linux-kernel - Re: [PATCH v4 4/6] dt-bindings: touchscreen: fsl,imx6ul-tsc: support glitch thresold

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Message-ID: <aMrc0GhVbpI38t3L@lizhi-Precision-Tower-5810>
Date: Wed, 17 Sep 2025 12:07:44 -0400
From: Frank Li <Frank.li@....com>
To: Dario Binacchi <dario.binacchi@...rulasolutions.com>
Cc: linux-kernel@...r.kernel.org, linux-amarula@...rulasolutions.com,
	Conor Dooley <conor+dt@...nel.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Fabio Estevam <festevam@...il.com>, Haibo Chen <haibo.chen@....com>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Rob Herring <robh@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Shawn Guo <shawnguo@...nel.org>, devicetree@...r.kernel.org,
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	linux-input@...r.kernel.org
Subject: Re: [PATCH v4 4/6] dt-bindings: touchscreen: fsl,imx6ul-tsc: support
 glitch thresold

On Wed, Sep 17, 2025 at 10:05:09AM +0200, Dario Binacchi wrote:
> Support the touchscreen-glitch-threshold-ns property.
>
> Drivers must convert this value to IPG clock cycles and map it to one of

binding descript hardware, not drivers. So below sentence should be better.

"TSC only supports the four discrete thresholds, counted by IPG clock cycles.
See SC_DEBUG_MODE2 register."

> the four discrete thresholds exposed by the TSC_DEBUG_MODE2 register:
>
>   0: 8191 IPG cycles
>   1: 4095 IPG cycles
>   2: 2047 IPG cycles
>   3: 1023 IPG cycles
>
> Signed-off-by: Dario Binacchi <dario.binacchi@...rulasolutions.com>
>
> ---
>
> Changes in v4:
> - Adjust property description following the suggestions of
>   Conor Dooley and Frank Li.
> - Update the commit description.
>
> Changes in v3:
> - Remove the final part of the description that refers to
>   implementation details.
>
>  .../bindings/input/touchscreen/fsl,imx6ul-tsc.yaml | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/input/touchscreen/fsl,imx6ul-tsc.yaml b/Documentation/devicetree/bindings/input/touchscreen/fsl,imx6ul-tsc.yaml
> index 678756ad0f92..1975f741cf3d 100644
> --- a/Documentation/devicetree/bindings/input/touchscreen/fsl,imx6ul-tsc.yaml
> +++ b/Documentation/devicetree/bindings/input/touchscreen/fsl,imx6ul-tsc.yaml
> @@ -62,6 +62,20 @@ properties:
>      description: Number of data samples which are averaged for each read.
>      enum: [ 1, 4, 8, 16, 32 ]
>
> +  touchscreen-glitch-threshold-ns:
> +    description: |
> +      Minimum duration in nanoseconds a signal must remain stable
> +      to be considered valid.
> +
> +      Drivers must convert this value to IPG clock cycles and map
> +      it to one of the four discrete thresholds exposed by the
> +      TSC_DEBUG_MODE2 register:

same as commit messsage, talk about hardware.

> +
> +        0: 8191 IPG cycles
> +        1: 4095 IPG cycles
> +        2: 2047 IPG cycles
> +        3: 1023 IPG cycles
> +

This case genenerally need enum 4 values, but it relates IPG frequency.
I have not idea how to restrict it base on clk frequency. May DT mainatainer
have idea.

Frank

>  required:
>    - compatible
>    - reg
> --
> 2.43.0
>