From:   Xiaoliang Yang <xiaoliang.yang_1@nxp.com>
To:     Jakub Kicinski <kuba@kernel.org>,
        Joakim Zhang <qiangqing.zhang@nxp.com>
CC:     "davem@davemloft.net" <davem@davemloft.net>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "peppe.cavallaro@st.com" <peppe.cavallaro@st.com>,
        "alexandre.torgue@foss.st.com" <alexandre.torgue@foss.st.com>,
        "joabreu@synopsys.com" <joabreu@synopsys.com>,
        Yannick Vignon <yannick.vignon@nxp.com>,
        "boon.leong.ong@intel.com" <boon.leong.ong@intel.com>,
        "Jose.Abreu@synopsys.com" <Jose.Abreu@synopsys.com>,
        "mst@redhat.com" <mst@redhat.com>,
        "Joao.Pinto@synopsys.com" <Joao.Pinto@synopsys.com>,
        Mingkai Hu <mingkai.hu@nxp.com>, Leo Li <leoyang.li@nxp.com>
Subject: RE: [EXT] Re: [PATCH net-next] net: stmmac: bump tc when get
 underflow error from DMA descriptor
Thread-Topic: [EXT] Re: [PATCH net-next] net: stmmac: bump tc when get
 underflow error from DMA descriptor
Thread-Index: AQHX7Bmwj7VotTMrk0auLbMKkiRGRqwpYOIAgAGlwYCAAAEj4A==
Date:   Fri, 10 Dec 2021 03:11:16 +0000
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References: <20211208100651.19369-1-xiaoliang.yang_1@nxp.com>
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 <20211209184123.63117f42@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
In-Reply-To: <20211209184123.63117f42@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
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Hi Jakub,

On Fri, 10 Dec 2021 10:41:00 +0800 Jakub Kicinski wrote:
> > > net: stmmac: bump tc when get underflow error from DMA descriptor
> > >
> > > In DMA threshold mode, frame underflow errors may sometimes occur
> > > when the TC(threshold control) value is not enough. The TC value
> > > need to be bumped up in this case.
> > >
> > > There is no underflow interrupt bit on DMA_CH(#i)_Status of dwmac4,
> > > so the DMA threshold cannot be bumped up in stmmac_dma_interrupt().
> > > The i.mx8mp board observed an underflow error while running NFS
> > > boot, the NFS rootfs could not be mounted.
> > >
> > > The underflow error can be got from the DMA descriptor TDES3 on
> dwmac4.
> > > This patch bump up tc value once underflow error is got from TDES3.
> > >
> > > Signed-off-by: Xiaoliang Yang <xiaoliang.yang_1@nxp.com>
> >
> > 5 queues with FIFO cut-through mode can work well after applying this
> patch.
>=20
> This never worked, correct? It's not a regression fix?
Yes, it's never worked when the underflow error is observed in the case of =
NFS boot on i.mx8mp. I'm not sure if other SoC have same issue in this case=
, but I think it's necessary to increase the threshold value in case of und=
erflow error.
Do you mean that I need to send the patch as a bug fix to net branch?

Regards,
Xiaoliang