentially influenced by current circuit>> supply voltage, body-bias and some constants K_{4,5}.>>>> P_{leak} = L_{g}*V_{dd}*K_{3}*e^{K_{4}*V_{dd}}*e^{K_{5}*V_{bs}}+|>> V_{bs}|*I_{Ju}>> You forgot one main contributor of static leakage: the temperatureYes, so basically, the relation between temperature and the poweris exponential. The power doubles every 20deg.You can find this model for static power for Mali GPU:https://chromium.googlesource.com/chromiumos/third_party/kernel/+/stabilize-8743.60.B-chromeos-4.4/drivers/gpu/arm/midgard/backend/gpu/mali_kbase_power_model_simple.c#37There is a polynomial which approximates it for gpu (starting fromline 56).>>>>> It can also vary depending on technology (CMOS, FinFET, etc).>>>> It would be really hard to approximate by i.e. a polynomial>> function with inputs from DT. One size does not fit all.>> But can't we linearized around the target temp ? that were we want to> be accurateI would also add: 'around the target temp' and starting at least fromIPA enable trip point (so i.e. from 55degC to 75degC + margin)I would have to simulate it and see some results to see error values.Of course it would be better that having no static power at all,but the vendors would have create a tool which calculates the factorsand put them to DT.Regards,Lukasz`