linux-kernel - Re: [PATCH 1/4] dt-bindings: display: ti,am65x-dss: Add clk property for data edge synchronization

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Message-ID: <20250730235653.GA1914482-robh@kernel.org>
Date: Wed, 30 Jul 2025 18:56:53 -0500
From: Rob Herring <robh@...nel.org>
To: Louis Chauvet <louis.chauvet@...tlin.com>
Cc: Jyri Sarha <jyri.sarha@....fi>,
	Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Sam Ravnborg <sam@...nborg.org>,
	Benoit Parrot <bparrot@...com>, Lee Jones <lee@...nel.org>,
	Nishanth Menon <nm@...com>, Vignesh Raghavendra <vigneshr@...com>,
	Tero Kristo <kristo@...nel.org>, thomas.petazzoni@...tlin.com,
	Jyri Sarha <jsarha@...com>, Tomi Valkeinen <tomi.valkeinen@...com>,
	dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	stable@...r.kernel.org
Subject: Re: [PATCH 1/4] dt-bindings: display: ti,am65x-dss: Add clk property
 for data edge synchronization

On Wed, Jul 30, 2025 at 07:02:44PM +0200, Louis Chauvet wrote:
> The dt-bindings for the display, specifically ti,am65x-dss, need to
> include a clock property for data edge synchronization. The current
> implementation does not correctly apply the data edge sampling property.
> 
> To address this, synchronization of writes to two different registers is
> required: one in the TIDSS IP (which is already described in the tidss
> node) and one is in the Memory Mapped Control Register Modules (added by
> the previous commit).
> 
> As the Memory Mapped Control Register Modules is located in a different
> IP, we need to use a phandle to write values in its registers.

You can always just lookup the target node by compatible. Then you don't 
need a DT update to solve your problem.

> 
> Fixes: 32a1795f57ee ("drm/tidss: New driver for TI Keystone platform Display SubSystem")
> Signed-off-by: Louis Chauvet <louis.chauvet@...tlin.com>
> 
> ---
> 
> Cc: stable@...r.kernel.org
> ---
>  Documentation/devicetree/bindings/display/ti/ti,am65x-dss.yaml | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/display/ti/ti,am65x-dss.yaml b/Documentation/devicetree/bindings/display/ti/ti,am65x-dss.yaml
> index 361e9cae6896c1f4d7fa1ec47a6e3a73bca2b102..b9a373b569170332f671416eb7bbc0c83f7b5ea6 100644
> --- a/Documentation/devicetree/bindings/display/ti/ti,am65x-dss.yaml
> +++ b/Documentation/devicetree/bindings/display/ti/ti,am65x-dss.yaml
> @@ -133,6 +133,12 @@ properties:
>        and OLDI_CLK_IO_CTRL registers. This property is needed for OLDI
>        interface to work.
>  
> +  ti,clk-ctrl:
> +    $ref: /schemas/types.yaml#/definitions/phandle
> +    description:
> +      phandle to syscon device node mapping CFG0_CLK_CTRL registers.
> +      This property is needed for proper data sampling edge.
> +
>    max-memory-bandwidth:
>      $ref: /schemas/types.yaml#/definitions/uint32
>      description:
> 
> -- 
> 2.50.1
>