Re: [PATCH v8 1/2] dt-bindings: phy: qcom: Add CSI2 C-PHY/DPHY schema

[Vladimir Zapolskiy]

On 6/4/26 03:30, Bryan O'Donoghue wrote:
> On 04/06/2026 01:07, Vladimir Zapolskiy wrote:
> > On 6/4/26 00:18, Bryan O'Donoghue wrote:
> > > On 03/06/2026 21:51, Vladimir Zapolskiy wrote:
> > > > > Actually, one more thing, Why isn't TITAN TOP GDSC here?>>>> +
> > > > If CSIPHYs are true subdevices under the umbrella CAMSS device and well
> > > > described as subnodes, then likely none of power domains are needed
> > > > to be
> > > > repeatedly described in the children device nodes, since this
> > > > information
> > > > can be obtained from the parent device by the driver.
> > > >
> > > > Technically 'power-domains' property can be safely removed, I believe.
> > >
> > > The policy is to describe the power-domain dependency fully since DT
> > > describes hardware not software architecture.
> >
> > It brings no contardiction to the statement I've given above, the needed
> > power domans will be properly described in the parent device, and there
> > is no
> > sense to repeat the properties it again and again in every child subdevice.
> >
> > > Also for a very practical reason a sub-devices can probe/run
> > > asynchronously of the parent device being active so in fact we do need
> > > to describe the PDs fully.
> >
> > In opposite to the above this one is precisely a software centric argument,
> > which should be excluded from the consideration, as well it's not a big
> > deal to make a proper async initialization, removing excessive dt
> > properties
> > is worth it.
>
> Right look forget about that.
>
> - DT requires you to describe your hardware. You're not entitled to have
>     some other device vote for a clock or a PD you rely on.

Above are two uncorrelated between each other sentences.

A device ("consumer") can ask another device ("provider") to behave in
one or another way, this is the only possible and thus natually selected
system design, and nothing behind it was asked. There is no justification
for the proposed flood of multiply repeated data, it's avoidable.

>     That's exactly the type of downstream short cut we are trying to zap.
>
> - In our case we also need to vote on PDs individually when the PHY
>     is active.
>
> In extremis say we are only running the TPG then we have no reason to
> vote for CSIPHY specific rails or operating points in the parent device.

So, TPG shall communicate with CAMSS, there is no CSIPHY in the equation.

> We could make the parent power-domain argument for CAMSS and CCI but we
> have TITAN_TOP_GDSC in CCI specifically because we have to model the
> hardware - including the PDs for that device.

CCI is not described as a child of CAMSS, here the situation is different.

> If tomorrow we put CCI as a sub-device of top-level CAMSS, that won't
> negate the need to include that GDSC.

Of course in this case a phandle to Titan GDSC will be marked as obsolete
or unused for CCI, no problem here.

--
Best wishes,
Vladimir