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From:   Stefan Chulski <stefanc@marvell.com>
To:     Russell King - ARM Linux admin <linux@armlinux.org.uk>
CC:     "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "thomas.petazzoni@bootlin.com" <thomas.petazzoni@bootlin.com>,
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        Nadav Haklai <nadavh@marvell.com>,
        Yan Markman <ymarkman@marvell.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "kuba@kernel.org" <kuba@kernel.org>,
        "mw@semihalf.com" <mw@semihalf.com>,
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        "atenart@kernel.org" <atenart@kernel.org>,
        "rabeeh@solid-run.com" <rabeeh@solid-run.com>
Subject: RE: [EXT] Re: [net-next] net: mvpp2: Add reserved port private flag
 configuration
Thread-Topic: [EXT] Re: [net-next] net: mvpp2: Add reserved port private flag
 configuration
Thread-Index: AQHXFZGs7YE0C+mbQkm8VJDJz1s2Cap9lBUAgADY6YA=
Date:   Thu, 11 Mar 2021 08:12:53 +0000
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 <20210310190018.GH1463@shell.armlinux.org.uk>
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> > From: Stefan Chulski <stefanc@marvell.com>
> >
> > According to Armada SoC architecture and design, all the PPv2 ports
> > which are populated on the same communication processor silicon die
> > (CP11x) share the same Classifier and Parser engines.
> >
> > Armada is an embedded platform and therefore there is a need to
> > reserve some of the PPv2 ports for different use cases.
> >
> > For example, a port can be reserved for a CM3 CPU running FreeRTOS for
> > management purposes or by user-space data plane application.
> >
> > During port reservation all common configurations are preserved and
> > only RXQ, TXQ, and interrupt vectors are disabled.
>=20
> If a port is reserved for use by the CM3, what are the implications for L=
inux
> running on the AP? Should Linux have knowledge of the port?
> What configurations of the port should be permitted?

In reserved mode all port TXQ's closed(Linux won't transmit any packet from=
 this ports) and
RX interrupts disabled(Linux won't receive any packet). We still can change=
 port MAC address, do port UP/DOWN from Linux running on the AP.
Only permitted configurations Is MTU change.
Driver .ndo_change_mtu callback has logic that switch between percpu_pools =
and shared pools buffer mode, we should avoid this since buffer management =
not done by Kernel.

> I think describing how a port reserved for use by the CM3 CPU should appe=
ar
> to Linux is particularly important for the commit commentry to cover.

Ok, I would add more info to commit message.

Thanks,
Stefan.