linux-kernel - Re: [PATCH v4 1/2] dt-bindings: drm/bridge: ti-tmds181: Add TI TMDS181 and SN65DP159 bindings

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Message-ID: <20250902-hasty-spry-nautilus-c05c6a@kuoka>
Date: Tue, 2 Sep 2025 08:53:55 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Mike Looijmans <mike.looijmans@...ic.nl>
Cc: dri-devel@...ts.freedesktop.org, 
	Andrzej Hajda <andrzej.hajda@...el.com>, Conor Dooley <conor+dt@...nel.org>, 
	David Airlie <airlied@...il.com>, Jernej Skrabec <jernej.skrabec@...il.com>, 
	Jonas Karlman <jonas@...boo.se>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Neil Armstrong <neil.armstrong@...aro.org>, 
	Rob Herring <robh@...nel.org>, Robert Foss <rfoss@...nel.org>, Simona Vetter <simona@...ll.ch>, 
	Thomas Zimmermann <tzimmermann@...e.de>, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/2] dt-bindings: drm/bridge: ti-tmds181: Add TI
 TMDS181 and SN65DP159 bindings

On Mon, Sep 01, 2025 at 04:29:01PM +0200, Mike Looijmans wrote:
>  .../bindings/display/bridge/ti,tmds181.yaml   | 152 ++++++++++++++++++
>  1 file changed, 152 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/display/bridge/ti,tmds181.yaml
> 
> diff --git a/Documentation/devicetree/bindings/display/bridge/ti,tmds181.yaml b/Documentation/devicetree/bindings/display/bridge/ti,tmds181.yaml
> new file mode 100644
> index 000000000000..c6387c482431
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/bridge/ti,tmds181.yaml
> @@ -0,0 +1,152 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/display/bridge/ti,tmds181.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: TMDS181 and SN65DP159 HDMI retimer/redriver chips
> +
> +maintainers:
> +  - Mike Looijmans <mike.looijmans@...ic.nl>
> +
> +description: |
> +  Texas Instruments TMDS181 and SN65DP159 retimer and redriver chips.
> +  https://www.ti.com/product/TMDS181
> +  https://www.ti.com/product/SN65DP159
> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - const: ti,tmds181
> +      - items:
> +          - const: ti,sn65dp159
> +          - const: ti,tmds181
> +
> +  reg:
> +    enum:
> +      - 0x5b
> +      - 0x5c
> +      - 0x5d
> +      - 0x5e
> +
> +  oe-gpios:
> +    maxItems: 1
> +    description: GPIO specifier for OE pin (active high).

So that's reset-gpios or powerdown-gpios (see gpio-consumer-common). At
least datasheet calls them that in one place.

> +
> +  vdd-supply:
> +    description: Core power supply, 1.1V
> +
> +  vcc-supply:
> +    description: IO power supply, 3.3V
> +
> +  ports:
> +    $ref: /schemas/graph.yaml#/properties/ports
> +
> +    properties:
> +      port@0:
> +        $ref: /schemas/graph.yaml#/$defs/port-base
> +        unevaluatedProperties: false
> +        description: Video port for HDMI (ish) input
> +
> +        properties:
> +          endpoint:
> +            $ref: /schemas/media/video-interfaces.yaml#
> +            unevaluatedProperties: false
> +
> +      port@1:
> +        $ref: /schemas/graph.yaml#/$defs/port-base
> +        unevaluatedProperties: false
> +        description: Video port for HDMI output (panel or bridge)
> +
> +        properties:
> +          endpoint:
> +            $ref: /schemas/media/video-interfaces.yaml#
> +            unevaluatedProperties: false
> +
> +    required:
> +      - port@0
> +      - port@1
> +
> +  ti,source-mode:
> +    type: boolean
> +    description:
> +      Force chip to operate in "source" mode. Allows to use
> +      a TMDS181 chip (which defaults to sink) as cable driver.
> +
> +  ti,sink-mode:

Aren't these two mutually exclusive? Can same device operate in source
and in sink mode simultaneously?


> +    type: boolean
> +    description:
> +      Force chip to operate in "sink" mode. Allows to use
> +      a DP159 chip (defaults to source) for incoming signals.
> +
> +  ti,retimer-threshold-hz:
> +    minimum: 25000000
> +    maximum: 600000000
> +    default: 200000000
> +    description:
> +      Cross-over point. Up until this pixel clock frequency
> +      the chip remains in the low-power redriver mode. Above
> +      the threshold the chip should operate in retimer mode.
> +
> +  ti,dvi-mode:
> +    type: boolean
> +    description: Makes the DP159 chip operate in DVI mode.

This suggest it is not applicable to TMDS, so you need to restrict it to
disallow it there (see example-schema).

Actually several other properties say they are applicable only to DP159.

> +
> +  ti,slew-rate:

Common property is "slew-rate" - see pincfg-node.yaml

> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    minimum: 0
> +    maximum: 3
> +    default: 3
> +    description: Set slew rate, 0 is slowest, 3 is fastest.
> +
> +  ti,disable-equalizer:
> +    type: boolean
> +    description: Disable the equalizer (to save power).
> +
> +  ti,adaptive-equalizer:
> +    type: boolean
> +    description: Set the equalizer to adaptive mode.

Can equalizer be disabled and adaptive the same time?

> +
> +required:
> +  - compatible
> +  - reg
> +  - ports
> +
> +additionalProperties: false

Best regards,
Krzysztof