linux-kernel - Re: [PATCH net-next] net: stmmac: bump tc when get underflow error from DMA descriptor

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Date:   Thu, 9 Dec 2021 18:41:23 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Joakim Zhang <qiangqing.zhang@....com>,
        Xiaoliang Yang <xiaoliang.yang_1@....com>
Cc:     "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "peppe.cavallaro@...com" <peppe.cavallaro@...com>,
        "alexandre.torgue@...s.st.com" <alexandre.torgue@...s.st.com>,
        "joabreu@...opsys.com" <joabreu@...opsys.com>,
        Yannick Vignon <yannick.vignon@....com>,
        "boon.leong.ong@...el.com" <boon.leong.ong@...el.com>,
        "Jose.Abreu@...opsys.com" <Jose.Abreu@...opsys.com>,
        "mst@...hat.com" <mst@...hat.com>,
        "sonic.zhang@...log.com" <sonic.zhang@...log.com>,
        "Joao.Pinto@...opsys.com" <Joao.Pinto@...opsys.com>,
        Mingkai Hu <mingkai.hu@....com>, Leo Li <leoyang.li@....com>
Subject: Re: [PATCH net-next] net: stmmac: bump tc when get underflow error
 from DMA descriptor

On Thu, 9 Dec 2021 01:31:52 +0000 Joakim Zhang 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@....com>  
> 
> 5 queues with FIFO cut-through mode can work well after applying this patch.

This never worked, correct? It's not a regression fix?