linux-kernel - Re: [PATCH] net: ethernet: ti: cpsw_ale: optimize cpsw_ale

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Date:   Fri, 11 Nov 2022 12:25:50 +0200
From:   Roger Quadros <rogerq@...nel.org>
To:     Jakub Kicinski <kuba@...nel.org>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Ido Schimmel <idosch@...sch.org>,
        Nikolay Aleksandrov <razor@...ckwall.org>
Cc:     davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com,
        vigneshr@...com, srk@...com, linux-omap@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: ethernet: ti: cpsw_ale: optimize cpsw_ale_restore()

Hi Jakub,

On 10/11/2022 22:32, Jakub Kicinski wrote:
> On Thu, 10 Nov 2022 11:39:47 +0200 Roger Quadros wrote:
>>> Maybe my tree is old but I see we clear only if there is a netdev that  
>>
>> This patch depends on this series
>> https://lore.kernel.org/netdev/20221104132310.31577-3-rogerq@kernel.org/T/
> 
> I do have those in my tree.
> 
>>> needs to be opened but then always call ale_restore(). Is that okay?  
>>
>> If netdev is closed and opened ale_restore() is not called.
>> ale_restore() is only called during system suspend/resume path
>> since CPSW-ALE might have lost context during suspend and we want to restore
>> all valid ALE entries.
> 
> Ack, what I'm referring to is the contents of am65_cpsw_nuss_resume().
> 
> I'm guessing that ALE_CLEAR is expected to be triggered by
> cpsw_ale_start().
> 
> Assuming above is true and that ALE_CLEAR comes from cpsw_ale_start(),
> the call stack is:
> 
>  cpsw_ale_start()
>  am65_cpsw_nuss_common_open()
>  am65_cpsw_nuss_ndo_slave_open()
>  am65_cpsw_nuss_resume()
> 
> but resume() only calls ndo_slave_open under certain conditions:
> 
>         for (i = 0; i < common->port_num; i++) {                                  
>                 if (netif_running(ndev)) {                                      
>                         rtnl_lock();                                            
>                         ret = am65_cpsw_nuss_ndo_slave_open(ndev);    
> 
> Is there another path? Or perhaps there's nothing to restore 
> if all netdevs are down?

I see your point now. We are missing a ALE_CLEAR if all interfaces were
down during suspend/resume.
In this case the call to cpsw_ale_restore() is pointless as ALE will be
cleared again when one of the interfaces is brought up.

I'll revise the patch to call cpsw_ale_restore only if any interface
was running.

> 
>> I have a question here. How should ageable entries be treated in this case?
> 
> Ah, no idea :) Let's me add experts to To:

Thanks.

cheers,
-roger