Re: [PATCH] PM: EM: Force device drivers to provide power in uW

[Lukasz Luba]

On 3/13/24 19:49, Rafael J. Wysocki wrote:
> On Fri, Mar 8, 2024 at 1:31 PM Lukasz Luba <lukasz.luba@xxxxxxx> wrote:
> > The EM only supports power in uW. Make sure that it is not possible to
> > register some downstream driver which doesn't provide power in uW.
> > The only exception is artificial EM, but that EM is ignored by the rest of
> > kernel frameworks (thermal, powercap, etc).
> >
> > Reported-by: PoShao Chen <poshao.chen@xxxxxxxxxxxx>
> > Signed-off-by: Lukasz Luba <lukasz.luba@xxxxxxx>
> > ---
> >
> > Hi all,
> >
> > The was an issue reported recently that the EM could be used with
> > not aligned drivers which provide milli-Watts. This patch prevents such
> > drivers to register EM (although there are no such in upstream).
> >
> > Regards,
> > Lukasz
> >
> >   kernel/power/energy_model.c | 11 +++++++++++
> >   1 file changed, 11 insertions(+)
> >
> > diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
> > index b686ac0345bd9..9e1c9aa399ea9 100644
> > --- a/kernel/power/energy_model.c
> > +++ b/kernel/power/energy_model.c
> > @@ -612,6 +612,17 @@ int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
> >          else if (cb->get_cost)
> >                  flags |= EM_PERF_DOMAIN_ARTIFICIAL;
> >
> > +       /*
> > +        * EM only supports uW (exception is artificial EM).
> > +        * Therefore, check and force the drivers to provide
> > +        * power in uW.
> > +        */
> > +       if (!microwatts && !(flags & EM_PERF_DOMAIN_ARTIFICIAL)) {
> > +               dev_err(dev, "EM: only supports uW power values\n");
> > +               ret = -EINVAL;
> > +               goto unlock;
> > +       }
> > +
> >          ret = em_create_pd(dev, nr_states, cb, cpus, flags);
> >          if (ret)
> >                  goto unlock;
> > --
>
> Applied as 6.9-rc material, thanks!

Thank you Rafael!