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

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Date:   Tue, 15 Nov 2022 17:03:01 +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 2022-11-15 15:56, Vladimir Oltean wrote:
> On Tue, Nov 15, 2022 at 02:25:13PM +0100, netdev@...io-technology.com 
> wrote:
>> On 2022-11-15 13:22, Vladimir Oltean wrote:
>> > Do you have a timeline for when the regression was introduced?
>> > Commit 35da1dfd9484 reverts cleanly, so I suppose giving it a go with
>> > that reverted might be worth a shot. Otherwise, a bisect from a known
>> > working version only takes a couple of hours, and shouldn't require
>> > other changes to the setup.
>> 
>> Wow! Reverting 35da1dfd9484 and the problem has disappeared. :-)
> 
> See? That wasn't very painful, was it.

Indeed it was not, when you get a good tip. Thanks alot! :-)

> 
> Now, why doesn't that commit work for you? that's the real question.
> I'm going to say there's a big assumption made there. The old code used
> to poll up to 16 times with sleeps of up to 2 ms in between.
> The new code polls until at least 50 ms have elapsed.
> I can imagine the thought process being something like "hmm, 16*2=32ms,
> let's round that up to 50 just to be sure". But the effective timeout
> was not really increased. Rather said, in the old code there was never
> really an effective timeout, since the polling code could have been
> preempted many times, and these preemptions would not be accounted
> against the msleep(2) calls. Whereas the new code really tracks
> something approximating 50 ms now.
> 
> Could you please add the reverted patch back to your git tree, and see
> by how much do you need to increase the timeout for your system to get
> reliable results?
> 

Yes, so you want me to simply increase the 50ms on line 58 in smi.c...

I have now tried to increase it even to 10000ms == 10s and it didn't 
help,
so something else must be needed...