netdev - 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 13:47:34 +0530
From: MD Danish Anwar <danishanwar@...com>
To: Roger Quadros <rogerq@...nel.org>, 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 08/09/23 13:16, Roger Quadros wrote:
> 
> 
> 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.
> 

I did some further testing on switch mode. The basic functionality would
work without a bridge as well. This will need one modification in driver
but even without bridge switching will work.

When enabling switch mode the driver sets the HOST_MAC_ADDR to the
bridge's addr. If bridge is not there, this will result in KERNEL NULL
POINTER crash.

icssg_class_set_host_mac_addr(prueth->miig_rt,
prueth->hw_bridge_dev->dev_addr);

However if we change this to only set when bridge is there, it works

if (prueth->hw_bridge_dev)
	icssg_class_set_host_mac_addr(prueth->miig_rt,
prueth->hw_bridge_dev->dev_addr);

With this change forwarding works in switch mode without setting up the
bridge. Just loading the switch firmware is enough.


> 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?>

To summarize, yes it can work at this point.

>>  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
> 

-- 
Thanks and Regards,
Danish