Qualcomm Soundwire controller drivers do not support multi-link setups, so DAI .set_stream() callback will not be used. What's more, if called it will overwrite the sdw_stream_runtime runtime set in DAI .startup (qcom_swrm_startup()) causing issues (unsupported multi-link error) when two Soundwire controllers are passed as codec DAIs.
This last sentence is confusing at best.
A controller can have one or more managers, each of whom can have one or more peripherals.
only peripherals should expose codec DAIs, managers should expose CPU DAIs.
Put differently, the controller is the host part while the peripheral is the codec part. "controllers passed as codec DAIs" is not really possible, or this was a typo?
No, it wasn't a typo. Take a look here: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch...
The <&swr0 0> is the controller, although probably I should call it manager, but in case of Qualcomm I think they are 1-to-1.
Is this a case where the SoundWire manager is part of a codec?
In that case, how are the SoundWire peripheral modeled?
The .set_stream callback was really meant to be used when you have a CPU DAI for the manager and a codec DAI for the peripheral(s). This seems to be a different configuration where CPU and codec DAIs are mixed.