Messages in this thread | | | Date | Mon, 10 Jun 2019 23:11:33 +0200 | From | Andrew Lunn <> | Subject | Re: [PATCH net-next] net: dsa: Deal with non-existing PHY/fixed-link |
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> Hi Florian, > > Can you give an example of when this is a valid use case, and why > fixed-link is not appropriate?
A DSA link is used to connect two switches together. ZII devel b and c are two boards which does this. Such links have the MACs connected back to back, no PHYs involved. You can also connect a SoC interface to the CPU port of a switch without having PHYs involved.
We have defined that CPU and DSA ports are always configured by the driver to there maximum speed. Because of this, you often don't need a fixed-link on CPU or DSA ports. So you will see most DT blobs don't have any sort of PHY for the CPU or DSA ports.
You only need fixed-link when you need to slow a port down, e.g. a SoC FE port connected to a switch 1G port.
Andrew
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