Re: [PATCH 1/6] dt-bindings: display: panel: Add Novatek NT35532 LCD DSI

[Krzysztof Kozlowski <krzk@kernel.org>]

On 09/03/2026 15:52, cristian_ci wrote:
> On Sunday, March 8th, 2026 at 17:13, Krzysztof Kozlowski <krzk@kernel.org> wrote:
> 
>>> +  vsp-supply:
>>> +    description: positive voltage supply for analog circuits
>>
>> Both are odd. Datasheet says vci, vddi, vddam and optional avdd, avee.
>>
>> There is no VSN and VSP. Otherwise please point the page in datasheet or
>> some schematics.
>>
>> Best regards,
>> Krzysztof
>>
> 
> I'm not sure about that. Writing panel dt-bindings has been based pretty mostly on vendor devicetree - which also describes somehow the panel and makes that working with the final product released to the market - so I've to necessarily consider that.
> Then, I could agree that vendor devicetree might be not compliant with upstream rules and could possibly make mistakes with describing the hardware, so I'd like to find a way to describe that in a more proper way, according to upstream rules.
> 
> That said, vendor devicetree describes lists four power supplies for  DSI: 'vdd', 'vddio', 'lab' and 'ibb' (which have the following property names, respectively, in qcom,mdss_dsi_ctrl node: 'vdd-supply', 'vddio-supply', 'lab-supply' and 'ibb-supply'.
> Two of these are related to ds/controller (apparently, 'vddio' should match VDDI power supply in NT35532 datasheet.
> 
> The remaining two supplies are related to panel ('lab' and 'ibb'). These ones are two 'external ' regulators ('external' from NT35532 perspective), which provide power supply to display, located in the qcom PMIC (in this case, that should be PMI8950). WRT to power supply names described in the bindings ('vsp-supply' and 'vsn-supply') are the same as 'lab-supply' and 'ibb-supply', just named differently in the vendor devicetrees.
> 
> Usage of 'vsp'/'vsn' naming for power supply properties is grounded on they commonly being used at upstream (different panel bindings make use of these properties), on one side, and also described on schematics of devices with the same hardware configuration (LCD_VSN and LCD_VSP), on the other.
> 
> In the meantime, I've found out schematics for 'xiaomi-mido' (another MSM8953 device) - a variant of this device is shipped with a panel also using NT35532 IC (just like my device) - and LCD_VSN/LCD_VSP are clearly shown there too.
> 
> I couldn't find much more information about the display on my device and the only resources available about that are those listed above, as of today. In light of my reply, I ask if it is still necessary to describe, in the bindings, power supply properties properties not used currently in the board DTS file.

Please wrap your answers so this will be possible to parse.

You write bindings matching the hardware and for the hardware, not for
the downstream code. You cannot add supplies which do not exist
regardless what some vendor wrote somewhere and yes, you must describe
all known supplies for this device, especially that datasheet is
available publicly.

Best regards,
Krzysztof