Re: [PATCH net-next v15 07/13] net: mdio: realtek-rtl9300: Configure hardware polling during probing

[Andrew Lunn <andrew@lunn.ch>]

On Mon, Aug 31, 2026 at 04:34:33PM +0200, Markus Stockhausen wrote:
> During PHY probing and configuration complex configuration sequences
> might be issued and firmware might be loaded. Hardware polling can
> interfere badly with that. E.g. a hardware polling MMD c45 over c22
> request might break an ongoing firmware loading sequence.
> 
> To avoid such issues the polling of the Realtek Otto switches can be
> (de)activated with one or two 32 bit mask registers. Each bit enables
> (=1) or disables (=0) the polling of the corresponding port. Make use
> of this as follows:
> 
> - Disable polling for all ports when the MDIO driver starts.
> - Reenable polling just after the PHY has been attached.
> - Disable polling just before the PHY is being detached.
> 
> This synchronizes the kernel and hardware polling to some extent. It
> gracefully handles deferred probing of PHYs in case the driver is
> loaded asynchronously during boot. Additionally it brings the hardware
> polling into a consistent operation mode for devices where U-Boot does
> not take care.
> 
> Important notes about the implementation:
> 
> Realtek is very inconsistent about its register naming. RTL930x uses
> SMI_POLL_CTRL for polling control while it is SMI_PORT_POLLING_CTRL
> on RTL931x. Keep these vendor names.
> 
> These devices do not support power management for the whole system.
> So mdio_bus_phy_resume() is not used and it is not required to
> disable/enable hardware polling for that usecase.
> 
> These devices have no CPU MAC to PHY design. Thus abort phy_attach()
> in case PHYs are not mapped to valid switch ports. All MDIO bus
> commands will fail afterwards, leaving it in an unusable state.
> 
> Enabling/disabling hardware polling is a simple regmap bit access.
> For this it is enough to rely on the regmap internal lock.
> 
> This polling enabling/disabling does not solve the current inability
> of the driver to handle C45-over-C22 access during normal operation.
> For all existing designs this is not needed.
> 
> [1] https://github.com/openwrt/openwrt/blob/main/target/linux/realtek/files-6.18/drivers/net/mdio/mdio-realtek-otto.c#L818
> [2] https://lore.kernel.org/netdev/680696024a8648535ce6dee771fe4de67802e0e8.1769053496.git.daniel@makrotopia.org/
> 
> Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew