Re: [PATCH v1 1/2] driver core: fw_devlink: Add support for FWNODE_FLAG_BROKEN_PARENT

On 9/30/21 12:48 PM, Saravana Kannan wrote:

On Thu, Sep 30, 2021 at 12:38 PM Andrew Lunn [off-list ref] wrote:

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Btw, do we have non-DSA networking devices where fw_devlink=on
delaying PHY probes is causing an issue?

I don't know if issues have been reported, but the realtek driver has
had problems in the past when the generic driver is used. Take a look
at r8169_mdio_register(), it does something similar to DSA.

Does it have the issue of having the PHY as its child too and then
depending on it to bind to a driver? I can't tell because I didn't
know how to find that info for a PCI device.

Yes, r8169 includes a MDIO bus controller, and the PHY is internal to
the Ethernet MAC. These are AFAIR the relevant changes to this discussion:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=16983507742cbcaa5592af530872a82e82fb9c51
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=11287b693d03830010356339e4ceddf47dee34fa

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What is going to make things interesting is that phy_attach_direct()
is called in two different contexts. During the MAC drivers probe, it
is O.K. to return EPROBE_DEFER, and let the MAC driver try again
later, if we know there is a specific PHY driver for it. But when
called during the MAC drivers open() op, -EPROBE_DEFER is not
allowed. What to do then is an interesting question.

Yeah, basically before doing an open() it'll have to call an API to
say "just bind with whatever you got". Or something along those lines.
I already know how to get that to work. I'll send some RFC soonish (I
hope).

I don't think this is going to scale, we have dozens and dozens of
drivers that connect to the PHY during ndo_open(). It is not realistic
to audit them all, just like the opposite case where the drivers do
probe MDIO/PHY during their .probe() call is not realistic either.
-- 
Florian