Hello, I am trying to develop a bridge driver for a Serializer (DSI Peripheral) that has two DSI Ports with the primary control bus being I2C. The host is MediaTek MT2172 SoC (Compatible with MT8173). I defined the device tree referring to example 5 in mipi-dsi-bus[1].
However the configuration does not work. The issue I am facing is that drm_bridge_attach returns EBUSY for the second DSI (dsi1). This is because the bridge is already attached to another device (dsi0). This seems to be inline with the concept of crtc --> encoder --> bridge -> connector. i.e. there is 1-1 relationship. But seems contradictory to the device tree layout.
I looked up all the existing examples but none seemed to match my use case. I considered the following options
1) Modify drm_bridge to keep up to n (<= 4) downstream devices. The idea is to have something like the following ( please excuse the representation)
crtc1 --> encoder1 -->\ / - - >connector1 \ -> bridge - >/ / \ crtc2 --> encoder2 -->/ \ - - >connector2
The issue with this approach is, it is plainly incorrect based on my understanding
2) Define a second bridge in the device tree with may be a dummy <reg> and connect the endpoint of dsi1_out to an endpoint within this bridge. This seems counter-intuitive as actually there is just one bridge device.
I am personally leaning towards approach 1. Any suggestions? Any examples that you can point me to?
Thanks, Sriram
[1] https://www.kernel.org/doc/Documentation/devicetree/bindings/display/mipi-ds...