Message-ID: <e007ee80-2eff-4859-b2e3-402950081b4f@topic.nl>
Date: Tue, 2 Sep 2025 10:46:05 +0200
From: Mike Looijmans <mike.looijmans@...ic.nl>
To: Krzysztof Kozlowski <krzk@...nel.org>
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 9/2/25 08:53, Krzysztof Kozlowski wrote:
> 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.

reset-gpios fits reasonably. Though the pin is labeled "OE".

(Our experience: The pin must be driven low until the power supplies are 
up. Failure to do so may put the chip in an error state, pulling the I2C 
lines low, that only a power cycle may resolve. So it's close enough to 
"reset")

>> +
>> +  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?

They're exclusive, yes. Will add that.


>> +    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.

Will do.


>
>> +
>> +  ti,slew-rate:
> Common property is "slew-rate" - see pincfg-node.yaml

Will change to slew-rate.


>
>> +    $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?

No, since "adaptive" is the default, I'll just remove that option.


>> +
>> +required:
>> +  - compatible
>> +  - reg
>> +  - ports
>> +
>> +additionalProperties: false
> Best regards,
> Krzysztof
>

-- 
Mike Looijmans

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