linux-kernel - Re: [PATCH net-next 10/11] net: dsa: mv88e6xxx: remove EEE support

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Date:   Tue, 1 Aug 2017 11:53:14 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...oirfairelinux.com,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH net-next 10/11] net: dsa: mv88e6xxx: remove EEE support

On 08/01/2017 10:27 AM, Andrew Lunn wrote:
>> If the MAC does not support EEE but the PHY does I think you can still
>> allow EEE to be advertised and enabled, you just won't have the MAC be
>> able to leverage the power savings that EEE brings. AFAICT this is still
>> a valid mode whereby the PHY is put in a lower power mode, just not the
>> whole transmit path (MAC + PHY).
> 
> Hi Florian
> 
> I read a couple of datasheets for a few phys doing EEE. Both said the
> same, the MAC has to indicate to the PHY when low power should be
> entered and existed. The PHY itself does not appear to do anything on
> its own.

Oh you are right, the LPI signal has to come from the MAC for the PHY to
decide how to do the idle signaling, my bad.

> 
> It would be good to read the standards about this. But i don't think
> we should tell userspace EEE is enabled, if the PHY has it enabled,
> but the MAC is not capable and hence EEE is not actually being used at
> all.
-- 
Florian