Re: [PATCH net v3 0/2] net: dsa: b53: fix 8021q uppers on standalone ports

[Jonas Gorski]

Hi,

On Mon, Aug 31, 2026 at 10:52 AM Semih Baskan <strst.gs@xxxxxxxxx> wrote:
>
> Since v5.15, a standalone port on a bcm5301x b53 switch cannot receive
> its own tagged traffic: the switch VID lookup is always active, an 8021q
> upper's VID never reaches the VLAN table, and a tagged frame with a
> missing VID is forwarded only toward the IMP0 management port, which the
> in-tree bcm5301x topology leaves disabled, so it never reaches the CPU.
> The common victim is a VLAN-tagged PPPoE WAN, where the PADI goes out
> and the tagged PADO never reaches the CPU.

I really don't agree with the framing here. The subject essentially
claims that uppers don't work in general, but that is not true at all.
They don't work for devices with a *broken* device tree configuration.

So this is a work-around for broken configuration.

Also this is an incomplete fix, because it still won't work 100%, and
there is no way to fix this from within the driver, the device tree
needs to be fixed. E.g. with the (assumed) disabled EAP mode on
stand-alone ports, you will have the issue that the switch will drop
any frames with destination MACs that match a learned entry on a
bridged port.

I really think we should just fix up the in-tree device trees and then
complain loudly about the broken configuration on probe in case there
are out of tree device trees with the broken configuration. I mean it
was broken since v5.15 and wasn't noticed until recently, so it
doesn't seem affect many users.

Best regards,
Jonas