On Sunday, March 8th, 2026 at 17:13, Krzysztof Kozlowski <[email protected]>
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.
Regards,
Cristian.
