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In general, for MIPI DSI there are three ways to represent the
pipeline for an upstream bridge to find the connected downstream
panel or bridge.
1. Child panel or bridge as a conventional device tree child node.
2. Child panel or bridge as an OF-graph port node.
3. Child panel or bridge as an OF-graph ports node.
There are three different downstream panels or bridges that are
possible to connect an upstream DSI host bridge - DSI Panel,
DSI Bridge, and I2C-Configured DSI bridge.
An example of the downstream panel represented as a child node,
&dsi {
compatible = "samsung,exynos5433-mipi-dsi";
ports {
port@0 {
reg = <0>;
dsi_to_mic: endpoint {
remote-endpoint = <&mic_to_dsi>;
};
};
};
panel@0 {
reg = <0>;
};
};
An example of the downstream bridge represented as a port node,
&i2c4 {
bridge@2c {
compatible = "ti,sn65dsi84";
ports {
port@0 {
reg = <0>;
bridge_in_dsi: endpoint {
remote-endpoint = <&dsi_out_bridge>;
data-lanes = <1 2>;
};
};
port@2 {
reg = <2>;
bridge_out_panel: endpoint {
remote-endpoint = <&panel_out_bridge>;
};
};
};
};
};
&dsi {
compatible = "fsl,imx8mm-mipi-dsim";
port {
dsi_in_lcdif: endpoint@0 {
reg = <0>;
remote-endpoint = <&lcdif_out_dsi>;
};
dsi_out_bridge: endpoint@1 {
reg = <1>;
remote-endpoint = <&bridge_in_dsi>;
};
};
};
An example of the downstream bridge represented as a ports node,
&dsi {
compatible = "fsl,imx8mm-mipi-dsim";
ports {
port@0 {
reg = <0>;
dsi_in_lcdif: endpoint@0 {
reg = <0>;
remote-endpoint = <&lcdif_out_dsi>;
};
};
port@1 {
reg = <1>;
dsi_out_bridge: endpoint {
remote-endpoint = <&bridge_in_dsi>;
};
};
};
In, summary it is possible to represent all three downstream slaves
devices using OF-graph port or ports node however only DSI Panel and
DSI Bridge are possible but not possible to represent I2C-Configured
DSI bridge child nodes since I2C-Configure bridges are child of I2C
node, not upstream DSI host bridge and it is must represent them
endpoint port linking.
This indeed means, the OF-graph port or ports representation is
mandatory for I2C-Configured DSI bridges.
This patch tries to add an OF-graph port or ports representation
detection code on top of existing child node detection.
It is possible to replace the entire detection code using existing
drm_of helper drm_of_find_panel_or_bridge but it will break the
Exynos DSI since the pipeline doesn't support OF-graph port or ports
node.
Overall, this patch has a combination of child and OF-graph pipeline
detections in order to support the backward compatibility of Exynos
DSI child node and i.MX8M Mini/Nano/Plus OF-graph port or ports
node pipelines.
This is the first common DSI host bridge driver that needs to support
all possible downstream connection pipeline combinations.
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>