netdev - Re: [PATCH net-next] net: phy: avoid unneeded MDIO reads in genphy_read

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Date:   Thu, 25 Apr 2019 00:41:41 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        David Miller <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] net: phy: avoid unneeded MDIO reads in
 genphy_read_status

On Wed, Apr 24, 2019 at 09:49:30PM +0200, Heiner Kallweit wrote:
> Considering that in polling mode each link drop will be latched,
> settings can't have changed if link was up and is up.

Hi Heiner

What about the case of the PHY performing a downshift?

Could it be up, then finds a pair fails, so performs a downshift. Does
it always report link down and then up to the new speed? Or could it
just shift down? And so we want to read the new speed?

I suppose it could also perform an upshift? A broken pair comes back
to life, so it returns to the higher speed?

   Andrew