Re: [PATCH RFC net-next 2/3] net: dsa: mxl862xx: add SMDIO clause-22 register access

[Daniel Golle <daniel@makrotopia.org>]

On Thu, Jul 09, 2026 at 01:15:34AM +0200, Andrew Lunn wrote:
> On Wed, Jul 08, 2026 at 09:45:48PM +0200, Daniel Golle wrote:
> > On Wed, Jul 08, 2026 at 07:22:49PM +0200, Andrew Lunn wrote:
> > > On Tue, Jul 07, 2026 at 04:16:07PM +0200, Daniel Golle wrote:
> > > > Add mxl862xx_smdio_read() and mxl862xx_smdio_write() for clause-22
> > > > SMDIO register access. MCUboot rescue mode only exposes clause-22
> > > > registers; the existing clause-45 MMD interface is unavailable during
> > > > firmware transfer. The MDIO bus lock is held per-transaction (not
> > > > across polls) so that SB PDI polling during flash erase does not
> > > > starve other MDIO users.
> > > 
> > > What other MDIO users are there? It sounds like once the switch is in
> > > rescue mode, switch management is dead. So how can there be users?
> > 
> > The MDIO bus lock refers to the host bus which is used to connect
> > the switch management interface. The same bus can also be used to
> > connect other unrelated PHYs (eg. to provide a WAN or management
> > interface independent of the switch).
> 
> Thanks for the explanation. Maybe 'does not starve other non-switch
> MDIO users'?
> 
> I've not got to the rest of the patch yet, but i wondered if phylib
> might still be trying to poll the switches PHYs.

The driver takes down the CPU ports and thereby implicitely also puts
all user-ports into admin-down state, effectively disabling PHY polling
until the switch comes back and reprobe has happened.