netdev - RE: [PATCH net-next 3/3] net: stmmac: Introducing support for Page Pool

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Date:   Sat, 27 Jul 2019 15:56:36 +0000
From:   Jose Abreu <Jose.Abreu@...opsys.com>
To:     Jon Hunter <jonathanh@...dia.com>,
        Jose Abreu <Jose.Abreu@...opsys.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
CC:     Joao Pinto <Joao.Pinto@...opsys.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Robin Murphy <robin.murphy@....com>,
        "David S . Miller" <davem@...emloft.net>
Subject: RE: [PATCH net-next 3/3] net: stmmac: Introducing support for Page
 Pool

From: Jon Hunter <jonathanh@...dia.com>
Date: Jul/26/2019, 15:11:00 (UTC+00:00)

> 
> On 25/07/2019 16:12, Jose Abreu wrote:
> > From: Jon Hunter <jonathanh@...dia.com>
> > Date: Jul/25/2019, 15:25:59 (UTC+00:00)
> > 
> >>
> >> On 25/07/2019 14:26, Jose Abreu wrote:
> >>
> >> ...
> >>
> >>> Well, I wasn't expecting that :/
> >>>
> >>> Per documentation of barriers I think we should set descriptor fields 
> >>> and then barrier and finally ownership to HW so that remaining fields 
> >>> are coherent before owner is set.
> >>>
> >>> Anyway, can you also add a dma_rmb() after the call to 
> >>> stmmac_rx_status() ?
> >>
> >> Yes. I removed the debug print added the barrier, but that did not help.
> > 
> > So, I was finally able to setup NFS using your replicated setup and I 
> > can't see the issue :(
> > 
> > The only difference I have from yours is that I'm using TCP in NFS 
> > whilst you (I believe from the logs), use UDP.
> 
> So I tried TCP by setting the kernel boot params to 'nfsvers=3' and
> 'proto=tcp' and this does appear to be more stable, but not 100% stable.
> It still appears to fail in the same place about 50% of the time.
> 
> > You do have flow control active right ? And your HW FIFO size is >= 4k ?
> 
> How can I verify if flow control is active?

You can check it by dumping register MTL_RxQ_Operation_Mode (0xd30).

Can you also add IOMMU debug in file "drivers/iommu/iommu.c" ?

---
Thanks,
Jose Miguel Abreu