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

[Lukasz Luba <lukasz.luba@arm.com>]

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