netdev - Re: NETDEV WATCHDOG: eth0 (dwc-eth-dwmac): transmit queue 1 timed out

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Message-ID: <CADnJP=uxr=tfpP26Z2b6g--TK1cX+f3Qf=W0Q9HmezfHXVXfhQ@mail.gmail.com>
Date:   Fri, 1 Dec 2017 16:34:57 +0100
From:   "Lars P (Mailing List Account)" <lists@...h.nu>
To:     Bhadram Varka <vbhadram@...dia.com>
Cc:     "Joao.Pinto@...opsys.com" <Joao.Pinto@...opsys.com>,
        "peppe.cavallaro@...com" <peppe.cavallaro@...com>,
        linux-netdev <netdev@...r.kernel.org>
Subject: Re: NETDEV WATCHDOG: eth0 (dwc-eth-dwmac): transmit queue 1 timed out

Hi Bhadram,

Does the Tegra by any chance have TSO enabled on multiple TX-DMA channels ?

I recently noticed a second TSO bug in the stmmac while making the
patch "stmmac: reset last TSO segment size after device open".

The last-used MSS setting in TSO is tracked as a device-global
variable and not per TX queue. Using TSO on tx queue 0 will record mss
to priv->mss and if we later use TSO on tx queue 1 with the same
gso_size then the driver will not use a context descriptor to set the
MSS size for this queue. This probably means that the TSO controller
in channel 1 goes nuts with an undefined mss setting.

BR,
 Lars Persson

On Mon, Nov 20, 2017 at 7:38 AM, Bhadram Varka <vbhadram@...dia.com> wrote:
> Hi Joao/Peppe,
>
> Observed this issue more frequently with multi-channel case. Am I missing something in DT ?
> Please help here to understand the issue.
>
> Thanks,
> Bhadram
>
> -----Original Message-----
> From: Bhadram Varka
> Sent: Thursday, November 16, 2017 9:41 AM
> To: linux-netdev <netdev@...r.kernel.org>
> Subject: NETDEV WATCHDOG: eth0 (dwc-eth-dwmac): transmit queue 1 timed out
>
> Hi,
>
> I am trying to enable multi-queue in Tegra186 EQOS (which has support for 4 channels). Observed below netdev watchdog warning. Its easily reproable with iperf test.
> In normal ping scenario this is not observed. I did not observe any issue if we disable TSO. Looks like issue in stmmac_tso_xmit() in multi-channel scenario.
>