Messages in this thread | | | Subject | Re: [RFC v2 01/11] OPP: Don't overwrite rounded clk rate | From | Rajendra Nayak <> | Date | Mon, 17 Jun 2019 09:37:02 +0530 |
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On 6/17/2019 9:20 AM, Viresh Kumar wrote: > On 14-06-19, 10:57, Viresh Kumar wrote: >> Hmm, so this patch won't break anything and I am inclined to apply it again :) >> >> Does anyone see any other issues with it, which I might be missing ? > > I have updated the commit log a bit more to clarify on things, please let me > know if it looks okay. > > opp: Don't overwrite rounded clk rate > > The OPP table normally contains 'fmax' values corresponding to the > voltage or performance levels of each OPP, but we don't necessarily want > all the devices to run at fmax all the time. Running at fmax makes sense > for devices like CPU/GPU, which have a finite amount of work to do and > since a specific amount of energy is consumed at an OPP, its better to > run at the highest possible frequency for that voltage value. > > On the other hand, we have IO devices which need to run at specific > frequencies only for their proper functioning, instead of maximum > possible frequency. > > The OPP core currently roundup to the next possible OPP for a frequency > and select the fmax value. To support the IO devices by the OPP core, > lets do the roundup to fetch the voltage or performance state values, > but not use the OPP frequency value. Rather use the value returned by > clk_round_rate(). > > The current user, cpufreq, of dev_pm_opp_set_rate() already does the > rounding to the next OPP before calling this routine and it won't > have any side affects because of this change.
Looks good to me. Should this also be documented someplace that dev_pm_opp_set_rate() would not be able to distinguish between its users trying to scale CPU/GPU's vs IO devices, so its the callers responsibility to round it accordingly before calling the API?
> > Signed-off-by: Stephen Boyd <swboyd@chromium.org> > Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org> > [ Viresh: Massaged changelog and use temp_opp variable instead ] > Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> > >
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