Re: [PATCH] PM: EM: Rank boost and non-boost frequencies separately

[Lukasz Luba]

Hi Guo

On 11/3/26 07:16, Guo Chen wrote:
> On 11/2/2026 11:28 PM, Lukasz Luba wrote:
> > On 10/30/26 08:10, Guo Chen wrote:
> > > em_compute_costs() ranks all the frequencies of the table, boost ones
> > > included. A non-boost frequency can be marked inefficient only because
> > > a faster boost frequency has a lower or equal cost, e.g.
> > >
> > >    3.9 GHz  4.0 GHz (cost C)  4.1 GHz (boost, cost C)

[snip]

> > > +        bool boost = table[i].frequency > max_nonboost;
> > > +
> > > +        if (boost != prev_boost) {
> >
> > We expect in EM fwk that the frequencies are sorted ascending
> > and we return error during setup if the driver callback fails
> > to provide that.
> > Therefore, in this code we don't have to deal with random
> > 'boost' labels with gaps between.
> Hi Lukasz,
>
> Thanks for the review.
>
> You are right. The boundary is derived from the highest non-boost
> frequency, so with an ascending table the boost states always form a
> contiguous top segment, and prev_boost is redundant.
>
> > Let's make all OPPs which are 'boost' equally possible
> > to reach (at least in theory), so label them as
> > 'efficient'. I think this is fair in 'boosting' case scenario
> > and energy has not that importance in it.
> >
> > So simply something like, would be enough IMHO:
> >
> > if (boost)
> >     prev_cost = ULONG_MAX;
> Agreed, this is simpler and gives the same result for the non-boost
> states. Boost states are no longer compared with each other, which is
> also a sensible semantic. I will drop prev_boost and use the above in v2.

Cool, please make sure in your new implementation for the
corner case with the first non-boost OPP from top to be marked as
efficient (you can even force that).

Regards,
Lukasz

> Thanks,
> Guo