Re: [PATCH v2 12/17] PM: EM: Add argument to get_cost() for runtime modification

[Lukasz Luba]

On 5/30/23 10:53, Dietmar Eggemann wrote:
> On 12/05/2023 11:57, Lukasz Luba wrote:
> > The Energy Model (EM) supports runtime modifications. Let also the
> > artificial EM use this new feature and allow to update the 'cost' values
> > at runtime. When the artificial EM is used there is a need to provide
> > two callbacks: get_cost() and update_power(), not only the last one.
> >
> > Update also CPPC driver code, since the new argument is needed there
> > to compile properly and register EM.
>
> Is there a real use case behind this? It can't be mobile which IMHO
> drivers the rest of the 'Runtime modifiable EM' feature.

Correct, CPPC+EM is not for mobile phones, but notebooks. For now
the notebooks are not tested with that feature and were not in
requirement scope.

> Do we know of any machine using the artificial EM. And do they care
> about EM matching workload or static power?
>
> [...]

For now we don't know about such notebook which uses CPPC + EM
and if it's a candidate for this feature.

I thought, since it's just one patch w/ small change, it would be
consistent to not 'forget' about that notebooks angle. I know
that there are some folks who 'run'/'are willing to run' Arm laptop with
CPPC w/ artificial EM. They might pick that feature as well.