RE: [PATCH net] net: lan743x: permit VLAN-tagged packets up to configured MTU

[David Thompson]

> -----Original Message-----
> From: Jakub Kicinski <kuba@xxxxxxxxxx>
> Sent: Tuesday, May 19, 2026 9:31 PM
> To: David Thompson <davthompson@xxxxxxxxxx>
> Cc: bryan.whitehead@xxxxxxxxxxxxx; UNGLinuxDriver@xxxxxxxxxxxxx;
> andrew+netdev@xxxxxxx; davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx;
> pabeni@xxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH net] net: lan743x: permit VLAN-tagged packets up to
> configured MTU
> 
> On Fri, 15 May 2026 19:23:57 +0000 David Thompson wrote:
> > The driver must set the MAC_RX.FSE bit before setting MAC_RX.RXEN to
> > allow VLAN-tagged frames up to the interface MTU
> 
> AFAIU this sentence indicates that the double write is intentional but could you
> make that more explicit?
> Maybe mention whether this is based on experience or the AN?
> 
> It's going to be invaluable if someone ever sends a "cleanup"
> to fold the writes into one..
> 
> >  	temp = lan743x_csr_read(adapter, MAC_RX);
> > +	temp |= MAC_RX_FSE_;
> > +	lan743x_csr_write(adapter, MAC_RX, temp);
> >  	lan743x_csr_write(adapter, MAC_RX, temp | MAC_RX_RXEN_);
> --
> pw-bot: cr

Thank you for the review, Jakub.

Yes, this second write is intentional per Application Note 2948.

I will add a comment to clarify this and post a v2.

- Dave