netdev - Re: [PATCH v8 net-next 0/2] mv88e6xxx: Add MAB offload support

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Date:   Fri, 18 Nov 2022 14:37:26 +0100
From:   netdev@...io-technology.com
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Ido Schimmel <idosch@...sch.org>, davem@...emloft.net,
        kuba@...nel.org, netdev@...r.kernel.org,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 net-next 0/2] mv88e6xxx: Add MAB offload support

On 2022-11-16 11:24, Vladimir Oltean wrote:
> On Tue, Nov 15, 2022 at 07:40:02PM +0100, netdev@...io-technology.com 
> wrote:
>> So, I will not present you with a graph as it is a tedious process 
>> (probably
>> it is some descending gaussian curve wrt timeout occurring).
>> 
>> But 100ms fails, 125 I had 1 port fail, at 140, 150  and 180 I saw 
>> timeouts
>> resulting in fdb add fails, like (and occasional port fail):
>> 
>> mv88e6085 1002b000.ethernet-1:04: Timeout while waiting for switch
>> mv88e6085 1002b000.ethernet-1:04: port 0 failed to add 
>> be:7c:96:06:9f:09 vid
>> 1 to fdb: -110
>> 
>> At around 200 ms it looks like it is getting stable (like 5 runs, no
>> problems).
>> 
>> So with the gaussian curve tail whipping ones behind (risque of 
>> failure) it
>> might need to be like 300 ms in my case... :-)
> 
> Pick a value that is high enough to be reliable and submit a patch to
> "net" where you present the evidence for it (top-level MDIO controller,
> SoC, switch, kernel). I don't believe there's much to read into. A 
> large
> timeout shouldn't have a negative effect on the MDIO performance,
> because it just determines how long it takes until the kernel declares
> it dead, rather than how long it takes for transactions to actually 
> take
> place.

Would it not be appropriate to have a define that specifies the value 
instead
of the same value two places as it is now?

And in so case, what would be an appropriate name?