From: Andrew Lunn <andrew@lunn.ch>
To: Vladimir Oltean <olteanv@gmail.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>,
netdev <netdev@vger.kernel.org>,
Ioana Ciornei <ioana.ciornei@nxp.com>,
Russell King <rmk+kernel@armlinux.org.uk>,
Vivien Didelot <vivien.didelot@gmail.com>,
"David S. Miller" <davem@davemloft.net>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net-next] net: dsa: Deal with non-existing PHY/fixed-link
Date: Mon, 10 Jun 2019 23:11:33 +0200 [thread overview]
Message-ID: <20190610211133.GC2191@lunn.ch> (raw)
In-Reply-To: <CA+h21hrcymxF7zk4yHFGhjxbLERTCU6WkfzLGQVoZ5Yxoo4xxw@mail.gmail.com>
> 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
next prev parent reply other threads:[~2019-06-10 21:11 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-10 19:31 [PATCH net-next] net: dsa: Deal with non-existing PHY/fixed-link Florian Fainelli
2019-06-10 19:53 ` Vladimir Oltean
2019-06-10 20:49 ` Ioana Ciornei
2019-06-10 21:11 ` Andrew Lunn [this message]
2019-06-10 21:15 ` Andrew Lunn
2019-06-12 18:01 ` David Miller
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