netdev - Re: [RFC PATCH 0/2] net: macb: Disable TX checksum offloading on all Zynq

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Date:   Wed, 1 Aug 2018 18:23:41 +0530
From:   Harini Katakam <harinik@...inx.com>
To:     Jennifer Dahm <jennifer.dahm@...com>
Cc:     netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>,
        Nathan Sullivan <nathan.sullivan@...com>,
        Rafal Ozieblo <rafalo@...ence.com>,
        Claudiu Beznea <Claudiu.Beznea@...rochip.com>,
        Harini Katakam <harini.katakam@...inx.com>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>
Subject: Re: [RFC PATCH 0/2] net: macb: Disable TX checksum offloading on all Zynq

Hi Jennifer,

On Tue, Jun 5, 2018 at 10:21 AM, Harini Katakam <harinik@...inx.com> wrote:
> Hi Jeniffer,
>
> On Mon, Jun 4, 2018 at 8:35 PM, Nicolas Ferre
> <nicolas.ferre@...rochip.com> wrote:
>> Jennifer,
>>
>> On 25/05/2018 at 23:44, Jennifer Dahm wrote:
>>>
>>> During testing, I discovered that the Zynq GEM hardware overwrites all
>>> outgoing UDP packet checksums, which is illegal in packet forwarding
>>> cases. This happens both with and without the checksum-zeroing
>>> behavior  introduced  in  007e4ba3ee137f4700f39aa6dbaf01a71047c5f6
>>> ("net: macb: initialize checksum when using checksum offloading"). The
>>> only solution to both the small packet bug and the packet forwarding
>>> bug that I can find is to disable TX checksum offloading entirely.
>>
>>
>
> Thanks for the extensive testing.
> I'll try to reproduce and see if it is something to be fixed in the driver.
>
>> Are the bugs listed above present in all revisions of the GEM IP, only for
>> some revisions?
>> Is there an errata that describe this issue for the Zynq GEM?
>
> @Nicolas, AFAIK, there is no errata for this in either Cadence or
> Zynq documentation.

I was unable to reproduce this issue on Zynq.
Although I do not have HW with two GEM ports,
I tried by routing one GEM via PL and another via on board RGMII.
Since there was no specific errata related to this, I also tried on
subsequent ZynqMP versions with multiple GEM ports but dint find any
checksum issues. I discussed the same with cadence and they
tried the test with 2 bytes of UDP payload on the Zynq GEM IP
version in their regressions and did not hit any issue either.

I tried to reach out earlier to see if you can share your exact
application. Could you please let me know if you have any
further updates?

Regards,
Harini