linux-kernel - Re: [PATCH net-next v3 3/3] net: ti: icssg-prueth: Add support for ICSSG switch firmware

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Message-ID: <27d960ed-8e67-431b-a910-e6b2fc12e292@lunn.ch>
Date: Wed, 27 Mar 2024 13:35:54 +0100
From: Andrew Lunn <andrew@...n.ch>
To: MD Danish Anwar <danishanwar@...com>
Cc: Diogo Ivo <diogo.ivo@...mens.com>, Rob Herring <robh@...nel.org>,
	Dan Carpenter <dan.carpenter@...aro.org>,
	Jan Kiszka <jan.kiszka@...mens.com>,
	Simon Horman <horms@...nel.org>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Arnd Bergmann <arnd@...db.de>,
	Vignesh Raghavendra <vigneshr@...com>,
	Vladimir Oltean <vladimir.oltean@....com>,
	Roger Quadros <rogerq@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	"David S. Miller" <davem@...emloft.net>,
	linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, srk@...com, r-gunasekaran@...com
Subject: Re: [PATCH net-next v3 3/3] net: ti: icssg-prueth: Add support for
 ICSSG switch firmware

On Wed, Mar 27, 2024 at 05:10:54PM +0530, MD Danish Anwar wrote:
> Add support for ICSSG switch firmware using existing Dual EMAC driver
> with switchdev.
> 
> Limitations:
> VLAN offloading is limited to 0-256 IDs.
> MDB/FDB static entries are limited to 511 entries and different FDBs can
> hash to same bucket and thus may not completely offloaded
> 
> Switch mode requires loading of new firmware into ICSSG cores. This
> means interfaces have to taken down and then reconfigured to switch
> mode.

Patch 0/3 does not say this. It just shows the interfaces being added
to the bridge. There should not be any need to down the interfaces.

> Example assuming ETH1 and ETH2 as ICSSG2 interfaces:
> 
> Switch to ICSSG Switch mode:
>  ip link set dev eth1 down
>  ip link set dev eth2 down
>  ip link add name br0 type bridge
>  ip link set dev eth1 master br0
>  ip link set dev eth2 master br0
>  ip link set dev br0 up
>  ip link set dev eth1 up
>  ip link set dev eth2 up
>  bridge vlan add dev br0 vid 1 pvid untagged self
> 
> Going back to Dual EMAC mode:
> 
>  ip link set dev br0 down
>  ip link set dev eth1 nomaster
>  ip link set dev eth2 nomaster
>  ip link set dev eth1 down
>  ip link set dev eth2 down
>  ip link del name br0 type bridge
>  ip link set dev eth1 up
>  ip link set dev eth2 up
> 
> By default, Dual EMAC firmware is loaded, and can be changed to switch
> mode by above steps

I keep asking this, so it would be good to explain it in the commit
message. What configuration is preserved over a firmware reload, and
what is lost?

Can i add VLAN in duel MAC mode and then swap into the switch firmware
and all the VLANs are preserved? Can i add fdb entries to a port in
dual MAC mode, and then swap into the swtich firmware and the FDB
table is preserved? What about STP port state? What about ... ?


> +bool prueth_dev_check(const struct net_device *ndev)
> +{
> +	if (ndev->netdev_ops == &emac_netdev_ops && netif_running(ndev)) {
> +		struct prueth_emac *emac = netdev_priv(ndev);
> +
> +		return emac->prueth->is_switch_mode;
> +	}
> +
> +	return false;
> +}

This does not appear to be used anywhere?

     Andrew