Re: [PATCH v1 1/2] Revert "dt-bindings:drm/bridge:anx7625:add vendor define"

[Rob Herring <robh@kernel.org>]

On Mon, Mar 7, 2022 at 11:11 AM Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> On Mon, Mar 07, 2022 at 05:57:47PM +0100, Robert Foss wrote:
> > On Mon, 7 Mar 2022 at 17:38, Rob Herring <robh@kernel.org> wrote:
> > >
> > > On Mon, Mar 07, 2022 at 04:45:57PM +0100, Robert Foss wrote:
> > > > This reverts commit a43661e7e819b100e1f833a35018560a1d9abb39.
> > >
> > > S-o-b and reason for the revert?
> > >
> > > > ---
> > > >  .../display/bridge/analogix,anx7625.yaml      | 65 +------------------
> > > >  1 file changed, 2 insertions(+), 63 deletions(-)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/display/bridge/analogix,anx7625.yaml b/Documentation/devicetree/bindings/display/bridge/analogix,anx7625.yaml
> > > > index 1d3e88daca041..ab48ab2f4240d 100644
> > > > --- a/Documentation/devicetree/bindings/display/bridge/analogix,anx7625.yaml
> > > > +++ b/Documentation/devicetree/bindings/display/bridge/analogix,anx7625.yaml
> > > > @@ -43,70 +43,14 @@ properties:
> > > >    vdd33-supply:
> > > >      description: Regulator that provides the supply 3.3V power.
> > > >
> > > > -  analogix,lane0-swing:
> > > > -    $ref: /schemas/types.yaml#/definitions/uint8-array
> > > > -    minItems: 1
> > > > -    maxItems: 20
> > > > -    description:
> > > > -      an array of swing register setting for DP tx lane0 PHY.
> > > > -      Registers 0~9 are Swing0_Pre0, Swing1_Pre0, Swing2_Pre0,
> > > > -      Swing3_Pre0, Swing0_Pre1, Swing1_Pre1, Swing2_Pre1, Swing0_Pre2,
> > > > -      Swing1_Pre2, Swing0_Pre3, they are for [Boost control] and
> > > > -      [Swing control] setting.
> > > > -      Registers 0~9, bit 3:0 is [Boost control], these bits control
> > > > -      post cursor manual, increase the [Boost control] to increase
> > > > -      Pre-emphasis value.
> > > > -      Registers 0~9, bit 6:4 is [Swing control], these bits control
> > > > -      swing manual, increase [Swing control] setting to add Vp-p value
> > > > -      for each Swing, Pre.
> > > > -      Registers 10~19 are Swing0_Pre0, Swing1_Pre0, Swing2_Pre0,
> > > > -      Swing3_Pre0, Swing0_Pre1, Swing1_Pre1, Swing2_Pre1, Swing0_Pre2,
> > > > -      Swing1_Pre2, Swing0_Pre3, they are for [R select control] and
> > > > -      [R Termination control] setting.
> > > > -      Registers 10~19, bit 4:0 is [R select control], these bits are
> > > > -      compensation manual, increase it can enhance IO driven strength
> > > > -      and Vp-p.
> > > > -      Registers 10~19, bit 5:6 is [R termination control], these bits
> > > > -      adjust 50ohm impedance of DP tx termination. 00:55 ohm,
> > > > -      01:50 ohm(default), 10:45 ohm, 11:40 ohm.
> > > > -
> > > > -  analogix,lane1-swing:
> > > > -    $ref: /schemas/types.yaml#/definitions/uint8-array
> > > > -    minItems: 1
> > > > -    maxItems: 20
> > > > -    description:
> > > > -      an array of swing register setting for DP tx lane1 PHY.
> > > > -      DP TX lane1 swing register setting same with lane0
> > > > -      swing, please refer lane0-swing property description.
> > >
> > > These apply to the DP side, so no need to revert this part.
> >
> > Ack.
> >
> > >
> > > > -
> > > > -  analogix,audio-enable:
> > > > -    type: boolean
> > > > -    description: let the driver enable audio HDMI codec function or not.
> > > > -
> > >
> > > Not sure on this one...
> >
> > These additions are independent from my reading of this, would you
> > like a v2 with only the bus-type related changes reverted?

Yes.

> >
> > >
> > > >    ports:
> > > >      $ref: /schemas/graph.yaml#/properties/ports
> > > >
> > > >      properties:
> > > >        port@0:
> > > > -        $ref: /schemas/graph.yaml#/$defs/port-base
> > > > -        unevaluatedProperties: false
> > > > +        $ref: /schemas/graph.yaml#/properties/port
> > > >          description:
> > > > -          MIPI DSI/DPI input.
> > > > -
> > > > -        properties:
> > > > -          endpoint:
> > > > -            $ref: /schemas/media/video-interfaces.yaml#
> > > > -            type: object
> > > > -            additionalProperties: false
> > > > -
> > > > -            properties:
> > > > -              remote-endpoint: true
> > > > -
> > > > -              bus-type:
> > > > -                enum: [1, 5]
> > >
> > > I think the error here is really 1 should be 4 which corresponds to
> > > D-PHY which is used by both CSI and DSI. Otherwise, I don't really see
> > > the issue with bus-type being shared between CSI and DSI.
> >
> > I think that would be a correct solution. And ignoring everything
> > else, the range of this property is something that should be fixed.
> >
> > But that would mean that CPI (camera parallel interface) and DPI
> > (display parallel interface) would share the
> > V4L2_FWNODE_BUS_TYPE_PARALLEL enum. I think that would be perfectly
> > functional, but it is not what V4L2_FWNODE_BUS_TYPE_PARALLEL is
> > documented to represent. As far as I can see it's only intended to
> > represent CPI.
>
> Are you aware of any standard documenting camera parallel interfaces
> with separate sync signals ? I was looking for that the other day, and
> couldn't find much. CPI seems to be an old MIPI standard, but I couldn't
> find any public document, I'not not sure if it actually matches.

I don't recall. Generally, I think the camera side is not quite the
mess the display side is with all the formats.

> Another common parallel interface in SoCs is AXI4 Stream, which we will
> likely need a bus type for. We'll then have to decide on how to handle
> on-SoC custom parallel buses.

Except for those maybe.

> > Instead of having V4L2_FWNODE_BUS_TYPE_PARALLEL represent two
> > standards, I think they should be split. And possibly
> > V4L2_FWNODE_BUS_TYPE_PARALLEL should be renamed for CPI, but that is a
> > separate story. This would provide for the neatest and most legible
> > solution. If this solution is implemented, this range would be
> > incorrect. Additionally the snippet reverted in 2/2 of this series
> > would no longer be valid.
> >
> > As it stands V4L2_FWNODE_BUS_TYPE_PARALLEL was used to represent DPI
> > due to not being caught in the review process.
>
> We may end up using those values, but I think it should be discussed and
> not rushed in v5.17 if possible.

Given it's not actually used (correctly), agreed.

Rob