linux-kernel - RE: [EXT] Re: [V2 net-next] net: mvpp2: Add reserved port private flag configuration

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Date:   Mon, 22 Mar 2021 18:24:05 +0000
From:   Stefan Chulski <stefanc@...vell.com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     "kuba@...nel.org" <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "thomas.petazzoni@...tlin.com" <thomas.petazzoni@...tlin.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Nadav Haklai <nadavh@...vell.com>,
        Yan Markman <ymarkman@...vell.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "mw@...ihalf.com" <mw@...ihalf.com>,
        "rmk+kernel@...linux.org.uk" <rmk+kernel@...linux.org.uk>,
        "atenart@...nel.org" <atenart@...nel.org>,
        "rabeeh@...id-run.com" <rabeeh@...id-run.com>
Subject: RE: [EXT] Re: [V2 net-next] net: mvpp2: Add reserved port private
 flag configuration

> > CM3 won't use this interface till ethtool priv flag was set, it can be done by
> communication over CM3 SRAM memory.
> >
> > > How does CM3 know the status of the link?
> >
> > CM3 has access to MAC registers and can read port status bit.
> >
> > > How does CM3 set its
> > > flow control depending on what auto-neg determines, etc?
> >
> > Same as PPv2 Packet Processor RX and TX flow don't really care about auto-
> neg, flow control, etc.
> > CM3 can ignore it, all this stuff handled in MAC layer. CM3 just polling RX
> descriptor ring and using TX ring for transmit.
> >
> > >
> > > > 3. In some cases we need to dynamically switch the port "user"
> > > > between CM3 and kernel. So I would like to preserve this
> > > > functionality.
> > >
> > > And how do you synchronize between Linux and CM3 so you know how
> is
> > > using it and who cannot use it?
> > >
> > >       Andrew
> >
> > I can add CM3 SRAM update into ethtool priv flag callback, so CM3 won't
> use port till it was reserved to CM3.
> 
> I really think you need to step back here and look at the bigger picture. If
> linux should not use the interface, it should not exist. If it does not exist, you
> cannot use ethtool on it.
> 
> What you might want to consider is adding remoteproc support between
> Linux on the main processor and whatever you have on the CM3. You can
> use RPMsg to send requests back and forth between Linux and the CM3. It
> can request that the shared parts of the packet processor are set up for it.
> Linux can tell it when the link comes up? It can request how the PHY auto-
> neg should be configured.
> 
> 	Andrew

I would check this option. 

Thanks,
Stefan.