linux-kernel - Re: [PATCH v3 2/4] dt-bindings: display: ti: Add schema for AM625 OLDI Transmitter

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Message-ID: <0144d9b4-e830-44b0-95cd-4d49d5051155@kernel.org>
Date: Sun, 21 Jul 2024 17:36:48 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Aradhya Bhatia <a-bhatia1@...com>,
 Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
 Jyri Sarha <jyri.sarha@....fi>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>
Cc: DRI Development List <dri-devel@...ts.freedesktop.org>,
 Devicetree List <devicetree@...r.kernel.org>,
 Linux Kernel List <linux-kernel@...r.kernel.org>, Nishanth Menon
 <nm@...com>, Vignesh Raghavendra <vigneshr@...com>,
 Praneeth Bajjuri <praneeth@...com>, Udit Kumar <u-kumar1@...com>,
 Francesco Dolcini <francesco@...cini.it>,
 Alexander Sverdlin <alexander.sverdlin@...mens.com>,
 Randolph Sapp <rs@...com>, Devarsh Thakkar <devarsht@...com>,
 Jayesh Choudhary <j-choudhary@...com>, Jai Luthra <j-luthra@...com>
Subject: Re: [PATCH v3 2/4] dt-bindings: display: ti: Add schema for AM625
 OLDI Transmitter

On 16/07/2024 10:42, Aradhya Bhatia wrote:
> The OLDI (transmitters) TXes do not have registers of their own, and are
> dependent on the source video-ports from the DSS to provide
> configuration data. This hardware doesn't directly sit on the internal
> bus of the SoC, but does so via the DSS. Hence, the OLDI TXes are
> supposed to be child nodes under the DSS, and not independent devices.
> 
> Two of the OLDI TXes can function in tandem to output dual-link OLDI
> output, or cloned single-link outputs. In these cases, one OLDI will be
> the primary OLDI, and the other one, a companion.
> 
> The OLDI functionality is further supported by a system-control module,
> which contains a few registers to control OLDI IO power and
> characteristics.
> 
> Add devicetree binding schema for AM625 OLDI TXes.
> 
> Signed-off-by: Aradhya Bhatia <a-bhatia1@...com>
> ---
>  .../bindings/display/ti/ti,am625-oldi.yaml    | 153 ++++++++++++++++++
>  MAINTAINERS                                   |   1 +
>  2 files changed, 154 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/display/ti/ti,am625-oldi.yaml
> 
> diff --git a/Documentation/devicetree/bindings/display/ti/ti,am625-oldi.yaml b/Documentation/devicetree/bindings/display/ti/ti,am625-oldi.yaml
> new file mode 100644
> index 000000000000..0a96e600bc0b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/ti/ti,am625-oldi.yaml
> @@ -0,0 +1,153 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/display/ti/ti,am625-oldi.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Texas Instruments AM625 OLDI Transmitter
> +
> +maintainers:
> +  - Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
> +  - Aradhya Bhatia <a-bhatia1@...com>
> +
> +description: |

Do not need '|' unless you need to preserve formatting.

> +  The AM625 TI Keystone OpenLDI transmitter (OLDI TX) supports serialized RGB
> +  pixel data transmission between host and flat panel display over LVDS (Low
> +  Voltage Differential Sampling) interface. The OLDI TX consists of 7-to-1 data
> +  serializers, and 4-data and 1-clock LVDS outputs. It supports the LVDS output
> +  formats "jeida-18", "jeida-24" and "vesa-18", and can accept 24-bit RGB or
> +  padded and un-padded 18-bit RGB bus formats as input.
> +
> +properties:
> +  reg:
> +    maxItems: 1
> +

How does it even work without compatible? How is this schema selected?
If by part of your next patch, then this is not a proper split - this
patch itself is noop. Squash the patches.

> +  clocks:
> +    maxItems: 1
> +    description: serial clock input for the OLDI transmitters
> +
> +  clock-names:
> +    const: s_clk

Drop _clk or name it correctly.

> +
> +  ti,companion-oldi:
> +    $ref: /schemas/types.yaml#/definitions/phandle
> +    description:
> +      phandle to companion OLDI transmitter. This property is mandatory for the
> +      primarty OLDI TX if the OLDI TXes are expected to work either in dual-lvds
> +      mode or in clone mode. This property should point to the secondary OLDI
> +      TX.
> +
> +  ti,secondary-oldi:
> +    type: boolean
> +    description: Boolean property to mark an OLDI TX as secondary node.

Why? Lack companion tells it, doesn't it?

> +
> +  ti,oldi-io-ctrl:
> +    $ref: /schemas/types.yaml#/definitions/phandle
> +    description:
> +      phandle to syscon device node mapping OLDI IO_CTRL registers found in the
> +      control MMR region. This property is needed for OLDI interface to work.

"This property is needed for OLDI interface to work." tells nothing.
Everything is needed for everything to work. Be specific.


> +
> +  ports:
> +    $ref: /schemas/graph.yaml#/properties/ports
> +
> +    properties:
> +      port@0:
> +        $ref: /schemas/graph.yaml#/properties/port
> +        description: Parallel RGB input port
> +
> +      port@1:
> +        $ref: /schemas/graph.yaml#/properties/port
> +        description: LVDS output port
> +
> +    required:
> +      - port@0
> +      - port@1
> +
> +allOf:
> +  - if:
> +      properties:
> +        ti,secondary-oldi: true

This does not work... Test your schema.

> +    then:
> +      properties:
> +        ti,companion-oldi: false
> +        ti,oldi-io-ctrl: false
> +        clocks: false
> +        clock-names: false
> +
> +    else:
> +      required:
> +        - ti,oldi-io-ctrl
> +        - clocks
> +        - clock-names
> +
> +required:
> +  - reg
> +  - ports
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/soc/ti,sci_pm_domain.h>
> +
> +    oldi_txes {

No underscores in node names.

Node names should be generic. See also an explanation and list of
examples (not exhaustive) in DT specification:
https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html#generic-names-recommendation


> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +        oldi: oldi@0 {
What is the "reg" for?

Best regards,
Krzysztof