linux-kernel - Re: [RFC PATCH net-next 3/4] net: ti: icssg-prueth: Add support for ICSSG switch firmware on AM654 PG2.0 EVM

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Date:   Fri, 8 Sep 2023 10:46:35 +0300
From:   Roger Quadros <rogerq@...nel.org>
To:     MD Danish Anwar <danishanwar@...com>, Andrew Lunn <andrew@...n.ch>
Cc:     Simon Horman <horms@...nel.org>,
        Vignesh Raghavendra <vigneshr@...com>,
        Jacob Keller <jacob.e.keller@...el.com>,
        Richard Cochran <richardcochran@...il.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org, srk@...com,
        r-gunasekaran@...com, Pekka Varis <p-varis@...com>
Subject: Re: [RFC PATCH net-next 3/4] net: ti: icssg-prueth: Add support for
 ICSSG switch firmware on AM654 PG2.0 EVM



On 05/09/2023 11:43, MD Danish Anwar wrote:
> On 04/09/23 19:38, Andrew Lunn wrote:
>>> Switch mode requires loading of new firmware into ICSSG cores. This
>>> means interfaces have to taken down and then reconfigured to switch mode
>>> using devlink.
>>
>> Can you always run it in switch mode, just not have the ports in a
>> bridge?
>>
>> 	Andrew
> 
> No, we can't always run it in switch mode. Switch mode requires loading
> of different firmware. The switch firmware only supports switch
> operations. If the ports are not in a bridge in switch mode, the normal
> functionalities will not work. We will not be able to send / receive /
> forward packets in switch mode without bridge.
> 
> When device is booted up, the dual EMAC firmware is loaded and ICSSG
> works in dual EMAC mode with both ports doing independent TX / RX.
> 
> When switch mode is enabled, dual EMAC firmware is unloaded and switch
> firmware is loaded. The ports become part of the bridge and the two port
> together acts as a switch.
> 

Since we are loading the switch firmware and the switch logic is in firmware,
it means we don't really need Linux help to do basic switching on the external
ports.

I suppose Andrews question was, can it work as a switch after switching
from dual-emac to switch mode and not setting up the Linux bridge.

e.g. Looking at your command list

> Switch to ICSSG Switch mode:
>  ip link set dev eth1 down
>  ip link set dev eth2 down
>  devlink dev param set platform/icssg2-eth name \
>  switch_mode value 1 cmode runtime

At this point, can it work as a switch. If not, why?

>  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

-- 
cheers,
-roger