linux-kernel - Re: [PATCH v2 8/9] media: dt-bindings: Add Intel Displayport RX IP

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Date: Tue, 27 Feb 2024 08:29:11 -0600
From: Rob Herring <robh@...nel.org>
To: Paweł Anikiel <panikiel@...gle.com>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>, airlied@...il.com,
	akpm@...ux-foundation.org, conor+dt@...nel.org, daniel@...ll.ch,
	dinguyen@...nel.org, hverkuil-cisco@...all.nl,
	krzysztof.kozlowski+dt@...aro.org,
	maarten.lankhorst@...ux.intel.com, mchehab@...nel.org,
	mripard@...nel.org, tzimmermann@...e.de, devicetree@...r.kernel.org,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org, chromeos-krk-upstreaming@...gle.com,
	ribalda@...omium.org
Subject: Re: [PATCH v2 8/9] media: dt-bindings: Add Intel Displayport RX IP

On Mon, Feb 26, 2024 at 11:59:42AM +0100, Paweł Anikiel wrote:
> On Mon, Feb 26, 2024 at 10:13 AM Krzysztof Kozlowski
> <krzysztof.kozlowski@...aro.org> wrote:
> >
> > On 21/02/2024 17:02, Paweł Anikiel wrote:
> > > The Intel Displayport RX IP is a part of the DisplayPort Intel FPGA IP
> > > Core. It implements a DisplayPort 1.4 receiver capable of HBR3 video
> > > capture and Multi-Stream Transport. The user guide can be found here:
> > >
> > > https://www.intel.com/programmable/technical-pdfs/683273.pdf
> > >
> > > Signed-off-by: Paweł Anikiel <panikiel@...gle.com>
> > > ---
> > >  .../devicetree/bindings/media/intel,dprx.yaml | 160 ++++++++++++++++++
> > >  1 file changed, 160 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/media/intel,dprx.yaml
> > >
> > > diff --git a/Documentation/devicetree/bindings/media/intel,dprx.yaml b/Documentation/devicetree/bindings/media/intel,dprx.yaml
> > > new file mode 100644
> > > index 000000000000..31025f2d5dcd
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/media/intel,dprx.yaml
> > > @@ -0,0 +1,160 @@
> > > +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/media/intel,dprx.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Intel DisplayPort RX IP
> > > +
> > > +maintainers:
> > > +  - Paweł Anikiel <panikiel@...gle.com>
> > > +
> > > +description: |
> > > +  The Intel Displayport RX IP is a part of the DisplayPort Intel FPGA IP
> > > +  Core. It implements a DisplayPort 1.4 receiver capable of HBR3 video
> > > +  capture and Multi-Stream Transport.
> > > +
> > > +  The IP features a large number of configuration parameters, found at:
> > > +  https://www.intel.com/content/www/us/en/docs/programmable/683273/23-3-20-0-1/sink-parameters.html
> > > +
> > > +  The following parameters have to be enabled:
> > > +    - Support DisplayPort sink
> > > +    - Enable GPU control
> > > +  The following parameters' values have to be set in the devicetree:
> > > +    - RX maximum link rate
> > > +    - Maximum lane count
> > > +    - Support MST
> > > +    - Max stream count (only if Support MST is enabled)
> > > +
> > > +properties:
> > > +  compatible:
> > > +    const: intel,dprx-20.0.1
> > > +
> > > +  reg:
> > > +    maxItems: 1
> > > +
> > > +  interrupts:
> > > +    maxItems: 1
> > > +
> > > +  intel,max-link-rate:
> > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > +    description: Max link rate configuration parameter
> >
> > Please do not duplicate property name in description. It's useless.
> > Instead explain what is this responsible for.
> >
> > Why max-link-rate would differ for the same dprx-20.0.1? And why
> > standard properties cannot be used?
> >
> > Same for all questions below.
> 
> These four properties are the IP configuration parameters mentioned in
> the device description. When generating the IP core you can set these
> parameters, which could make them differ for the same dprx-20.0.1.
> They are documented in the user guide, for which I also put a link in
> the description. Is that enough? Or should I also document these
> parameters here?

Use the standard properties: link-frequencies and data-lanes. Those go 
under the port(s) because they are inheritly per logical link.

Rob