Re: [PATCH 6/8] dt-bindings: media: nxp,imx-mipi-csi2: Add fsl,num-channels property

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Tue, Jun 10, 2025 at 11:18:29AM +0300, Laurent Pinchart wrote:
> On Mon, Jun 09, 2025 at 03:08:39PM -0400, Frank Li wrote:
> > On Mon, Jun 09, 2025 at 09:20:33PM +0300, Laurent Pinchart wrote:
> > > On Mon, Jun 09, 2025 at 12:53:48PM -0500, Adam Ford wrote:
> > > > On Mon, Jun 9, 2025 at 10:32 AM Frank Li wrote:
> > > > > On Mon, Jun 09, 2025 at 02:58:38AM +0300, Laurent Pinchart wrote:
> > > > > > The CSI-2 receiver can be instantiated with up to four output channels.
> > > > > > This is an integration-specific property, specify the number of
> > > > > > instantiated channels through a new fsl,num-channels property. The
> > > > > > property is optional, and defaults to 1 as only one channel is currently
> > > > > > supported by drivers.
> > > > > >
> > > > > > The only known SoC to have more than one channel is the i.MX8MP. As the
> > > > > > binding examples do not cover that SoC, don't update them.
> > > > > >
> > > > > > Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > > > > > ---
> > > > > >  .../devicetree/bindings/media/nxp,imx-mipi-csi2.yaml       | 7 +++++++
> > > > > >  1 file changed, 7 insertions(+)
> > > > > >
> > > > > > diff --git a/Documentation/devicetree/bindings/media/nxp,imx-mipi-csi2.yaml b/Documentation/devicetree/bindings/media/nxp,imx-mipi-csi2.yaml
> > > > > > index db4889bf881e..41ad5b84eaeb 100644
> > > > > > --- a/Documentation/devicetree/bindings/media/nxp,imx-mipi-csi2.yaml
> > > > > > +++ b/Documentation/devicetree/bindings/media/nxp,imx-mipi-csi2.yaml
> > > > > > @@ -68,6 +68,13 @@ properties:
> > > > > >      default: 166000000
> > > > > >      deprecated: true
> > > > > >
> > > > > > +  fsl,num-channels:
> > > > > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > > > > +    description: Number of output channels
> > > > > > +    minimum: 1
> > > > > > +    maximum: 4
> > > > > > +    default: 1
> > > > > > +
> > > > >
> > > > > Look like it is fixed value for each compabiable string, So it is not
> > > > > suitable for adding new property. It should be in driver data of each
> > > > > compatible strings.
> > > > >
> > > > > I met similar case before. DT team generally don't agree on add such
> > > > > property, unless there are two instances in the same chip, which have
> > > > > difference channel number.
> > > >
> > > > If the DT changes are rejected, can the number of channels be added to
> > > > the data structure inside mipi_csis_of_match?  We have compatibles for
> > > > 8mm and imx7.  If we add an imx8mp compatible we could add a reference
> > > > to the number of channels.
> > >
> > > I thought about it, and decided to add a new property because the number
> > > of channels is really a synthesis time configuration parameter, and
> > > could differ between different CSIS instances in the same SoC.
> > 
> > Need add such information at binding doc's commit message,
> 
> I'll update the commit message.

The commit message in v2 will state

    dt-bindings: media: nxp,imx-mipi-csi2: Add fsl,num-channels property

    The CSI-2 receiver can be instantiated with up to four output channels.
    This is an integration-specific property, specify the number of
    instantiated channels through a new fsl,num-channels property. The
    property is optional, and defaults to 1 as only one channel is currently
    supported by drivers.

    Using the compatible string to infer the number of channels has been
    considered, but multiple instances of the same CSIS in the same SoC
    could conceptually be synthesized with a different number of channels.
    An explicit property is therefore more appropriate.

    The only known SoC to have more than one channel is the i.MX8MP. As the
    binding examples do not cover that SoC, don't update them.

Rob, Krzysztof, Conor, are you fine with adding this property ?

> > ideally provide an example for it.
> 
> That I can't provide because the few SoCs I'm working with do not
> integrate multiple CSIS instances with different parameters.
> 
> > > > > >    ports:
> > > > > >      $ref: /schemas/graph.yaml#/properties/ports
> > > > > >

-- 
Regards,

Laurent Pinchart