Re: [PATCH v3 2/2] dt-bindings: drm/bridge: Document Cadence DSI bridge bindings

[Boris Brezillon <boris.brezillon-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>]

Hi Andrzej,

On Fri, 01 Sep 2017 08:28:13 +0200
Andrzej Hajda <a.hajda-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org> wrote:

> On 31.08.2017 17:55, Boris Brezillon wrote:
> > Document the bindings used for the Cadence DSI bridge.
> >
> > Signed-off-by: Boris Brezillon <boris.brezillon-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
> > ---
> > Changes in v3:
> > - Fix clock names in the example
> > - Document how to represent DSI devices that are controller through
> >   an external bus like I2C or SPI
> >
> > Changes in v2:
> > - None
> > ---
> >  .../bindings/display/bridge/cdns,dsi.txt           | 109 +++++++++++++++++++++
> >  1 file changed, 109 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/display/bridge/cdns,dsi.txt
> >
> > diff --git a/Documentation/devicetree/bindings/display/bridge/cdns,dsi.txt b/Documentation/devicetree/bindings/display/bridge/cdns,dsi.txt
> > new file mode 100644
> > index 000000000000..c70008bd8c0d
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/display/bridge/cdns,dsi.txt
> > @@ -0,0 +1,109 @@
> > +Cadence DSI bridge
> > +==================
> > +
> > +The Cadence DSI bridge is a DPI to DSI bridge supporting up to 4 DSI lanes.
> > +
> > +Required properties:
> > +- compatible: should be set to "cdns,dsi-1.3.1".
> > +- reg: physical base address and length of the controller's registers.
> > +- interrupts: interrupt line connected to the DSI bridge.
> > +- clocks: DSI bridge clocks.
> > +- clock-names: must contain "pclk" and "sysclk".
> > +- phys: phandle link to the MIPI D-PHY controller.
> > +- phy-names: must contain "dphy".
> > +- #address-cells: must be set to 1.
> > +- #size-cells: must be set to 0.
> > +
> > +Required subnodes:
> > +- ports: Ports as described in Documentation/devicetree/bindings/graph.txt.
> > +  2 ports are available:
> > +  * port 0: this port is only needed if some of your DSI devices are
> > +	    controlled through  an external bus like I2C or SPI. Can have at
> > +	    most 4 endpoints. The endpoint number is directly encoding the
> > +	    DSI virtual channel used by this device.
> > +  * port 1: represents the DPI input.
> > +  Other ports will be added later to support the new kind of inputs.  
> 
> I think usual practice is to use lower numbers for input ports, higher
> for output ports.
> Is there a reason to do it this way?

The main reason I did that is because we only have one output port and
can have 1, 2 or 3 input ports: one is the DPI and the 2 others are
called SDI (some kind of serial input). I thought it would be better to
have all inputs using contiguous port numbers, and if we put inputs
first that means having a hole between the input and output port (port 0
would be the DPI input and port 3 the DSI output).

Honestly, that's just a detail, so if you prefer to have the input
ports start at 0 I'm fine with that.

Regards,

Boris


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