> Hi Andrew,
>
> I don't have experience with Ethernet switch, according to your
> points, you mean we can connect STMMAC to an Ethernet switch, and
> then Ethernet switch managed STMMAC by the MDIO bus but without
> checking whether STMMAC interface is opened or not, so STMMAC needs
> clocks for MDIO even interface is closed, right?
Correct. The MDIO bus has a different life cycle to the MAC. If any of
stmmac_xgmac2_mdio_read(), stmmac_xgmac2_mdio_write(),
stmmac_mdio_read(), and stmmac_mdio_write() need clocks ticking, you
need to ensure the clock is ticking, because these functions can be
called while the interface is not opened.
> > You said you copied the FEC driver. Take a look at that, it was initially
> > broken in
> > this way, and i needed to extend it when i got a board with an Ethernet
> > switch
> > attached to the FEC.
>
> Could you point me how to implement clocks management to cover above
> Ethernet switch case? Or can we upstream this first and then fix it
> later for such case?
I actually got is wrong on the first attempt. So you need to look at:
42ea4457ae net: fec: normalize return value of pm_runtime_get_sync() in MDIO
write
14d2b7c1a9 net: fec: fix initial runtime PM refcount
8fff755e9f net: fec: Ensure clocks are enabled while using mdio bus
And no, you cannot fix it later, because your patches potentially
break existing systems using an Ethernet switch. See:
ommit da29f2d84bd10234df570b7f07cbd0166e738230
Author: Jose Abreu <jose.ab...@synopsys.com>
Date: Tue Jan 7 13:35:42 2020 +0100
net: stmmac: Fixed link does not need MDIO Bus
When using fixed link we don't need the MDIO bus support.
...
Tested-by: Florian Fainelli <f.fainelli@gmail> # Lamobo R1 (fixed-link +
MDIO sub node for roboswitch).
So there are boards which make use of a switch and MDIO. Florian might
however be able to run tests for you, if you ask him.
Andrew
