[RFC PATCH net-next 0/9] net: pcs: Add support for devices probed in the "usual" manner

[Sean Anderson]

On 7/19/22 11:38 AM, Vladimir Oltean wrote:
> On Tue, Jul 19, 2022 at 11:28:42AM -0400, Sean Anderson wrote:
>> Hi Vladimir,
>> 
>> On 7/19/22 11:25 AM, Vladimir Oltean wrote:
>> > Hi Sean,
>> > 
>> > On Mon, Jul 11, 2022 at 12:05:10PM -0400, Sean Anderson wrote:
>> >> For a long time, PCSs have been tightly coupled with their MACs. For
>> >> this reason, the MAC creates the "phy" or mdio device, and then passes
>> >> it to the PCS to initialize. This has a few disadvantages:
>> >> 
>> >> - Each MAC must re-implement the same steps to look up/create a PCS
>> >> - The PCS cannot use functions tied to device lifetime, such as devm_*.
>> >> - Generally, the PCS does not have easy access to its device tree node
>> >> 
>> >> I'm not sure if these are terribly large disadvantages. In fact, I'm not
>> >> sure if this series provides any benefit which could not be achieved
>> >> with judicious use of helper functions. In any case, here it is.
>> >> 
>> >> NB: Several (later) patches in this series should not be applied. See
>> >> the notes in each commit for details on when they can be applied.
>> > 
>> > Sorry to burst your bubble, but the networking drivers on NXP LS1028A
>> > (device tree at arch/arm64/boot/dts/freescale/fsl-ls1028a.dtsi, drivers
>> > at drivers/net/ethernet/freescale/enetc/ and drivers/net/dsa/ocelot/)
>> > do not use the Lynx PCS through a pcs-handle, because the Lynx PCS in
>> > fact has no backing OF node there, nor do the internal MDIO buses of the
>> > ENETC and of the switch.
>> > 
>> > It seems that I need to point this out explicitly: you need to provide
>> > at least a working migration path to your PCS driver model. Currently
>> > there isn't one, and as a result, networking is broken on the LS1028A
>> > with this patch set.
>> > 
>> 
>> Please refer to patches 4, 5, and 6.
> 
> I don't understand, could you be more clear? Are you saying that I
> shouldn't have applied patch 9 while testing? When would be a good
> moment to apply patch 9?

I'm saying that patches 4 and 5 [1] provide "...a working migration
path to [my] PCS driver model." Since enetc/ocelot do not use
devicetree for the PCS, patch 9 should have no effect.

That said, if you've tested this on actual hardware, I'm interested
in your results. I do not have access to enetc/ocelot hardware, so
I was unable to test whether my proposed migration would work.

--Sean

[1] I listed 6 but it seems like it just has some small hunks which should have been in 5 instead