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

[Jakub Kicinski]

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@xxxxxxx>  
> 
> 5 queues with FIFO cut-through mode can work well after applying this patch.

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