Re: [PATCH 1/4] media: dt-bindings: Add property to describe CSI-2 C-PHY line orders

["Niklas Söderlund" <niklas.soderlund+renesas@ragnatech.se>]

Hi Sakari,

Tack för din feedback!

On 2024-11-20 08:06:36 +0000, Sakari Ailus wrote:
> Hejssan, Niklas!
> 
> Tack för de här lapparna!
> 
> On Tue, Nov 19, 2024 at 11:12:46PM +0100, Niklas Söderlund wrote:
> > Each data lane on a CSI-2 C-PHY bus uses three phase encoding and is
> > constructed from three physical wires. The wires are referred to as A, B
> > and C and their default order is ABC. However to ease hardware design
> > the specification allows for the wires to be switched in any order.
> > 
> > Add a vendor neutral property to describe the line order used. The
> > property name 'line-orders', the possible values it can be assigned and
> > there names are taken from the MIPI Discovery and Configuration (DisCo)
> > Specification for Imaging.
> > 
> > Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> > ---
> >  .../bindings/media/video-interfaces.yaml      | 20 +++++++++++++++++++
> >  include/dt-bindings/media/video-interfaces.h  |  7 +++++++
> >  2 files changed, 27 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/media/video-interfaces.yaml b/Documentation/devicetree/bindings/media/video-interfaces.yaml
> > index 26e3e7d7c67b..95491e5779ba 100644
> > --- a/Documentation/devicetree/bindings/media/video-interfaces.yaml
> > +++ b/Documentation/devicetree/bindings/media/video-interfaces.yaml
> > @@ -210,6 +210,26 @@ properties:
> >        lane-polarities property is omitted, the value must be interpreted as 0
> >        (normal). This property is valid for serial busses only.
> >  
> > +  line-orders:
> > +    $ref: /schemas/types.yaml#/definitions/uint32-array
> > +    minItems: 1
> > +    maxItems: 8
> > +    enum:
> > +      - 0 # ABC
> > +      - 1 # ACB
> > +      - 2 # BAC
> > +      - 3 # BCA
> > +      - 4 # CAB
> > +      - 5 # CBA
> 
> Do you know hardware documentation using lettes for the lines? I do agree
> it seems less confusing but I've seen only numbers being used.

Yes the R-Car IP core documentation and schematics uses the ABC naming 
for the lines. Unfortunately the documentation is not public.

> 
> > +    description:
> > +      An array of line orders of the CSI-2 C-PHY data lanes. The order of the
> > +      lanes are the same as in data-lanes property. Valid values are 0-5 as
> > +      defined in the MIPI Discovery and Configuration (DisCo) Specification for
> > +      Imaging. The length of the array should be the same length as the
> 
> s/should/must/
> 
> As this is a requirement for DTS authors in particular.
> 
> > +      data-lanes property. If the line-orders property is omitted, the value
> > +      must be interpreted as 0 (ABC). This property is valid for CSI-2 C-PHY
> 
> I would:
> 
> s/must/shall/
> 
> > +      busses only.
> > +
> >    strobe:
> >      $ref: /schemas/types.yaml#/definitions/uint32
> >      enum: [ 0, 1 ]
> > diff --git a/include/dt-bindings/media/video-interfaces.h b/include/dt-bindings/media/video-interfaces.h
> > index 68ac4e05e37f..88b9d05d8075 100644
> > --- a/include/dt-bindings/media/video-interfaces.h
> > +++ b/include/dt-bindings/media/video-interfaces.h
> > @@ -13,4 +13,11 @@
> >  #define MEDIA_BUS_TYPE_PARALLEL			5
> >  #define MEDIA_BUS_TYPE_BT656			6
> >  
> > +#define MEDIA_BUS_CSI2_CPHY_LINE_ORDER_ABC	0
> > +#define MEDIA_BUS_CSI2_CPHY_LINE_ORDER_ACB	1
> > +#define MEDIA_BUS_CSI2_CPHY_LINE_ORDER_BAC	2
> > +#define MEDIA_BUS_CSI2_CPHY_LINE_ORDER_BCA	3
> > +#define MEDIA_BUS_CSI2_CPHY_LINE_ORDER_CAB	4
> > +#define MEDIA_BUS_CSI2_CPHY_LINE_ORDER_CBA	5
> > +
> >  #endif /* __DT_BINDINGS_MEDIA_VIDEO_INTERFACES_H__ */
> 
> -- 
> Med vänliga hälsningar,
> 
> Sakari Ailus

-- 
Kind Regards,
Niklas Söderlund