netdev - Re: [PATCH net-next] net: phy: continue searching for C45 MMDs even if first returned ffff:ffff

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Message-ID: <20200716205137.goazvzvhie5s7ttl@skbuf>
Date:   Thu, 16 Jul 2020 23:51:37 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     davem@...emloft.net, netdev@...r.kernel.org, linux@...linux.org.uk,
        f.fainelli@...il.com, hkallweit1@...il.com, claudiu.manoil@....com,
        alexandru.marginean@....com, ioana.ciornei@....com,
        michael@...le.cc
Subject: Re: [PATCH net-next] net: phy: continue searching for C45 MMDs even
 if first returned ffff:ffff

On Thu, Jul 16, 2020 at 10:12:10PM +0200, Andrew Lunn wrote:
> > Then the rest of the code just carried on thinking "ok, MMD 1 (PMA/PMD)
> > says that there are 31 devices in that package, each having a device id
> > of ffff:ffff, that's perfectly fine, let's go ahead and probe this PHY
> > device".
> 
> With a device ID of ffff:ffff, what PHY driver was getting loaded?
> 

You mean ffff:fffe.
No PHY driver. I am driving this PCS locally from within
drivers/net/dsa/ocelot/felix_vsc9959.c. I call get_phy_device at the
address where I know a PCS is present, for the simple reason that I like
an extra validation that my internal MDIO reads/writes are going
somewhere. I've had situations in the past where the PCS was working
because the bootloader had initialized it, however the internal MDIO
reads/writes from Linux were broken. So, the fact that get_phy_device
can read the PHY ID correctly is giving me some assurance.

> > - MDIO_DEVS1=0x008a, MDIO_DEVS2=0x0000,
> > - MDIO_DEVID1=0x0083, MDIO_DEVID2=0xe400
> 
> Now that we have valid IDs, is the same driver getting loaded? Do this
> ID adding somewhere?
> 

Not applicable, see above.

> > Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> 
> Reviewed-by: Andrew Lunn <andrew@...n.ch>
> 
>     Andrew

Thanks,
-Vladimir