On October 14, 2016 7:25:14 PM CEST, Andrew Lunn <and...@lunn.ch> wrote:

>> So after calling BMCR_PDOWN, the PHYSID1 and PHYSID2 registers are
>> no longer readable.  Is that expected?
>You are making two changes here. Is it the SGMII power down which is
>causing the id registers to return 0xffff, or the BMCR_PDOWN.

I would be curious to know about that as well.

>The generic suspend code sets the PDOWN bit, so it is assuming the PHY
>will respond afterwards.

After reading the spec again, it does not appear to me that a PHY with PDOWN 
set is guaranteed or even required to respond to other register reads such as 
MII_PHYID1/2, in which case we may have to implement a MDIO bus reset routine 
which clears PDOWN for all PHYs that we detect(ed), or as Andrew suggested, 
utilize the matching by compatible string with the PHY OUI in it.


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