Re: [PATCH 0/3] Fix for KSZ DSA switch shutdown

On Fri, Sep 10, 2021 at 05:58:52PM +0300, Vladimir Oltean wrote:

On Fri, Sep 10, 2021 at 01:51:56PM +0200, Andrew Lunn wrote:

quoted

quoted

It does not really scale but we also don't have that many DSA masters to
support, I believe I can name them all: bcmgenet, stmmac, bcmsysport, enetc,
mv643xx_eth, cpsw, macb.

fec, mvneta, mvpp2, i210/igb.

I can probably double that list only with Freescale/NXP Ethernet
drivers, some of which are not even submitted to mainline. To name some
mainline drivers: gianfar, dpaa-eth, dpaa2-eth, dpaa2-switch, ucc_geth.
Also consider that DSA/switchdev drivers can also be DSA masters of
their own, we have boards doing that too.

Anyway, I've decided to at least try and accept the fact that DSA
masters will unregister their net_device on shutdown, and attempt to do
something sane for all DSA switches in that case.

Attached are two patches (they are fairly big so I won't paste them
inline, and I would like initial feedback before posting them to the
list).

As mentioned in those patches, the shutdown ordering guarantee is still
very important, I still have no clue what goes on there, what we need to
do, etc.

So to answer my own question, there is a comment above device_link_add:

 * A side effect of the link creation is re-ordering of dpm_list and the
 * devices_kset list by moving the consumer device and all devices depending
 * on it to the ends of these lists (that does not happen to devices that have
 * not been registered when this function is called).

so the fact that DSA uses device_link_add towards its master is not
exactly for nothing. device_shutdown() walks devices_kset from the back,
so this is our guarantee that DSA's shutdown happens before the master's
shutdown.

So these patches should be okay. Any other comments? If not, I will
formally submit them tomorrow towards the net tree.