linux-kernel - Re: [PATCH v3 4/6] dt-bindings: touchscreen: fsl,imx6ul-tsc: support glitch thresold

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Message-ID: <20250916-auction-angelfish-0239691a54e5@spud>
Date: Tue, 16 Sep 2025 20:25:53 +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 v3 4/6] dt-bindings: touchscreen: fsl,imx6ul-tsc: support
 glitch thresold

On Tue, Sep 16, 2025 at 11:55:17AM -0400, Frank Li wrote:
> On Mon, Sep 15, 2025 at 09:53:06PM +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>
> >
> > ---
> >
> > Changes in v3:
> > - Remove the final part of the description that refers to
> >   implementation details.
> >
> >  .../bindings/input/touchscreen/fsl,imx6ul-tsc.yaml   | 12 ++++++++++++
> >  1 file changed, 12 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..6214d8be5a99 100644
> > --- a/Documentation/devicetree/bindings/input/touchscreen/fsl,imx6ul-tsc.yaml
> > +++ b/Documentation/devicetree/bindings/input/touchscreen/fsl,imx6ul-tsc.yaml
> > @@ -62,6 +62,18 @@ 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 have to use ns here. You can caculate in driver to match to closed one.

That is what he is saying it is doing - "internally the value is
converted to IPG clock cycles" and so on. Your repeated misunderstanding
of this though points out that maybe the description is still lacking?

Dario, how about:
| The gitch threshold in nanoseconds. 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:
| 
|         0: 8191 IPG cycles
|         1: 4095 IPG cycles
|         2: 2047 IPG cycles
|         3: 1023 IPG cycles
? 
I dropped the bit about arbitrary values, due to my comment on the other
version a few mins ago.

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