netdev - Re: [RFC] net: dsa: slave: Advertise correct EEE capabilities at slave PHY setup

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Message-ID: <20230530164731.0b711649@wsk>
Date: Tue, 30 May 2023 16:47:31 +0200
From: Lukasz Majewski <lukma@...x.de>
To: Andrew Lunn <andrew@...n.ch>
Cc: "Russell King (Oracle)" <linux@...linux.org.uk>, Vivien Didelot
 <vivien.didelot@...il.com>, Florian Fainelli <f.fainelli@...il.com>,
 Vladimir Oltean <olteanv@...il.com>, "David S. Miller"
 <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] net: dsa: slave: Advertise correct EEE capabilities at
 slave PHY setup

Hi Andrew,

> > So, I'm wondering what's actually going on here... can you give
> > any more details about the hardware setup?  
> 
> And what switch it actually is.

It is mv88e6071.

> I've not looked in too much detail,
> but i think different switch families have different EEE capabilities.

Yes, some (like b53) have the ability to disable EEE in the HW.

The above one from Marvell seems to have EEE always enabled (in silicon)
and the only possibility is to not advertise it [*].

> But in general, as Russell pointed out, there is no MAC support for
> EEE in the mv88e6xxx driver.

I may be wrong, but aren't we accessing this switch PHYs via c45 ?
(MDIO_MMD_PCS devices and e.g. MDIO_PCS_EEE_ABLE registers)?

> 
>     Andrew

[*] - maybe it is possible via some "reserved" registers. However,
there are "register pages" for EEE, which allow tuning timers.

Best regards,

Lukasz Majewski

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