Quoting Andy Green (2013-08-05 01:32:41) > On 1 August 2013 14:26, Comaschi, F. <fcomaschi@xxxxxx> wrote: > > Somehow this just appeared today. > > > Dear Mike, > > > > yes I have seen Andy's presentation about using AEP, and I had the impression that some measurements would have been possible on my board. Could you tell me which is the exact reason why it is more advisable to use a NI DAQ rather than a AEP? I thought that an AEP would have integrated better with the ARM development chain of DS5. > > > > Also, could you please tell me what do you exactly mean by "Solder sense > > resistors across exposed capacitors"? > > I think Mike must have meant inductors; since the capacitors are > between the rail and 0V adding the shunts there will result in a > direct short across the rail hopefully triggering something's > overcurrent detection or if not "letting the smoke out" of your > low-value shunt resistor. > > (Also /Gross/Green/ ^^) Two embarrassing mistakes in one email. Yes I meant inductors and not caps. Please leave the caps alone. Thanks for the corrections Andy. Regards, Mike > > > Does it mean inserting a shunt resistors in series to an existing capacitor on the board? Would you or somebody else be able to suggest me any of such capacitors on the Arndale board? > > According to Andy' s presentation, I thought that the best way to do power measurement was rather looking for inductors on the input side of power regulators, and replace those ones with shunt resistors. > > That is correct. > > > Looking at the enclosed schematic, Andy told me that unfortunately it seems like the Arndale 5250 does not present any suitable spot where to perform accurate power measurements. > > I couldn't see anything useful to measure ARM Vcore, which is ironic > since there are so many other rails with shunt resistors already on > that board. > > -Andy > > > Could you please tell me more about this? > > > > Thanks again for all the provided information. > > > > Best regards, > > > > Francesco > > > > ________________________________________ > > From: Mike Turquette [mike.turquette@xxxxxxxxxx] > > Sent: Wednesday, July 31, 2013 5:58 AM > > To: Comaschi, F. > > Subject: Re: power measurement > > > > Quoting Comaschi, F. (2013-07-10 05:49:36) > >> Dear Mike, > >> > >> I am Francesco Comaschi, a researcher at Eindhoven University of Technology. I am sending you this email because my group is interested in purchasing an ARM-powered board where to measure power consumption with the highest accuracy possible. > >> Ideally, the board we are looking for has the following characteristics: > >> > >> -) options for power-saving strategies (DVFS and power gating); > >> -) options for measuring power consumption on the board (possibly via software, maybe using lm_sensors), or via hardware otherwise (maybe using ARM Energy Probe?); > >> -) support available: since I do not have much experience, i would rather choose an option where either some work has already been done in terms of power management/power measurements, or some sort of support would be guaranteed (for example, regarding the Arndale board I could not get to work the DVFS through Linaro, and so far I didn'get any answer/feed-back from In Signal). > >> > >> Also, if you have any documentation/tutorial/reference to suggest me in order to understand how to properly perform DVFS/power gating on one of the boards supported by Linaro, I would be really grateful. > >> I was considering, among the others, the Arndale dual-board (that we already have), the Origen quad-core board and the Panda board. Also the Versatile Express family from ARM is very attractive of course, but terribly expensive. > > > > Hi Francesco, > > > > Arndale and Panda are both good options which have some support upstream > > for DVFS and power gating. > > > >> I have read about the possibility of using the AEP to measure energy on device: > >> http://www.linaro.org/documents/download/3f44bb2b53ebd7ef498202d496c8cadd5093c0a862c4a > >> and I was wandering if anything similar has been already done on the Origen and the Arndale. > > > > AEP is very limiting. Did you see Andy Gross' presentation on using the > > AEP? It might be good for observing some DVFS transitions, but is > > essentially useless for high-accuracy low-power idle transitions. > > > > It is important to know that measuring high-performance workloads is not > > the same as measuing low power workloads. You might choose different > > resistor values depending on whether you are interested in measuring > > active frequency scaling versus idle power gating. > > > > There is still no easy way to do this. I suggest purchasing a National > > Instruments DAQ, one of the USB 6000 series should be good. Solder sense > > resistors across exposed capacitors on the boards and measure that way. > > It is how most of us do it when we want to get serious about measuring > > power. > > > > If you have further questions please Cc the Linux ARM kernel mailing > > list. It means more people can answer your questions and future > > researchers can benefit from your correspondence. > > > > Regards, > > Mike > > > >> > >> Also, from this page: > >> https://wiki.linaro.org/WorkingGroups/PowerManagement/Matrix1105 > >> is is not clear to me if the cpu_idle and cpu_freq frameworks (which I think are used for power gating and DVFS respectively) are up and running on the mentioned boards, and if it would be possible to manage DVFS and power-gating directly from inside my application. > >> > >> Sorry for all the questions, but any help would be very much appreciated. > >> > >> Thanks in advance for your kind attention, > >> > >> Best regards, > >> > >> Francesco Comaschi > > _______________________________________________ > > linaro-kernel mailing list > > linaro-kernel@xxxxxxxxxxxxxxxx > > http://lists.linaro.org/mailman/listinfo/linaro-kernel > > -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
