linux-kernel - Re: [PATCH 1/2] dt-bindings: display: simple: support non-default data-mapping

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Date:   Wed, 19 Apr 2023 08:29:54 +0200
From:   Johannes Zink <j.zink@...gutronix.de>
To:     Rob Herring <robh@...nel.org>
Cc:     thierry.reding@...il.com, sam@...nborg.org, airlied@...il.com,
        daniel@...ll.ch, krzysztof.kozlowski+dt@...aro.org,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel@...gutronix.de
Subject: Re: [PATCH 1/2] dt-bindings: display: simple: support non-default
 data-mapping

Hi Rob,

On 4/18/23 23:20, Rob Herring wrote:
> On Fri, Apr 14, 2023 at 06:11:15PM +0200, Johannes Zink wrote:
>> Some Displays support more than just a single default lvds data mapping,
>> which can be used to run displays on only 3 LVDS lanes in the jeida-18
>> data-mapping mode.
>>
>> Add an optional data-mapping property, analogously to panel-lvds, to
>> allow overriding the default data mapping.
>>
>> Signed-off-by: Johannes Zink <j.zink@...gutronix.de>
>> ---
>>   .../bindings/display/panel/panel-simple.yaml  | 51 +++++++++++++++++++
>>   1 file changed, 51 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/display/panel/panel-simple.yaml b/Documentation/devicetree/bindings/display/panel/panel-simple.yaml
>> index 18241f4051d2..6e219f67dd67 100644
>> --- a/Documentation/devicetree/bindings/display/panel/panel-simple.yaml
>> +++ b/Documentation/devicetree/bindings/display/panel/panel-simple.yaml
>> @@ -349,6 +349,57 @@ properties:
>>     power-supply: true
>>     no-hpd: true
>>     hpd-gpios: true
>> +  data-mapping:
>> +    enum:
>> +      - jeida-18
>> +      - jeida-24
>> +      - vesa-24
>> +    description: |
>> +      The color signals mapping order.
>> +
>> +      LVDS data mappings are defined as follows.
>> +
>> +      - "jeida-18" - 18-bit data mapping compatible with the [JEIDA], [LDI] and
>> +        [VESA] specifications. Data are transferred as follows on 3 LVDS lanes.
>> +
>> +      Slot          0       1       2       3       4       5       6
>> +                ________________                         _________________
>> +      Clock                     \_______________________/
>> +                  ______  ______  ______  ______  ______  ______  ______
>> +      DATA0     ><__G0__><__R5__><__R4__><__R3__><__R2__><__R1__><__R0__><
>> +      DATA1     ><__B1__><__B0__><__G5__><__G4__><__G3__><__G2__><__G1__><
>> +      DATA2     ><_CTL2_><_CTL1_><_CTL0_><__B5__><__B4__><__B3__><__B2__><
>> +
>> +      - "jeida-24" - 24-bit data mapping compatible with the [DSIM] and [LDI]
>> +        specifications. Data are transferred as follows on 4 LVDS lanes.
>> +
>> +      Slot          0       1       2       3       4       5       6
>> +                ________________                         _________________
>> +      Clock                     \_______________________/
>> +                  ______  ______  ______  ______  ______  ______  ______
>> +      DATA0     ><__G2__><__R7__><__R6__><__R5__><__R4__><__R3__><__R2__><
>> +      DATA1     ><__B3__><__B2__><__G7__><__G6__><__G5__><__G4__><__G3__><
>> +      DATA2     ><_CTL2_><_CTL1_><_CTL0_><__B7__><__B6__><__B5__><__B4__><
>> +      DATA3     ><_CTL3_><__B1__><__B0__><__G1__><__G0__><__R1__><__R0__><
>> +
>> +      - "vesa-24" - 24-bit data mapping compatible with the [VESA] specification.
>> +        Data are transferred as follows on 4 LVDS lanes.
>> +
>> +      Slot          0       1       2       3       4       5       6
>> +                ________________                         _________________
>> +      Clock                     \_______________________/
>> +                  ______  ______  ______  ______  ______  ______  ______
>> +      DATA0     ><__G0__><__R5__><__R4__><__R3__><__R2__><__R1__><__R0__><
>> +      DATA1     ><__B1__><__B0__><__G5__><__G4__><__G3__><__G2__><__G1__><
>> +      DATA2     ><_CTL2_><_CTL1_><_CTL0_><__B5__><__B4__><__B3__><__B2__><
>> +      DATA3     ><_CTL3_><__B7__><__B6__><__G7__><__G6__><__R7__><__R6__><
>> +
>> +      Control signals are mapped as follows.
>> +
>> +      CTL0: HSync
>> +      CTL1: VSync
>> +      CTL2: Data Enable
>> +      CTL3: 0
> 
> Why do you duplicate what's in display/lvds.yaml?

I don't think any of the other properties from display/lvds.yaml 
currently make any sense to be put into simple-panel, thus I selectively 
picked this one.

If there is a way to selectively pick only the data_mapping, please let 
me know and I send a V2

> 
> This also just made 'data-mapping' valid on non-LVDS panels.

what is the canonical way of restricting the data-mapping property to 
LVDS panels only? Or ist the proper way to go to move the panel I use 
(innolux,g101ice-l01) to its own yaml file, include panel-simple.yaml 
and leave the others alone? I think other LVDS panels might benefit from 
this series though, which is why I think it makes sense to add the 
property to all LVDS panels.

Best regards
Johannes

> 
> Rob
> 

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