linux-kernel - Re: [PATCH] dt-bindings: input: Goodix SPI HID Touchscreen

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Message-ID: <ZxMc-HP8o_qHKhKI@ux-UP-WHL01>
Date: Sat, 19 Oct 2024 10:46:21 +0800
From: Charles Wang <charles.goodix@...il.com>
To: Krzysztof Kozlowski <krzk@...nel.org>, dmitry.torokhov@...il.com,
	hbarnor@...omium.org, dianders@...omium.org,
	conor.dooley@...rochip.com
Cc: jikos@...nel.org, bentiss@...nel.org, linux-input@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dt-bindings: input: Goodix SPI HID Touchscreen

Hi Krzysztof,

On Fri, Oct 18, 2024 at 01:41:41PM +0200, Krzysztof Kozlowski wrote:
> On 18/10/2024 13:18, Charles Wang wrote:
> > 
> > On Fri, Oct 18, 2024 at 07:59:46AM +0200, Krzysztof Kozlowski wrote:
> >> On 18/10/2024 04:08, Charles Wang wrote:
> >>> The Goodix GT7986U touch controller report touch data according to the
> >>> HID protocol through the SPI bus. However, it is incompatible with
> >>> Microsoft's HID-over-SPI protocol.
> >>>
> >>> Signed-off-by: Charles Wang <charles.goodix@...il.com>
> >>> ---
> >>>  .../bindings/input/goodix,gt7375p.yaml        | 68 ++++++++++++++++---
> >>>  1 file changed, 58 insertions(+), 10 deletions(-)
> >>>
> >>> diff --git a/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml b/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml
> >>> index 358cb8275..184d9c320 100644
> >>> --- a/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml
> >>> +++ b/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml
> >>> @@ -8,27 +8,27 @@ title: Goodix GT7375P touchscreen
> >>>  
> >>>  maintainers:
> >>>    - Douglas Anderson <dianders@...omium.org>
> >>> +  - Charles Wang <charles.goodix@...il.com>
> >>>  
> >>>  description:
> >>> -  Supports the Goodix GT7375P touchscreen.
> >>> -  This touchscreen uses the i2c-hid protocol but has some non-standard
> >>> -  power sequencing required.
> >>> -
> >>> -allOf:
> >>> -  - $ref: /schemas/input/touchscreen/touchscreen.yaml#
> >>> +  The Goodix GT7375P and GT7986U touchscreens support both SPI and I2C interfaces.
> >>> +  With the I2C interface, they use the i2c-hid protocol but require non-standard
> >>> +  power sequencing. With the SPI interface, they use a custom HID protocol that
> >>> +  is incompatible with Microsoft's HID-over-SPI protocol.
> >>>  
> >>>  properties:
> >>>    compatible:
> >>>      oneOf:
> >>> -      - const: goodix,gt7375p
> >>> +      - items:
> >>> +          - const: goodix,gt7375p
> >>
> >> That's not a necessary change. Keep old code here.
> >>
> > 
> > Ack,
> > 
> >>>        - items:
> >>>            - const: goodix,gt7986u
> >>>            - const: goodix,gt7375p
> >>> +      - items:
> >>> +          - const: goodix,gt7986u
> >>
> >> Hm? This does not make much sense. Device either is or is not compatible
> >> with gt7375p. Cannot be both.
> >>
> > 
> > Ack,
> > 
> >>>  
> >>>    reg:
> >>> -    enum:
> >>> -      - 0x5d
> >>> -      - 0x14
> >>> +    maxItems: 1
> >>>  
> >>>    interrupts:
> >>>      maxItems: 1
> >>> @@ -57,6 +57,15 @@ properties:
> >>>        This property is used to avoid the back-powering issue.
> >>>      type: boolean
> >>>  
> >>> +  goodix,hid-report-addr:
> >>> +    $ref: /schemas/types.yaml#/definitions/uint32
> >>> +    description:
> >>> +      The register address for retrieving HID report data.
> >>> +      This address is related to the device firmware and may
> >>> +      change after a firmware update.
> >>

> How is this supposed to work? DTS will stay fixed, you cannot change it
> just because firmware changed. User loads new firmware with different
> address, but DTS will have to use old address - so broken property.
>

Sorry for missing this issue in my previous response.
Honestly, although the likelihood of this address changing is low, it is
indeed possible for it to change due to a firmware update during the factory
debugging phase. However, for machines that users have, we will ensure that
this address will not be altered as a result of a firmware upgrade.

> >>> +
> >>> +  spi-max-frequency: true
> >>
> >> Drop
> >>
> > 
> > Ack,
> > 
> >>> +
> >>>  required:
> >>>    - compatible
> >>>    - reg
> >>> @@ -64,6 +73,25 @@ required:
> >>>    - reset-gpios
> >>>    - vdd-supply
> >>>  
> >>> +allOf:
> >>> +  - $ref: /schemas/input/touchscreen/touchscreen.yaml#
> >>> +  - $ref: /schemas/spi/spi-peripheral-props.yaml#
> >>> +
> >>> +  - if:
> >>> +      properties:
> >>> +        compatible:
> >>> +          items:
> >>> +            - const: goodix,gt7986u
> >>> +    then:
> >>> +      required:
> >>> +        - goodix,hid-report-addr
> >>> +    else:
> >>> +      properties:
> >>> +        goodix,hid-report-addr: false
> >>> +        spi-max-frequency: false
> >>
> >> Why? GT7375P also supports SPI.
> >>
> > 
> > No, only GT7986U support SPI. What I'm trying to express here is that
> 
> Description earlier said:
> "The Goodix GT7375P and GT7986U touchscreens support both SPI and I2C
> interfaces."
> 
> so both support?
> 

Sorry, there is an error in the description. Currently, only the GT7986U
supports SPI, I will change the description.

>
> > the GT7375P does not support the properties 'goodix,hid-report-addr'
> > and 'spi-max-frequency. Is there any issue with writing it this way?
> 
> spi-max-frequency could stay, assuming device does not support SPI.
> 

Ack,

Best regards,
Charles