netdev - Re: [PATCH RFC net] net: dsa: mv88e6xxx: allow use of PHYs on CPU and DSA ports

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Message-ID: <Ya94roatTK0y7t70@lunn.ch>
Date:   Tue, 7 Dec 2021 16:07:26 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Martyn Welch <martyn.welch@...labora.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH RFC net] net: dsa: mv88e6xxx: allow use of PHYs on CPU
 and DSA ports

On Tue, Dec 07, 2021 at 02:58:26PM +0000, Russell King (Oracle) wrote:
> On Tue, Dec 07, 2021 at 03:54:37PM +0100, Andrew Lunn wrote:
> > On Tue, Dec 07, 2021 at 10:59:19AM +0000, Russell King (Oracle) wrote:
> > > Martyn Welch reports that his CPU port is unable to link where it has
> > > been necessary to use one of the switch ports with an internal PHY for
> > > the CPU port. The reason behind this is the port control register is
> > > left forcing the link down, preventing traffic flow.
> > > 
> > > This occurs because during initialisation, phylink expects the link to
> > > be down, and DSA forces the link down by synthesising a call to the
> > > DSA drivers phylink_mac_link_down() method, but we don't touch the
> > > forced-link state when we later reconfigure the port.
> > > 
> > > Resolve this by also unforcing the link state when we are operating in
> > > PHY mode and the PPU is set to poll the PHY to retrieve link status
> > > information.
> > > 
> > > Reported-by: Martyn Welch <martyn.welch@...labora.com>
> > > Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
> > 
> > Hi Russell
> > 
> > It would be good to have a Fixes: tag here, to help with back porting.
> 
> Oh, I thought this was a new development, not a regression. Do you have
> a pointer to the earlier bits of the thread please, e.g. the message ID
> of the original report.

This all seems to be part of:

b98043f66e8c6f1fd75d11af7b28c55018c58d79.camel@...labora.com

It looks like 5.15-rc3 has issues, but i suspect it goes back further.
I'm also assuming it is a regression, not that it never worked in the
first place. Maybe i'm wrong?

   Andrew