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

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Message-ID: <20250916-bonus-wildness-608ec9a83546@spud>
Date: Tue, 16 Sep 2025 19:34:57 +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 Tue, Sep 16, 2025 at 12:03:01PM -0400, Frank Li wrote:
> On Mon, Sep 15, 2025 at 06:42:13PM +0100, Conor Dooley wrote:
> > 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.
> 
> Thanks, but descripton is confused.
> "Unlike the generic property defined in touchscreen.yaml", which let me
> think value is 0..3, instead of ns.
> 
> Suggest Remove
> 
> "Unlike the generic property defined in touchscreen.yaml, this
> controller does not allow arbitrary values"

Yeah, I agree this should be removed. It's unlikely that /any/
touchscreen will support completely arbitrary values, so stating it is
redundant.

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