linux-kernel - Re: [PATCH v1 1/4] dt-bindings: input: Add Himax HX83102J touchscreen

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Message-ID:
 <TY0PR06MB5611F7123B22C4FDEE319C049E3B2@TY0PR06MB5611.apcprd06.prod.outlook.com>
Date: Thu, 28 Mar 2024 14:05:17 +0800
From: Allen Lin <allencl_lin@...mail.com>
To: Conor Dooley <conor@...nel.org>
Cc: Conor Dooley <conor.dooley@...rochip.com>, Rob Herring <robh@...nel.org>, 
	dmitry.torokhov@...il.com, krzysztof.kozlowski+dt@...aro.org, 
	conor+dt@...nel.org, jikos@...nel.org, benjamin.tissoires@...hat.com, 
	linux-input@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/4] dt-bindings: input: Add Himax HX83102J touchscreen

Conor Dooley <conor@...nel.org> 於 2024年3月28日 週四 上午12:44寫道：
>
> On Wed, Mar 27, 2024 at 03:48:48PM +0800, Allen Lin wrote:
> > Conor Dooley <conor@...nel.org> 於 2024年3月27日 週三 上午3:28寫道：
> > >
> > > On Tue, Mar 26, 2024 at 06:40:28PM +0800, Allen Lin wrote:
> > > > Conor Dooley <conor.dooley@...rochip.com> 於 2024年3月26日 週二 下午4:48寫道：
> > > > >
> > > > > On Tue, Mar 26, 2024 at 01:46:56PM +0800, Allen Lin wrote:
> > > > > > Conor Dooley <conor@...nel.org> 於 2024年3月23日 週六 上午2:34寫道：
> > > > > > >
> > > > > > > On Fri, Mar 22, 2024 at 01:30:09PM -0500, Rob Herring wrote:
> > > > > > > > On Fri, Mar 22, 2024 at 05:54:08PM +0000, Conor Dooley wrote:
> > > > > > > > > On Fri, Mar 22, 2024 at 04:56:03PM +0800, Allen_Lin wrote:
> > > > > > > > > > Add the HX83102j touchscreen device tree bindings documents.
> > > > > > > > > > HX83102j is a Himax TDDI touchscreen controller.
> > > > > > > > > > It's power sequence should be bound with a lcm driver, thus it
> > > > > > > > > > needs to be a panel follower. Others are the same as normal SPI
> > > > > > > > > > touchscreen controller.
> > > > > > > > > >
> > > > > > > > > > Signed-off-by: Allen_Lin <allencl_lin@...mail.com>
> > > > > > > > >
> > > > > > > > > note to self/Krzysztof/Rob:
> > > > > > > > > There was a previous attempt at this kind of device. This version looks
> > > > > > > > > better but might be incomplete given there's a bunch more properties in
> > > > > > > > > that patchset:
> > > > > > > > > https://lore.kernel.org/all/20231017091900.801989-1-tylor_yang@himax.corp-partner.google.com/
> > > > > > > >
> > > > > > > > Those don't look like properties we want coming back.
> > > > > > >
> > > > > > > Oh, I don't want most of them coming back either. There are some
> > > > > > > supplies in there though that I think we would like to come back, no?
> > > > > > > Maybe this particular device doesn't have any supplies, but that doesn't
> > > > > > > really seem credible.
> > > > > >
> > > > > > We will use Firmware-name in Device Tree.
> > > > >
> > > > > > For power supply settings, because there may be other device using
> > > > > > same regulator.
> > > > >
> > > > > If there are other devices using the same regulator is it more
> > > > > important that you document it so that it doesn't get disabled by the
> > > > > other users.
> > > > >
> > > > > > We plan to define it as an optional property for user to control in
> > > > > > next release.
> > > > >
> > > > > I don't see how the regulator would not be required, the device doesn't
> > > > > function without power.
> > > > >
> > > > > Thanks,
> > > > > Conor.
> > > >
> > > > I will set power supply as required.
> > > > The description of power supply as below,
> > > >
> > > > properties:
> > > >   vccd-supply:
> > > >     description: A phandle for the regualtor supplying IO power. Should be own
> > > >                  by TPIC only.
> > >
> > > What does "owned by TPIC" only mean? Why would the vccd supply not be
> > > allowed to be shared with another device?
> > >
> > > > This works for TP digital IO only, main power is
> > > >                  given by display part VSP/VSN power source which is controlled
> > > >                  by lcm driver.
> > >
> > > What drivers control things doesn't really matter here, we're just
> > > describing the hardware. If there's another supply to the controller,
> > > then document it too please.
> > >
> >
> > Below is IC power sequence introduction.
> > https://github.com/HimaxSoftware/Doc/tree/main/Himax_Chipset_Power_Sequence
> >
> > TDDI IC, which means Touch and Display Driver is integrated in one IC,
> > So some power supplies will be controlled by Display driver.
>
> If someone was to turn off the supplies, would the touch component stop
> working? The document says that these supplies must be turned on before
> the touch supplies, so I'm going to assume that both are needed for the
> device to function.
>
> > In yaml Document, can we just list power supplies controlled by touch driver?
>
> If the touch part of this device needs the supplies to function, then
> you need to mention them, regardless of where they're controlled. All we
> are doing in the binding is describing the hardware. What drivers do
> what depends entirely on what software you're using.
>

OK, I will list all supplies required by the driver in the Yaml
document as shown below,

properties:
  compatible:
    const: himax,hx83102j

  reg:
    maxItems: 1

  interrupts:
    maxItems: 1

  reset-gpios:
    maxItems: 1

  vccd-supply:
    description: A phandle for the regualtor supplying IO power.

  vsn-supply:
    description: Negative supply regulator.

  vsp-supply:
    description: Positive supply regulator.

  ddreset-gpios:
    description: A phandle of gpio for display reset controlled by the
LCD driver.

required:
  - compatible
  - reg
  - interrupts
  - reset-gpios
  - panel
  - vccd-supply
  - vsn-supply
  - vsp-supply
  - ddreset-gpios


Thanks,
Allen