Re: [PATCH v9 2/8] dt-bindings: Introduce interconnect binding

Sudeep Holla
2018-10-03T09:33:46Z

On Tue, Oct 02, 2018 at 11:56:56AM -0700, Saravana Kannan wrote:
>
> On 10/02/2018 04:17 AM, Sudeep Holla wrote:

[...]

> > Yes, I do understand I have made the same point multiple time and it's
> > intentional. We need to get the fragmented f/w support story fixed.
> > Different ARM vendors are doing different things in f/w and ARM sees the
> > same fragmentation story as before. We have come up with new specification
> > and my annoying multiple emails are just to constantly remind the same.
> >
> > I do understand we have existing implementations to consider, but fixing
> > the functionality in arbitrary way is not a good design and it better
> > to get them fixed for future.
>
> I believe the fragmentation you are referring to is  in the
> interface/communication protocol. I see the benefit of standardizing that as
> long as the standard actually turns out to be good. But that's completely
> separate from what the FW can/can't do. Asking to standardize what the FW
> can/can't do doesn't seem realistic as each chip vendor will have different
> priorities - power, performance, cost, chip area, etc. It's the conflation
> of these separate topics that doesn't help IMHO.

I agree on interface/communication protocol fragmentation and firmware
can implement whatever the vendor wish. What I was also referring was
the mix-n-match approach which should be avoided.

e.g. Device A and B's PM is managed completely by firmware using OSPM hints
Suppose Device X's PM is dependent on Device A and B, in which case it's
simpler and cleaner to leave Device X PM to firmware. Reading the state
of A and B and using that as hint for X is just overhead which firmware
can manage better. That was my main concern here: A=CPU and B=some other
device and X is inter-connect to which A and B are connected.

If CPU OPPs are obtained from f/w and this inter-connect from DT, mapping
then is a mess and that's what I was concerned. I am sorry if that's not
the scenario here, I may have mistaken then.

--
Regards,
Sudeep