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

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Message-ID: <20250916-envelope-depict-7c321fe12341@spud>
Date: Tue, 16 Sep 2025 20:27:08 +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 08:25:53PM +0100, Conor Dooley wrote:
> 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

Or maybe instead of what I did here for the first sentence, yoink the text
from [3/6] instead and re-use it.

> | 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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