linux-kernel - Re: [PATCH net-next] net: phy: adin: allow control of Fast Link Down

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Message-ID: <b16f4344-815c-429f-b3b5-58715b32e1db@lunn.ch>
Date:   Tue, 28 Nov 2023 21:23:42 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Vincent Whitchurch <vincent.whitchurch@...s.com>
Cc:     Michael Hennerich <michael.hennerich@...log.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel@...s.com
Subject: Re: [PATCH net-next] net: phy: adin: allow control of Fast Link Down

On Tue, Nov 28, 2023 at 09:18:00PM +0100, Andrew Lunn wrote:
> On Mon, Nov 27, 2023 at 04:31:39PM +0100, Vincent Whitchurch wrote:
> > Add support to allow Fast Link Down (aka "Enhanced link detection") to
> > be controlled via the ETHTOOL_PHY_FAST_LINK_DOWN tunable.  These PHYs
> > have this feature enabled by default.
> > 
> > Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
> 
> Reviewed-by: Andrew Lunn <andrew@...n.ch>
> 
> Is there anything in the datasheet about how fast it is? It would be
> nice to return the number of milliseconds, if its known.

Datasheet says:

 If enhanced link detection is enabled (it is enabled by default), the
 ADIN1300 typically reacts to a break in the cable within 10 μs and
 indicates link down via the LINK_ST pin. If enhanced link detection
 is not enabled, the ADIN1300 follows the IEEE standard, and in
 100BASE-TX, it can take more than either 350 ms or 750 ms in
 1000BASE-T, depending if the PHY is 1000BASE-T master or 1000BASE-T
 slave.

10uS is closer to 0ms and 1ms, so ETHTOOL_PHY_FAST_LINK_DOWN_ON == 0
is right.

   Andrew