drm/sun4i: tcon: get TCON ID and matching engine with remote endpoint ID
The device tree binding for sun4i-drm says: For all connections between components up to the TCONs in the display pipeline, when there are multiple components of the same type at the same depth, the local endpoint ID must be the same as the remote component's index. For example, if the remote endpoint is Frontend 1, then the local endpoint ID must be 1. We should be able to get the TCON's ID directly from any of the remote endpoints from its input port. With the ID, we can then go through the list of registered engines and find a matching one by ID. However the A31 device tree is incorrect. We assumed that there were no cross pipeline connections between the backends and TCONs. As a result, in all the endpoints between the backends and TCONs of the second display pipeline, the endpoint IDs were incorrectly set to 0, when in fact they should've been set to 1. To maintain compatibility with this incorrect device tree, we first check if the TCON's input port has 1 or many endpoints. If there are more than 1, then it is likely a fixed version, and we can proceed with the new method. If there is only 1 endpoint, then it is possibly an incorrect version, or it could be the SoC only has one pipeline. In either case we fall back to using the old method of traversing the input connections to find a matching engine, and then get its ID. Signed-off-by:Chen-Yu Tsai <wens@csie.org> Signed-off-by:
Maxime Ripard <maxime.ripard@free-electrons.com> Link: https://patchwork.freedesktop.org/patch/msgid/20170908075016.18657-5-wens@csie.org
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