Messages in this thread | | | Subject | Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support | From | Sudeep Holla <> | Date | Thu, 13 Jul 2017 13:40:39 +0100 |
| |
On 11/07/17 16:21, Dietmar Eggemann wrote: > On 11/07/17 07:39, Viresh Kumar wrote: >> On 10-07-17, 14:46, Rafael J. Wysocki wrote: >>> This particular change is about a new feature, so making it in the core is OK >>> in two cases IMO: (a) when you actively want everyone to be affected by it and >> >> IMO this change should be done for the whole ARM architecture. And if some >> regression happens due to this, then we come back and solve it. >> >>> (b) when the effect of it on the old systems should not be noticeable. >> >> I am not sure about the effects of this on performance really. >> >> @Dietmar: Any inputs for that ? > > Like I said in the other email, since for (future) > arm/arm64 fast-switch driver, the return value of > cpufreq_driver->fast_switch() does not give us the information that the > frequency value did actually change, we have to implement
I was under the impression that we strictly don't care about that information when I started exploring the fast_switch with the standard firmware interface on ARM platforms(until if and when ARM provides an instruction to achieve that).
If f/w failed to change the frequency, will that be not corrected in the next sample or instance. I would like to know the impact of absence of such notifications.
> arch_set_freq_scale() in the driver. > This means that we probably only implement this in the subset of drivers > which will be used in platforms on which we want to have > frequency-invariant load-tracking. > > A future aperf/mperf like counter FIE solution can give us arch-wide > support when those counters are available. >
Agreed.
-- Regards, Sudeep
| |