Re: [PATCH 09/16] dt-bindings: firmware: arm,scmi: Extend bindings for protocol@13

[Rob Herring]

On Thu, Jun 15, 2023 at 3:11 AM Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
>
> On Thu, 15 Jun 2023 at 01:00, Rob Herring <robh@xxxxxxxxxx> wrote:
> >
> > On Wed, Jun 07, 2023 at 02:46:21PM +0200, Ulf Hansson wrote:
> > > The protocol@13 node is describing the performance scaling option for the
> > > ARM SCMI interface, as a clock provider. This is unnecessary limiting, as
> > > performance scaling is in many cases not limited to switching a clock's
> > > frequency.
> > >
> > > Therefore, let's extend the binding so the interface can be modelled as a
> > > generic "performance domain" too. The common way to describe this, is to
> > > use the "power-domain" bindings, so let's use that.
> >
> > What's wrong with the performance-domain binding?
>
> In my opinion I think the performance-domain binding is superfluous.
> We already have plenty of power-domains that do performance scaling
> too - and they stick with the power-domain binding, as it's
> sufficient.

IMO, power-domains should be for power islands which can be power
gated. I know they are abused though. Of course, when things are
hidden in firmware, you don't really know. A power-domain could be
just a clock or a clock could be multiple physical clocks.

> That said, I would rather follow the defacto standard that has been
> used for many years in the kernel. Do you have a preference that we
> should stick to?

If power-domains are sufficient, then why do we have
performance-domains? We need clear rules for when to use what.

Rob