On Tue, 6 Jun 2017 15:40:25 +0300
Tomi Valkeinen <tomi.valkei...@ti.com> wrote:
> On 06/06/17 12:35, Boris Brezillon wrote:
> > On Sat, 3 Jun 2017 23:43:17 +0530
> > Archit Taneja <arch...@codeaurora.org> wrote:
> >
> >> Hi,
> >>
> >> On 06/02/2017 05:34 PM, Boris Brezillon wrote:
> >>> Document the bindings used for the Cadence DSI bridge.
> >>>
> >>> Signed-off-by: Boris Brezillon <boris.brezil...@free-electrons.com>
> >>> ---
> >>> .../bindings/display/bridge/cdns,dsi.txt | 55
> >>> ++++++++++++++++++++++
> >>> 1 file changed, 55 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..770c5c5b1e93
> >>> --- /dev/null
> >>> +++ b/Documentation/devicetree/bindings/display/bridge/cdns,dsi.txt
> >>> @@ -0,0 +1,55 @@
> >>> +Cadence DSI bridge
> >>> +==================
> >>> +
> >>> +The Cadence DSI bridge is a DPI to DSI bridge supporting up to 4 DSI
> >>> lanes.
> >>
> >> Is this a separate chip, or an IP integrated into SoCs?
> >
> > It's supposed to be integrated into SoCs.
> >
> >> If it's the
> >> latter, I don't think DPI on the its input side is the right term to
> >> use. Maybe RGB would be more appropriate here.
> >
> > Well, the datasheet explicitly mentions DPI, and you can also send
> > pixels in YUV422 and YUV420 format on this bus, so I don't think RGB is
> > appropriate, but if you really want me to use RGB I can change that.
> >
> > BTW, can you detail why DPI is not appropriate for internal parallel
> > busses. I don't understand why it makes a difference when the bus is exposed
> > through external pins.
>
> I think MIPI DPI is fine, if it is indeed MIPI DPI. But mot all parallel
> video busses are MIPI DPI.
>
> >>> +Required subnodes:
> >>> +- ports: Ports as described in
> >>> Documentation/devicetree/bindings/graph.txt.
> >>> + Currently contains a single input port at address 0 representing the
> >>> DPI
> >>> + input. Other ports will be added later to support the SDI inputs.
> >>> + Port 0 should be connected to a DPI encoder output.
> >>
> >> The output of the DSI bridge may be another bridge, which could be i2c
> >> controlled. In that case, it won't be a child of the DSI bridge. For
> >> such scenarios, we might want to define an output port for the bridge.
> >
> > Hm, okay. IIRC, this is something you mentioned when I asked how to
> > describe input/output ports for a DSI bridge a while ago.
> >
> > I'm still not sure how the links between input and output endpoint are
> > supposed to be described.
> >
> > For example, if you take the case where you have the DSI device
> > directly described under the DSI host controller, should I create
> > another node for this output port? Something like the following?
> >
> > dsi@xxx {
> > #address-cells = <1>;
> > #size-cells = <0>;
> >
> > ports {
> > #address-cells = <1>;
> > #size-cells = <0>;
> > dpi_in: port@0 {
> > reg = <0>;
> > #address-cells = <1>;
> > #size-cells = <0>;
> >
> > endpoint@0 {
> > remote-endpoint = <&dpi_out>;
> > };
> > };
> >
> > dsi_out0: port@1 {
> > reg = <1>;
> > #address-cells = <1>;
> > #size-cells = <0>;
> >
> > dsi_out0: endpoint@0 {
> > remote-endpoint = <&dsi_panel0_in>;
> > };
> > };
> >
> > dsi_out0: port@2 {
> > reg = <2>;
> > #address-cells = <1>;
> > #size-cells = <0>;
> >
> > dsi_out1: endpoint@0 {
> > remote-endpoint = <&dsi_panel1_in>;
> > };
> > };
> > };
> >
> > panel@0 {
> > compatible = "...";
> > reg = <0>;
> > #address-cells = <1>;
> > #size-cells = <0>;
> >
> > port@0 {
> > #address-cells = <1>;
> > #size-cells = <0>;
> > reg = <0>;
> >
> > dsi_panel0_in: endpoint@0 {
> > remote-endpoint = <&dsi_out0>;
> > };
> > };
> > };
> >
> > panel@1 {
> > compatible = "...";
> > reg = <1>;
> > #address-cells = <1>;
> > #size-cells = <0>;
> >
> > port@0 {
> > #address-cells = <1>;
> > #size-cells = <0>;
> > reg = <0>;
> >
> > dsi_panel1_in: endpoint@0 {
> > remote-endpoint = <&dsi_out1>;
> > };
> > };
> > };
> > };
> >
>
> The ports & endpoints describe the video path, and the node child-parent
> relationship describe the control path. And "port" is a physical
> connector of some sort, and endpoint is a virtual channel or such.
>
> So, you can have DSI peripherals which are either children of the DSI
> bridge, and can be controlled with DSI commands. Or, you can have, say,
> i2c peripherals, defined under an i2c node, which just take the video
> stream from the DSI bridge. Both would have similar ports & endpoints,
> but the DT nodes would be located under different parents.
>
> Also, you can't have two output ports unless the DSI bridge has actually
> multiple output pins. If the two panels are connected to the same DSI
> pins, and the DSI virtual channel is used to direct the output to the
> correct panel, then these should be endpoints.
Okay. Thanks for the clarification. Can you confirm that this version
is correct?
dsi@xxx {
#address-cells = <1>;
#size-cells = <0>;
ports {
#address-cells = <1>;
#size-cells = <0>;
dpi_in: port@0 {
reg = <0>;
#address-cells = <1>;
#size-cells = <0>;
endpoint@0 {
remote-endpoint = <&dpi_out>;
};
};
dsi_out: port@1 {
reg = <1>;
#address-cells = <1>;
#size-cells = <0>;
dsi_out_vc0: endpoint@0 {
reg = <0>;
remote-endpoint = <&dsi_panel0_in>;
};
dsi_out_vc1: endpoint@1 {
reg = <1>;
remote-endpoint = <&dsi_panel1_in>;
};
};
};
panel@0 {
compatible = "...";
reg = <0>;
#address-cells = <1>;
#size-cells = <0>;
port@0 {
#address-cells = <1>;
#size-cells = <0>;
reg = <0>;
dsi_panel0_in: endpoint@0 {
reg = <0>;
remote-endpoint = <&dsi_out_vc0>;
};
};
};
panel@1 {
compatible = "...";
reg = <1>;
#address-cells = <1>;
#size-cells = <0>;
port@0 {
#address-cells = <1>;
#size-cells = <0>;
reg = <0>;
dsi_panel1_in: endpoint@0 {
reg = <0>;
remote-endpoint = <&dsi_out_vc1>;
};
};
};
};
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