linux-kernel - Re: [PATCH] Revert "net: stmmac: Do not keep rearming the coalesce timer in stmmac

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Message-ID: <d3858ef0-97c7-28b5-db4a-4ac71af52ba5@synopsys.com>
Date:   Tue, 28 Aug 2018 09:12:33 +0100
From:   Jose Abreu <Jose.Abreu@...opsys.com>
To:     Jerome Brunet <jbrunet@...libre.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        "Jose Abreu" <Jose.Abreu@...opsys.com>, <netdev@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>,
        <linux-amlogic@...ts.infradead.org>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        Vitor Soares <Vitor.Soares@...opsys.com>,
        Corentin Labbe <clabbe@...libre.com>
Subject: Re: [PATCH] Revert "net: stmmac: Do not keep rearming the coalesce
 timer in stmmac_xmit"

Hi Jerome,

On 24-08-2018 10:04, Jerome Brunet wrote:
> This reverts commit 4ae0169fd1b3c792b66be58995b7e6b629919ecf.
>
> This change in the handling of the coalesce timer is causing regression on
> (at least) amlogic platforms.
>
> Network will break down very quickly (a few seconds) after starting
> a download. This can easily be reproduced using iperf3 for example.
>
> The problem has been reported on the S805, S905, S912 and A113 SoCs
> (Realtek and Micrel PHYs) and it is likely impacting all Amlogics
> platforms using Gbit ethernet
>
> No problem was seen with the platform using 10/100 only PHYs (GXL internal)
>
> Reverting change brings things back to normal and allows to use network
> again until we better understand the problem with the coalesce timer.
>
>

Apologies for the delayed answer but I was in FTO.

I'm not sure what can be causing this but I have some questions
for you:
    - What do you mean by "network will break down"? Do you see
queue timeout?
    - What do you see in ethtool/ifconfig stats? Can you send me
the stats before and after network break?
    - Is your setup multi-queue/channel?
    - Can you point me to the DT bindings of your setup?

Thanks and Best Regards,
Jose Miguel Abreu