linux-kernel - Re: [PATCH v6 2/3] dt-bindings: input: Add TouchNetix axiom touchscreen

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Message-ID: <20240131090652.GB3004909@kb-xps>
Date: Wed, 31 Jan 2024 10:06:52 +0100
From: Kamel Bouhara <kamel.bouhara@...tlin.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc: Rob Herring <robh@...nel.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Henrik Rydberg <rydberg@...math.org>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	Marco Felsch <m.felsch@...gutronix.de>,
	Jeff LaBundy <jeff@...undy.com>,
	catalin.popescu@...ca-geosystems.com,
	mark.satterthwaite@...chnetix.com,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	Gregory Clement <gregory.clement@...tlin.com>,
	bsp-development.geo@...ca-geosystems.com
Subject: Re: [PATCH v6 2/3] dt-bindings: input: Add TouchNetix axiom
 touchscreen

Hello,

On Wed, Jan 31, 2024 at 08:28:43AM +0100, Krzysztof Kozlowski wrote:
> On 30/01/2024 23:28, Rob Herring wrote:
> > On Fri, Jan 26, 2024 at 12:46:16PM +0100, Krzysztof Kozlowski wrote:
> >> On 25/01/2024 17:58, Kamel Bouhara wrote:
> >>> +  reset-gpios:
> >>> +    maxItems: 1
> >>> +
> >>> +  vdda-supply:
> >>> +    description: Analog power supply regulator on VDDA pin
> >>> +
> >>> +  vddi-supply:
> >>> +    description: I/O power supply regulator on VDDI pin
> >>> +
> >>> +  startup-time-ms:
> >>> +    description: delay after power supply regulator is applied in ms
> >>
> >> That's a regulator property - ramp up time.
> >
> > I'm sure there's an existing property name that could be used.
> >
> > But why is it needed? Is it variable per board with the same device? If
> > not, it should be implied by the compatible.
>
> I meant, that regulators have such property. Unless this is coming from
> the device needs, not from the regulator?
>

After looking again into the device's datasheet [1], the delay (startup
time) is not really optional and it shouldn't be set through devicetree.

IIUC, it have to be set unconditionally after a device reset or
a vdda assertion.

[1]: https://www.touchnetix.com/media/dgnjohor/tnxd00394-a3-axiom_ax54a_2d_touch_controller_datasheet.pdf
--
Kamel Bouhara, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com