On 17-06-19, 09:37, Rajendra Nayak wrote: > > > 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? diff --git a/drivers/opp/core.c b/drivers/opp/core.c index 0fbc77f05048..bae94bfa1e96 100644 --- a/drivers/opp/core.c +++ b/drivers/opp/core.c @@ -751,8 +751,11 @@ static int _set_required_opps(struct device *dev, * @dev: device for which we do this operation * @target_freq: frequency to achieve * - * This configures the power-supplies and clock source to the levels specified - * by the OPP corresponding to the target_freq. + * This configures the power-supplies to the levels specified by the OPP + * corresponding to the target_freq, and programs the clock to a value <= + * target_freq, as rounded by clk_round_rate(). Device wanting to run at fmax + * provided by the opp, should have already rounded to the target OPP's + * frequency. */ -- viresh
