[RFC PATCH net 4/5] net: dsa: microchip: ksz8863: be compatible with masters which unregister on shutdown

[Florian Fainelli]

On 9/12/2021 5:09 AM, Vladimir Oltean wrote:
> Since commit 2f1e8ea726e9 ("net: dsa: link interfaces with the DSA
> master to get rid of lockdep warnings"), DSA gained a requirement which
> it did not fulfill, which is to unlink itself from the DSA master at
> shutdown time.
> 
> Since the Microchip sub-driver for KSZ8863 was introduced after the bad
> commit, it has never worked with DSA masters which decide to unregister
> their net_device on shutdown, effectively hanging the reboot process.
> To fix that, we need to call dsa_switch_shutdown.
> 
> Since this driver expects the MDIO bus to be backed by mdio_bitbang, I
> don't think there is currently any MDIO bus driver which implements its
> ->shutdown by redirecting it to ->remove, but in any case, to be
> compatible with that pattern, it is necessary to implement an "if this
> then not that" scheme, to avoid ->remove and ->shutdown from being
> called both for the same struct device.
> 
> Fixes: 60a364760002 ("net: dsa: microchip: Add Microchip KSZ8863 SMI based driver support")
> Link: https://lore.kernel.org/netdev/20210909095324.12978-1-LinoSanfilippo@gmx.de/
> Reported-by: Lino Sanfilippo <LinoSanfilippo at gmx.de>
> Signed-off-by: Vladimir Oltean <vladimir.oltean at nxp.com>

Reviewed-by: Florian Fainelli <f.fainelli at gmail.com>
-- 
Florian