Help with testing needed [Was: Re: [PATCH 1/3] ramips: ethernet: ralink: mt7620 jumbo frame support]

Luiz Angelo Daros de Luca luizluca at
Wed Mar 30 22:37:22 PDT 2022

 > >
> > Hi Andrey,
> >
> > > It simple a) don't apply to master tree; b) not working - MAX_RX_LENGTH constant not
> > > touched, GSW_REG_GMACCR not tweaked for accepting jumbo frames.
> >
> > a) Sorry, I missed your answer and thanks for the review. Yes, it was
> > not applying to master. It was based on another patch deeper in my
> > tree. I fixed that a long time ago but I postponed the fix as I didn't
> > see any interest from ML (I was wrong). I was focusing on upstream
> > patches (realtek dsa switches merged into 5.18) and postponed the
> > ramips fixes for when they would be needed.
> >
> > b) MAX_RX_LENGTH seems to be used only for keeping the buffer at least
> > over (MAX_RX_LENGTH - FE_RX_ETH_HLEN) and it does not care when mtu is
> > actually even bigger than (MAX_RX_LENGTH - FE_RX_ETH_HLEN). See:
> MAX_RX_LENGTH affects buffers for DMA transfers.

Is it because when you unconditionally enable jumbo frames in switch,
you need to prepare the ethernet driver to receive a larger frame,
even when mtu is 1500 or smaller?

> > c) MAX_RX_JUMBO and MAX_RX_PKT_LEN in GSW_REG_GMACCR are switch regs
> > while I touched only ethernet frame engine regs.
> There are two parts - FE and switch. And both need to be properly programmed.
> Attached patch tested on real MT7620 with internal switch and it is
> able to operate with a 2048-bytes frame (included single VLAN tag).

Are you ignoring CONFIG_SOC_MT7621 support for this driver? (it is
indeed upstream for recent kernels).

The patch worked as expected! Thanks a lot! Do you plan to submit it?

Tested-by: Luiz Angelo Daros de Luca <luizluca at>

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