Re: [PATCH] net: dsa: qca8k: Disable mgmt Ethernet for qca8327

[Michał Kępień]

> > I came across this while migrating an AR9344-based router with a QCA8327
> > rev. 4 switch to a DSA-aware driver.  This glitch is a pain in the neck
> > to troubleshoot any further as it occurs randomly, anywhere between a
> > minute to an hour after the switch is set up; traffic load exerted on
> > the switch does not seem to matter as the problem can be triggered on a
> > virtually idle device.  Previously working links are reported as going
> > down (one by one, not all at once), even though port LEDs still blink;
> > no traffic is forwarded; reloading qca8k does not alleviate the problem,
> > only power cycling seems to help.  Nothing like this happens when only
> > MDIO is used.  However, qca8k currently only uses MDIO as a fallback.  I
> > figured that simpler is better and that mgmt Ethernet should simply be
> > disabled for the qca8327, but I would be happy to work on some
> > configurable solution if that would be preferable.
> >
> 
> This is a long standing issue and it seems to me disabling mgmt is just a
> big workaround to a real problem.

Understood.  Is it a long-standing issue for the QCA mgmt Ethernet code
in general or for a specific subset of switches (or devices)?

> Long time ago it was reported that there seems to be a problem with the
> mdio master register for external and internall access and how mgmt was
> actually sending mdio command... just done by the switch. Could the 2 issue
> related?

This thread?

https://lore.kernel.org/netdev/20250425151309.30493-1-kabel@xxxxxxxxxx/

If so, that was for QCA8337, on a board where the external MDIO bus has
an extra PHY attached, so it did not look like a match for my case.  Of
course, it _might_ be related to the issue I'm running into, it just did
not seem to be at first glance.

> One idea might be to verify that stuff gets actually written... as Andrew
> said to verify if some packets doesn't get lost or just ignored.

Ack.

> Also as Andrew said I would still save this for the MIB part as the 2 thing
> should be unrelated.

Got it, I'll play around with it and see what I can find out, thanks.

-- 
Best regards,
Michał Kępień