netdev - Re: Need help with mdiobus

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Date:   Sat, 15 Oct 2016 12:19:22 +0200
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Andrew Lunn <andrew@...n.ch>, Timur Tabi <timur@...eaurora.org>
CC:     netdev@...r.kernel.org
Subject: Re: Need help with mdiobus_register and phy

On October 14, 2016 7:25:14 PM CEST, Andrew Lunn <andrew@...n.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.

-- 
Florian