linux-kernel - Re: [PATCH v2 4/6] dt-bindings: touchscreen: fsl,imx6ul-tsc: support glitch thresold

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Message-ID: <20250915-tinker-music-03cff49a41a7@spud>
Date: Mon, 15 Sep 2025 18:42:13 +0100
From: Conor Dooley <conor@...nel.org>
To: Frank Li <Frank.li@....com>
Cc: Dario Binacchi <dario.binacchi@...rulasolutions.com>,
	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 v2 4/6] dt-bindings: touchscreen: fsl,imx6ul-tsc: support
 glitch thresold

On Mon, Sep 15, 2025 at 10:30:26AM -0400, Frank Li wrote:
> On Sun, Sep 14, 2025 at 07:16:01PM +0200, Dario Binacchi wrote:
> > Support the touchscreen-glitch-threshold-ns property. Unlike the
> > generic description in touchscreen.yaml, this controller maps the
> > provided value to one of four discrete thresholds internally.
> >
> > Signed-off-by: Dario Binacchi <dario.binacchi@...rulasolutions.com>
> > ---
> >
> > (no changes since v1)
> >
> >  .../input/touchscreen/fsl,imx6ul-tsc.yaml         | 15 +++++++++++++++
> >  1 file changed, 15 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..310af56a0be6 100644
> > --- a/Documentation/devicetree/bindings/input/touchscreen/fsl,imx6ul-tsc.yaml
> > +++ b/Documentation/devicetree/bindings/input/touchscreen/fsl,imx6ul-tsc.yaml
> > @@ -62,6 +62,21 @@ properties:
> >      description: Number of data samples which are averaged for each read.
> >      enum: [ 1, 4, 8, 16, 32 ]
> >
> > +  touchscreen-glitch-threshold-ns:
> > +    description: |
> > +      Unlike the generic property defined in touchscreen.yaml, this
> > +      controller does not allow arbitrary values. Internally the value is
> > +      converted to IPG clock cycles and mapped to one of 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
> 
> you should use ns
>    enum:
>       - 1023
>       - 2047
>       - 4095
>       - 8191
> 
> you can limit only 4 values, but unit have to ns. your driver map it to
> register value.

Looking at the driver change, I think Dario is already doing that. The
text here is just talking about how the controller doesn't support
anything other than these 4 glitch threshold and mapping must be done in
some way.

> > +
> > +      Any value provided in device tree is converted to cycles and rounded
> > +      up to the next supported threshold, or to 8191 if above 4095.

This seems to be the implementation details of one particular driver,
and does not belong in a binding.

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

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