linux-kernel - Re: [PATCH net-next v3] net: phy: at803x: add cable diagnostics support

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Date:   Wed, 13 May 2020 13:45:29 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Michael Walle <michael@...le.cc>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S . Miller" <davem@...emloft.net>,
        Oleksij Rempel <o.rempel@...gutronix.de>
Subject: Re: [PATCH net-next v3] net: phy: at803x: add cable diagnostics
 support



On 5/13/2020 1:38 PM, Michael Walle wrote:
> The AR8031/AR8033 and the AR8035 support cable diagnostics. Adding
> driver support is straightforward, so lets add it.
> 
> The PHY just do one pair at a time, so we have to start the test four
> times. The cable_test_get_status() can block and therefore we can just
> busy poll the test completion and continue with the next pair until we
> are done.
> The time delta counter seems to run at 125MHz which just gives us a
> resolution of about 82.4cm per tick.
> 
> 100m cable, A/B/C/D open:
>   Cable test started for device eth0.
>   Cable test completed for device eth0.
>   Pair: Pair A, result: Open Circuit
>   Pair: Pair A, fault length: 107.94m
>   Pair: Pair B, result: Open Circuit
>   Pair: Pair B, fault length: 104.64m
>   Pair: Pair C, result: Open Circuit
>   Pair: Pair C, fault length: 105.47m
>   Pair: Pair D, result: Open Circuit
>   Pair: Pair D, fault length: 107.94m
> 
> 1m cable, A/B connected, C shorted, D open:
>   Cable test started for device eth0.
>   Cable test completed for device eth0.
>   Pair: Pair A, result: OK
>   Pair: Pair B, result: OK
>   Pair: Pair C, result: Short within Pair
>   Pair: Pair C, fault length: 0.82m
>   Pair: Pair D, result: Open Circuit
>   Pair: Pair D, fault length: 0.82m
> 
> Signed-off-by: Michael Walle <michael@...le.cc>
> Reviewed-by: Andrew Lunn <andrew@...n.ch>

Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
-- 
Florian