linux-kernel - Re: [PATCH v5 1/4] dt-bindings: display: bridge: Add schema for Synopsys DW HDMI QP TX IP

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Message-ID: <57wj2vwjv7eehlix2bmvbm3z4agv5fsyp6vmwwqzotkdsadx7n@azqg2kkaeuxz>
Date: Sat, 31 Aug 2024 08:16:26 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
Cc: Andrzej Hajda <andrzej.hajda@...el.com>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>, Jonas Karlman <jonas@...boo.se>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, 
	Sandy Huang <hjc@...k-chips.com>, Heiko Stübner <heiko@...ech.de>, 
	Andy Yan <andy.yan@...k-chips.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Mark Yao <markyao0591@...il.com>, Sascha Hauer <s.hauer@...gutronix.de>, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-rockchip@...ts.infradead.org, devicetree@...r.kernel.org, 
	kernel@...labora.com, Alexandre ARNOUD <aarnoud@...com>, 
	Luis de Arquer <ldearquer@...il.com>
Subject: Re: [PATCH v5 1/4] dt-bindings: display: bridge: Add schema for
 Synopsys DW HDMI QP TX IP

On Sat, Aug 31, 2024 at 12:55:29AM +0300, Cristian Ciocaltea wrote:
> Add dt-binding schema containing the common properties for the Synopsys
> DesignWare HDMI QP TX controller.
> 
> Note this is not a full dt-binding specification, but is meant to be
> referenced by platform-specific bindings for this IP core.
> 
> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
> ---
>  .../display/bridge/synopsys,dw-hdmi-qp.yaml        | 88 ++++++++++++++++++++++
>  1 file changed, 88 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/display/bridge/synopsys,dw-hdmi-qp.yaml b/Documentation/devicetree/bindings/display/bridge/synopsys,dw-hdmi-qp.yaml
> new file mode 100644
> index 000000000000..771f7fba6c50
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/bridge/synopsys,dw-hdmi-qp.yaml
> @@ -0,0 +1,88 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/display/bridge/synopsys,dw-hdmi-qp.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Common Properties for Synopsys DesignWare HDMI QP TX Controller IP
> +
> +maintainers:
> +  - Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
> +
> +description: |
> +  The Synopsys DesignWare HDMI 2.1 Quad-Pixel (QP) TX Controller IP core
> +  supports the following features, among others:
> +
> +  * Fixed Rate Link (FRL)
> +  * Display Stream Compression (DSC)
> +  * 4K@...Hz and 8K@...z video modes
> +  * Variable Refresh Rate (VRR) including Quick Media Switching (QMS)
> +  * Fast Vactive (FVA)
> +  * SCDC I2C DDC access
> +  * Multi-stream audio
> +  * Enhanced Audio Return Channel (EARC)
> +
> +  Note this is not a full dt-binding specification, but is meant to be
> +  referenced by platform-specific bindings for this IP core.
> +
> +properties:
> +  reg:
> +    maxItems: 1
> +
> +  clocks:
> +    minItems: 4
> +    maxItems: 6
> +    items:
> +      - description: Peripheral/APB bus clock
> +      - description: EARC RX biphase clock
> +      - description: Reference clock
> +      - description: Audio interface clock
> +    additionalItems: true

What is the usefulness of all this? How can you even be sure that each
implementation of this core will have exactly these clocks?


> +
> +  clock-names:
> +    minItems: 4
> +    maxItems: 6
> +    items:
> +      - const: pclk
> +      - const: earc
> +      - const: ref
> +      - const: aud
> +    additionalItems: true
> +
> +  interrupts:
> +    minItems: 4
> +    maxItems: 5
> +    items:
> +      - description: AVP Unit interrupt
> +      - description: CEC interrupt
> +      - description: eARC RX interrupt
> +      - description: Main Unit interrupt

If these are real pins, then this seems more possible, but
additionalItems does not make me happy.

I don't see much value in this schema and I am afraid even enforcing
clock and interrupt names won't work for the second or third user.

Best regards,
Krzysztof