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

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Date:   Thu, 25 Mar 2021 08:12:58 +0000
From:   Joakim Zhang <qiangqing.zhang@....com>
To:     Jon Hunter <jonathanh@...dia.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


> -----Original Message-----
> From: Jon Hunter <jonathanh@...dia.com>
> Sent: 2021年3月25日 16:01
> To: Joakim Zhang <qiangqing.zhang@....com>
> Cc: 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 25/03/2021 07:53, Joakim Zhang wrote:
> >
> >> -----Original Message-----
> >> From: Jon Hunter <jonathanh@...dia.com>
> >> Sent: 2021年3月24日 20:39
> >> To: Joakim Zhang <qiangqing.zhang@....com>
> >> Cc: 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 24/03/2021 12:20, Joakim Zhang wrote:
> >>
> >> ...
> >>
> >>> Sorry for this breakage at your side.
> >>>
> >>> 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.
> 
> 
> Maybe caching somewhere? In other words, could there be any cache flushing
> that we are missing here?
Have no idea, have not account into such case.

> >>> We do daily test with NFS to mount rootfs, on issue found. And I add
> >>> this
> >> patch at the resume patch, and on error check, this should not break
> suspend.
> >>> I even did the overnight stress test, there is no issue found.
> >>>
> >>> Could you please do more test to see where the issue happen?
> >>
> >> The issue occurs 100% of the time on the failing board and always on
> >> the first resume from suspend. Is there any more debug I can enable
> >> to track down what the problem is?
> >>
> >
> > As commit messages described, the patch aims to re-init rx buffers
> > address, since the address is not fixed, so I only can recycle and then
> re-allocate all of them. The page pool is allocated once when open the net
> device.
> >
> > Could you please debug if it fails at some functions, such as
> page_pool_dev_alloc_pages() ?
> 
> 
> Yes that was the first thing I tried, but no obvious failures from allocating the
> pools.
> 
> Are you certain that the problem you are seeing, that is being fixed by this
> change, is generic to all devices? The commit message states that 'descriptor
> write back by DMA could exhibit unusual behavior', is this a known issue in the
> STMMAC controller? If so does this impact all versions and what is the actual
> problem?

Yes, I confirm this patch fix issue at my side. It should not be a generic, it can reproduce at one of our boards.
To be honest, I have not found the root cause, this should be a workaround, I upstream it since I think it will not affect others which don't suffer from this.

Best Regards,
Joakim Zhang
> Jon
> 
> --
> nvpublic