netdev - Re: [PATCH net-next 1/3] ethtool: (uapi) Add ETHTOOL_PHY

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Message-ID: <025d5123-147f-346a-223d-b3a51e830cdd@gmail.com>
Date:   Mon, 28 Nov 2016 09:59:11 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Andrew Lunn <andrew@...n.ch>,
        "Allan W. Nielsen" <allan.nielsen@...rosemi.com>
Cc:     netdev@...r.kernel.org, raju.lakkaraju@...rosemi.com
Subject: Re: [PATCH net-next 1/3] ethtool: (uapi) Add ETHTOOL_PHY_LOOPBACK to
 PHY tunables

On 11/28/2016 06:14 AM, Andrew Lunn wrote:
> On Mon, Nov 28, 2016 at 02:24:30PM +0100, Allan W. Nielsen wrote:
>> From: Raju Lakkaraju <Raju.Lakkaraju@...rosemi.com>
>>
>> 3 types of PHY loopback are supported.
>> i.e. Near-End Loopback, Far-End Loopback and External Loopback.
> 
> Hi Allan
> 
> Is this integrated with ethtool --test? You only want the PHY to go
> into loopback mode when running ethtool --test external_lb or maybe
> ethtool --test offline.
> 
> What i think should happen is that this tunable sets the mode the PHY
> will go into when loopback is enabled. It does not however enable
> loopback. It is running ethtool --test which actually enables the
> loopback, probably by setting BMCR_LOOPBACK. Once the test is
> finished, the bit is cleared and the PHY goes back into normal
> operation.

Agreed with Andrew, there needs to be a tight coupling between the
existing ethtool test infrastructure, and how to perform PHY loopback
testing.

It makes sense for the PHY drivers to be able to implement specific
loopback/test mode, but we need to clarify how these get called from
ethtool --test for instance, and if the Ethernet MAC driver needs to do
something specific as well.
-- 
Florian