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

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Message-ID: <20230530154039.4552e08a@wsk>
Date: Tue, 30 May 2023 15:40:39 +0200
From: Lukasz Majewski <lukma@...x.de>
To: Andrew Lunn <andrew@...n.ch>
Cc: Russell King <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,

> On Tue, May 30, 2023 at 02:26:21PM +0200, Lukasz Majewski wrote:
> > One can disable in device tree advertising of EEE capabilities of
> > PHY when 'eee-broken-100tx' property is present in DTS.
> > 
> > With DSA switch it also may happen that one would need to disable
> > EEE due to some network issues.  
> 
> Is EEE actually broken in the MAC/PHY combination?
> 

Problem is that when I connect on this project some non-manageable
switches (which by default have EEE enabled), then I observe very rare
and sporadic link loss and reconnection.

Disabling EEE solves the problem.

> You should not be using this DT option for configuration. It is there
> because there is some hardware which is truly broken, and needs EEE
> turned off.

Yes, I do think that the above sentence sums up my use case.

> 
> If EEE does work, but you need to turn it off because of latency etc,
> then please use ethtool.
> 

Yes, correct - it is possible to disable the EEE with 

ethtool --set-eee lan2 eee off

However, as I've stated in the mail, I cannot re-enable EEE once
disabled with:

ethtool --set-eee lan2 eee on

ethtool --show-eee lan2
EEE Settings for lan2:
        EEE status: not supported

As the capability register shows value of 0.

>      Andrew,

Best regards,

Lukasz Majewski

--

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Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@...x.de

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