Re: [V9, 1/2] media: dt-bindings: media: i2c: Document OV02A10 bindings

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Hi Sakari, Rob,

On Thu, 2020-05-28 at 00:16 +0300, Sakari Ailus wrote:
> Hi Rob, Dongchun,
> 
> On Wed, May 27, 2020 at 09:27:22AM -0600, Rob Herring wrote:
> > > > > +    properties:
> > > > > +      endpoint:
> > > > > +        type: object
> > > > > +        additionalProperties: false
> > > > > +
> > > > > +        properties:
> > >
> > > Actually I wonder whether we need to declare 'clock-lanes' here?
> > 
> > Yes, if you are using it.
> 
> Dongchun, can you confirm the chip has a single data and a single clock
> lane and that it does not support lane reordering?
> 

>From the datasheet, 'MIPI inside the OV02A10 provides one single
uni-directional clock lane and one bi-directional data lane solution for
communication links between components inside a mobile device.
The data lane has full support for HS(uni-directional) and
LP(bi-directional) data transfer mode.'

The sensor doesn't support lane reordering, so 'clock-lanes' property
would not be added in next release.

> So if there's nothing to convey to the driver, also the data-lanes should
> be removed IMO.
> 

However, 'data-lanes' property may still be required.
It is known that either data-lanes or clock-lanes is an array of
physical data lane indexes. Position of an entry determines the logical
lane number, while the value of an entry indicates physical lane, e.g.,
for 1-lane MIPI CSI-2 bus we could have "data-lanes = <1>;", assuming
the clock lane is on hardware lane 0.

As mentioned earlier, the OV02A10 sensor supports only 1C1D and does not
support lane reordering, so here we shall use 'data-lanes = <1>' as
there is only a clock lane for OV02A10.

Reminder:
If 'data-lanes' property is not present, the driver would assume
four-lane operation. This means for one-lane or two-lane operation, this
property must be present and set to the right physical lane indexes.
If the hardware does not support lane reordering, monotonically
incremented values shall be used from 0 or 1 onwards, depending on
whether or not there is also a clock lane.





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