Cristian
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On Monday, March 9th, 2026 at 16:08, Krzysztof Kozlowski <[email protected]>
wrote:
> On 09/03/2026 15:52, cristian_ci wrote:
> > 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.
>
> 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
Vendor has also described the hardware by storing information (by including
info
about panel too) directly inside the device itself (/sys/firmware/fdt).
Though vendor devicetree could possibly contain mistakes, I guess I've to trust
vendor
devicetree (also for the reasons explained in my last reply).
> and yes, you must describe
> all known supplies for this device, especially that datasheet is
> available publicly.
Based on what you said, the following questions have raised:
- have properties (mentioned by you) be defined
(apart 'vddi', which most likely is actually 'vddio-supply',
already defined within mdss_dsi0 node) outside of 'panel' node?
(and related to dsi/controller rather than panel, instead)
- have those properties (mentioned by you) set as 'optional'
in the bindings, rather than set as 'required'?
(since panel works without most of them defined in the
board DTS file)
> Best regards,
> Krzysztof
>
