linux-kernel - Re: Regression v5.12-rc3: net: stmmac: re-init rx buffers when mac resume back

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Message-ID: <85f02fbc-6956-2b19-1779-cd51b2e71e3d@nvidia.com>
Date:   Wed, 31 Mar 2021 12:29:01 +0100
From:   Jon Hunter <jonathanh@...dia.com>
To:     Joakim Zhang <qiangqing.zhang@....com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Jose Abreu <joabreu@...opsys.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        Jakub Kicinski <kuba@...nel.org>
Subject: Re: Regression v5.12-rc3: net: stmmac: re-init rx buffers when mac
 resume back


On 31/03/2021 12:10, Joakim Zhang wrote:

...

>>>>>>>> You mean one of your boards? Does other boards with STMMAC can
>>>>>>>> work
>>>>>>> fine?
>>>>>>>
>>>>>>> We have two devices with the STMMAC and one works OK and the
>>>>>>> other
>>>>> fails.
>>>>>>> They are different generation of device and so there could be
>>>>>>> some architectural differences which is causing this to only be
>>>>>>> seen on one
>>> device.
>>>>>> It's really strange, but I also don't know what architectural
>>>>>> differences could
>>>>> affect this. Sorry.
>>>
>>>
>>> I realised that for the board which fails after this change is made,
>>> it has the IOMMU enabled. The other board does not at the moment
>>> (although work is in progress to enable). If I add
>>> 'iommu.passthrough=1' to cmdline for the failing board, then it works
>>> again. So in my case, the problem is linked to the IOMMU being enabled.
>>>
>>> Does you platform enable the IOMMU?
>>
>> Hi Jon,
>>
>> There is no IOMMU hardware available on our boards. But why IOMMU would
>> affect it during suspend/resume, and no problem in normal mode?
> 
> One more add, I saw drivers/iommu/tegra-gart.c(not sure if is this) support suspend/resume, is it possible iommu resume back after stmmac?


This board is the tegra186-p2771-0000 (Jetson TX2) and uses the
arm,mmu-500 and not the above driver.

In answer to your question, resuming from suspend does work on this
board without your change. We have been testing suspend/resume now on
this board since Linux v5.8 and so we have the ability to bisect such
regressions. So it is clear to me that this is the change that caused
this, but I am not sure why.

Thanks
Jon

-- 
nvpublic