netdev - Re: [PATCH net] net: mscc: ocelot: don't let phylink re-enable TX PAUSE on the NPI port

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Date:   Wed, 12 Jan 2022 20:37:31 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Florian Fainelli <f.fainelli@...il.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        "UNGLinuxDriver@...rochip.com" <UNGLinuxDriver@...rochip.com>,
        Xiaoliang Yang <xiaoliang.yang_1@....com>
Subject: Re: [PATCH net] net: mscc: ocelot: don't let phylink re-enable TX
 PAUSE on the NPI port

On Wed, Jan 12, 2022 at 12:31:14PM -0800, Florian Fainelli wrote:
> Still quite a lot of retries, do you know where they are coming from?

Yes, they are coming from the fact that the CPU port runs at 2.5G and
the front port at 1G, and as mentioned, there isn't any flow control
when the CPU port is used in NPI mode.

Flow control on that port pair _is_ available when the CPU port is used
with the ocelot-8021q tagging protocol, which is the reason why I
updated the device tree to declare "pause" for those fixed-links.
We can't enable or disable flow control on a fixed-link at runtime in
Linux.