Re: [PATCH v3 1/2] dt-bindings: display: bridge: add TI TDP158

[Maxime Ripard <mripard@kernel.org>]

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Hi,

On Thu, Jun 27, 2024 at 01:13:03PM GMT, Marc Gonzalez wrote:
> TDP158 is an AC-coupled DVI / HDMI to TMDS level shifting Redriver.
> It supports DVI 1.0, HDMI 1.4b and 2.0b.
> It supports 4 TMDS channels, HPD, and a DDC interface.
> It supports dual power supply rails (1.1V on VDD, 3.3V on VCC)
> for power reduction. Several methods of power management are
> implemented to reduce overall power consumption.
> It supports fixed receiver EQ gain using I2C or pin strap to
> compensate for different lengths input cable or board traces.
> 
> Features
> 
> - AC-coupled TMDS or DisplayPort dual-mode physical layer input
> to HDMI 2.0b TMDS physical layer output supporting up to 6Gbps
> data rate, compatible with HDMI 2.0b electrical parameters
> - DisplayPort dual-mode standard version 1.1
> - Programmable fixed receiver equalizer up to 15.5dB
> - Global or independent high speed lane control, pre-emphasis
> and transmit swing, and slew rate control
> - I2C or pin strap programmable
> - Configurable as a DisplayPort redriver through I2C
> - Full lane swap on main lanes
> - Low power consumption (200 mW at 6Gbps, 8 mW in shutdown)
> 
> https://www.ti.com/lit/ds/symlink/tdp158.pdf
> 
> Signed-off-by: Marc Gonzalez <mgonzalez@freebox.fr>
> ---
>  .../bindings/display/bridge/ti,tdp158.yaml         | 51 ++++++++++++++++++++++
>  1 file changed, 51 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/display/bridge/ti,tdp158.yaml b/Documentation/devicetree/bindings/display/bridge/ti,tdp158.yaml
> new file mode 100644
> index 0000000000000..21c8585c3bb2d
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/bridge/ti,tdp158.yaml
> @@ -0,0 +1,51 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/display/bridge/ti,tdp158.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: TI TDP158 HDMI to TMDS Redriver
> +
> +maintainers:
> +  - Arnaud Vrac <avrac@freebox.fr>
> +  - Pierre-Hugues Husson <phhusson@freebox.fr>
> +
> +properties:
> +  compatible:
> +    const: ti,tdp158
> +
> +  reg:
> +    description: I2C address of the device
> +
> +  enable-gpios:
> +    description: GPIO controlling bridge enable
> +
> +  vcc-supply:
> +    description: Power supply 3.3V
> +
> +  vdd-supply:
> +    description: Power supply 1.1V
> +
> +  ports:
> +    $ref: /schemas/graph.yaml#/properties/ports
> +
> +    properties:
> +      port@0:
> +        $ref: /schemas/graph.yaml#/properties/port
> +        description: Bridge input
> +
> +      port@1:
> +        $ref: /schemas/graph.yaml#/properties/port
> +        description: Bridge output
> +
> +    required:
> +      - port@0
> +      - port@1

The device supports DVI, HDMI or DP input, with various requirements and
capabilities depending on the input. Your binding doesn't address that.

Similarly, it can do lane-swapping, so we should probably have a
property to describe what mapping we want to use.

The i2c register access (and the whole behaviour of the device) is
constrained on the I2C_EN pin status, and you can't read it from the
device, so it's also something we need to have in the DT.

Maxime

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