Re: [PATCH v2 net-next 12/15] net: ethernet: mtk_eth_soc: introduce MTK_NETSYS_V2 support

Jakub Kicinski
2022-05-18T15:47:48Z

On Wed, 18 May 2022 11:53:12 +0200 Lorenzo Bianconi wrote:
> > > + WRITE_ONCE(desc->txd7, 0);
> > > + WRITE_ONCE(desc->txd8, 0);
> >
> > Why all the WRITE_ONCE()? Don't you just need a barrier between writing
> > the descriptor and kicking the HW?
>
> I used this approach just to be aligned with current codebase:
> https://github.com/torvalds/linux/blob/master/drivers/net/ethernet/mediatek/mtk_eth_soc.c#L1006
> https://github.com/torvalds/linux/blob/master/drivers/net/ethernet/mediatek/mtk_eth_soc.c#L1031
>
> but I guess we can even convert the code to use barrier instead. Agree?

Oh, I didn't realize. No preference on converting the old code
but it looks like a cargo cult to me so in the new code let's
not WRITE_ONCE() all descriptor writes unless there's a reason.