netdev - Re: stmmac / meson8b-dwmac

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Date:   Sat, 11 May 2019 16:53:34 +0200
From:   Simon Huelck <simonmail@....de>
To:     Jose Abreu <jose.abreu@...opsys.com>,
        Sebastian Gottschall <s.gottschall@...media-net.de>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     linux-amlogic@...ts.infradead.org, Gpeppe.cavallaro@...com,
        alexandre.torgue@...com,
        Emiliano Ingrassia <ingrassia@...genesys.com>,
        netdev@...r.kernel.org
Subject: Re: stmmac / meson8b-dwmac

Hi guys,

on 5.1+ the story keeps being the same.

950 Mbits in each direction, but when in duplex RX is starving to ~70
MBits..

ethtool -S gave me some counts for mmc_rx_fifo_overflow, which i didnt
recognize before.


Do we have new ideas / new direction to dig for ?


regards,
Simon

Am 01.03.2019 um 10:23 schrieb Jose Abreu:
> Hi Simon,
>
> On 2/27/2019 7:02 PM, Simon Huelck wrote:
>> Hi,
>>
>>
>> the thing is , that im not a stmmac developer. Yes , maybe i can bissect
>> it and yes you are lucky since im a C-developer since a long time for
>> embedded systems.
>>
>> The problem is that i dont understand the structure of stmmac and im not
>> aware of any documentation about the driver structure nor the underlying
>> ethernet hardware ( even though im used to ethernet hardware in embedded
>> environment ). So how shall i recognize the relevant change between
>> 4.14.29 and 5.0rc8 ?
>>
>>
>> Is it in the DTS/DTB, wrong hardware description ? Is it in the code ?
>> how is the duplex hardware working on this piece ?
>>
>> I can try to support you the best i can, but i have little chances to
>> analyze it myself. At which measurements / counters is it possible to
>> see that duplex is fully working ?  Why did even the non-duplex
>> bandwidth regress from 900MBits to 650 ? Why is that 650 MBits dividing
>> up to TX and RX in summary when doing duplex ? Why is TX not starving in
>> duplex but RX ?
>>
>> From my point of view should be the following things given:
>> - the non duplex bandwidth should be somewhere around 900MBits , the HW
>> is capable of that
>> - TX should not influence RX or vice versa in duplex
>> - the duplex bandwidth should be 900MBits in both directions ( maybe a
>> bit asymetric when buffers in both dirs are not same )
>>
>> I guess we need some profiling on stmmac and ( at least i need ) more
>> knowledge of the hardware and stmmac itself. Can someone point me to the
>> driver documentation, describing the functions in the code and the
>> structure ? How can i profile stmmac ( usually im using hardware / JTAG
>> debuggers at work, but here @home i got nothing like that )
>>
>> So how do we continue ?
> When I said bissect I was meaning GIT Bissect [1]. You shouldn't
> need any development background for this. You just have to start
> bissect, compile, test and check if commit is good or not.
>
> I'm not very familiar with this feature but I think you can
> bissect pretty fast if you say you just want stmmac commits,
> check ("Cutting down bisection by giving more parameters to
> bisect start") on previous link ... In your case it would be
> stmmac changes, dts, and phy.
>
> [1] https://git-scm.com/docs/git-bisect
>
> Thanks,
> Jose Miguel Abreu