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

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Date:   Fri, 1 Dec 2017 15:49:48 +0000
From:   Bhadram Varka <vbhadram@...dia.com>
To:     "Lars P (Mailing List Account)" <lists@...h.nu>
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 Lars,

> -----Original Message-----
> From: netdev-owner@...r.kernel.org [mailto:netdev-
> owner@...r.kernel.org] On Behalf Of Lars P (Mailing List Account)
> Sent: Friday, December 01, 2017 9:05 PM
> To: Bhadram Varka <vbhadram@...dia.com>
> Cc: Joao.Pinto@...opsys.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 ?

Yes. TSO enabled for 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.

I believe it would be better we can make the MSS on per queue basis instead of getting through global variable.

Thanks,
Bhadram.
> 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.
> >

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