Re: [PATCH v4 3/4] dt-bindings: phy: Add support for QMP phy

[Vivek Gautam]

On 01/20/2017 03:12 AM, Stephen Boyd wrote:
> On 01/19, Vivek Gautam wrote:
> > On 01/19/2017 06:10 AM, Stephen Boyd wrote:
> > > Didn't we already move away from subnodes for lanes in an earlier
> > > revision of these patches? I seem to recall we did that because
> > > lanes are not devices and the whole "phy as a bus" concept not
> > > making sense.
> > Yea, we started out without having any sub-nodes and we
> > argued that we don't require them since the qmp device is
> > represented by the qmp node itself.
> > The lanes otoh are representative of gen_phys and related properties.
> >
> > In the driver -
> > "struct qmp_phy " represents the lanes and holds "struct phy",
> > "struct qcom_qmp" represents the qmp block as a whole and holds
> > "struct device"
> > Does this make lanes qualify to be childs of qmp ?
> Hmm... maybe I was recalling the DSI phy binding. I think there
> are lanes there too but we decided to just have one node.
>
> > "phy as a bus" (just trying to understand here) -
> > let's say a usb phy controller has one HSIC phy port and one USB2 phy port.
> > So, should this phy controller be a bus providing two ports (and so
> > we will have
> > couple of child nodes to the phy controller) ?
> Typically in DT a subnode or collection of subnodes means there's
> some sort of bus involved. Usually each node corresponds to a
> struct device, and the parent node corresponds to the bus or
> controller for the logical bus.
>
> In this case (only PCIe though? not UFS or USB?) it seems like we
> have multiple phys that share a common register space, but
> otherwise they have their own register space and power
> management. Would you have each PCIe controller point to a
> different subnode for their associated phy? I'm trying to
> understand the benefit of the subnodes if they aren't treated as
> struct devices.

AFAIU, It's not straight that forward to point each controller to
different subnodes and not associate a 'struct device' with subnodes.

The phy translation (of_phy_simple_xlate, in case we point each controller
to subnodes) will not be able to associate a correct phy_provider device
to the phy consumer.

Kishon,
Is my understanding correct here? Please correct me if i am missing things.


Regards
Vivek
> At the least, please get DT reviewers to ack the new binding
> before rewriting the code.

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