netdev - Re: [PATCH net-next v5 4/4] phy: aquantia: Determine rate adaptation support from registers

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Date:   Thu, 5 Jan 2023 13:59:27 -0500
From:   Sean Anderson <sean.anderson@...o.com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>,
        Vladimir Oltean <olteanv@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>, netdev@...r.kernel.org,
        "David S . Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>, linux-kernel@...r.kernel.org,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Tim Harvey <tharvey@...eworks.com>
Subject: Re: [PATCH net-next v5 4/4] phy: aquantia: Determine rate adaptation
 support from registers

On 1/5/23 13:55, Russell King (Oracle) wrote:
> On Thu, Jan 05, 2023 at 07:52:06PM +0200, Vladimir Oltean wrote:
>> On Thu, Jan 05, 2023 at 12:43:47PM -0500, Sean Anderson wrote:
>> > Again, this is to comply with the existing API assumptions. The current
>> > code is buggy. Of course, another way around this is to modify the API.
>> > I have chosen this route because I don't have a situation like you
>> > described. But if support for that is important to you, I encourage you
>> > to refactor things.
>> 
>> I don't think I'm aware of a practical situation like that either.
>> I remember seeing some S32G boards with Aquantia PHYs which use 2500BASE-X
>> for 2.5G and SGMII for <=1G, but that's about it in terms of protocol switching.
> 
> 88x3310 can dynamically switch between 10GBASE-R, 5GBASE-R, 2500BASE-X
> and SGMII if rate adaption is not being used (and the rate adaption
> method it supports in non-MACSEC PHYs is only via increasing the IPG on
> the MAC... which currently no MAC driver supports.)
> 

As an aside, do you know of any MACs which support open-loop rate
matching to below ~95% of the line rate (the amount necessary for
10GBASE-W)?

--Sean