linux-kernel - Re: [PATCH 02/21] dt-bindings: display: tilcdc: Add fifo-threshold property

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Message-ID: <20251127103745.7c5d55e6@kmaincent-XPS-13-7390>
Date: Thu, 27 Nov 2025 10:37:45 +0100
From: Kory Maincent <kory.maincent@...tlin.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
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>, Rob Herring <robh@...nel.org>, Krzysztof
 Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Russell
 King <linux@...linux.org.uk>, Bartosz Golaszewski <brgl@...ev.pl>, Tony
 Lindgren <tony@...mide.com>, 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>, Markus
 Schneider-Pargmann <msp@...libre.com>, Luca Ceresoli
 <luca.ceresoli@...tlin.com>, Louis Chauvet <louis.chauvet@...tlin.com>,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, Miguel Gazquez
 <miguel.gazquez@...tlin.com>, dri-devel@...ts.freedesktop.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-omap@...r.kernel.org
Subject: Re: [PATCH 02/21] dt-bindings: display: tilcdc: Add fifo-threshold
 property

On Thu, 27 Nov 2025 09:22:56 +0100
Krzysztof Kozlowski <krzk@...nel.org> wrote:

> On Wed, Nov 26, 2025 at 06:35:44PM +0100, Kory Maincent (TI.com) wrote:
> > Add the fifo-threshold property to control the DMA FIFO threshold level,
> > which specifies the number of words that must be loaded before the DMA
> > FIFO becomes ready.
> > 
> > This property is needed to support the da850-evm board configuration
> > which requires a non-default FIFO threshold value. Currently, this value
> > is specified through the deprecated ti,tilcdc,panel binding. Adding this
> > property to the tilcdc binding allows for proper configuration while
> > migrating away from the non-standard panel binding.
> > 
> > The default value is 8 words, with valid values being powers of 2 from
> > 8 to 512.
> > 
> > Related commit: 55da73fa7a68c ("ARM: dts: davinci: da850-evm: Increase
> > fifo threshold")  
> 
> Please use syntax pointed out by checkpatch. The checkpatch error (not
> even a warning) is there for reason, so we can apply filter/grep
> easily.
> 
> > 
> > Signed-off-by: Kory Maincent (TI.com) <kory.maincent@...tlin.com>
> > ---
> >  Documentation/devicetree/bindings/display/tilcdc/tilcdc.yaml | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/display/tilcdc/tilcdc.yaml
> > b/Documentation/devicetree/bindings/display/tilcdc/tilcdc.yaml index
> > 34ac1fd04d5c6..bf6d506e25e17 100644 ---
> > a/Documentation/devicetree/bindings/display/tilcdc/tilcdc.yaml +++
> > b/Documentation/devicetree/bindings/display/tilcdc/tilcdc.yaml @@ -46,6
> > +46,13 @@ properties: The maximum pixel clock that can be supported by the
> > lcd controller in KHz.
> >  
> > +  fifo-threshold:  
> 
> Why this is not deducible from the compatible? Feels like a specific SoC
> issue.

This is indeed deductible from the compatible as ti,da850-tilcdc is only use in
the related devicetree. Thanks for the pointer this will avoid adding a new dt
parameter.

> 
> Anyway, missing vendor prefix
> 
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    enum: [8, 16, 32, 64, 128, 256, 512]
> > +    description:
> > +      Number of words loaded before the DMA fifo becomes ready. The default
> > +      value is 8.  
> 
> missing default and drop free form text in description.
> 
> > +
> >    blue-and-red-wiring:
> >      enum: [straight, crossed]
> >      description:
> > 
> > -- 
> > 2.43.0
> >   



-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com