[PATCH 1/2] dt-bindings: drm/bridge: ti-sn65dsi83: Add TI SN65DSI83 bindings

[Doug Anderson]

Hi,

On Thu, Feb 4, 2021 at 10:09 AM Marek Vasut <marex at denx.de> wrote:
>
> On 2/4/21 6:15 PM, Doug Anderson wrote:
>
> Hi,
>
> [...]
>
> >> +properties:
> >> +  compatible:
> >> +    const: ti,sn65dsi83
> >> +
> >> +  reg:
> >> +    const: 0x2d
> >> +
> >> +  enable-gpios:
> >> +    maxItems: 1
> >> +    description: GPIO specifier for bridge_en pin (active high).
> >
> > I see two regulators: vcc and vcore.  Shouldn't those be listed?
>
> Those are not implemented and not tested, so if someone needs them later
> on, they can be added then.

Sure.  I guess it can go either way.  For the regulator it'd the kind
of thing that's super easy to add support for and hard to mess up.


> >> +          endpoint:
> >> +            type: object
> >> +            additionalProperties: false
> >> +            properties:
> >> +              remote-endpoint: true
> >> +              data-lanes:
> >> +                description: array of physical DSI data lane indexes.
> >
> > The chip doesn't allow for arbitrary remapping here, right?  So you're
> > just using this as the official way to specify the number of lanes?  I
> > guess the only valid values are:
> >
> > <0>
> > <0 1>
> > <0 1 2>
> > <0 1 2 3>
>
> Shouldn't that be <1 2 3 4> ?

The data manual refers to the channels starting at 0, so if it's
arbitrary that seems a better way to go?


> > In sn65dsi86 we attempted to enforce that a valid option was selected
> > for the output lanes.  Could you do something similar?  If nothing
> > else adding a description of the valid options would be good.
>
> I saw the binding, but I was under the impressions the DSI86 can do lane
> reordering, isn't that the case ? Maybe I misunderstood it.

DSI86 can reorder the output lanes quite flexibly.  It can't reorder
the input lanes, though.


> But yes, if you have a suggestion how to make a non-cryptic list of
> those four lane mapping options, please do share this info.

I doubt I can write this correctly without a whole lot of futzing /
messing, but maybe something like:

data-lanes:
  oneOf:
    - items:
        - 0
    - items:
        - 0
        - 1
    - items:
        - 0
        - 1
        - 2
    - items:
        - 0
        - 1
        - 2
        - 3