From: Michael Walle <michael@walle.cc>
To: Andrew Lunn <andrew@lunn.ch>
Cc: Florian Fainelli <f.fainelli@gmail.com>,
cphealy@gmail.com, davem@davemloft.net, hkallweit1@gmail.com,
mkubecek@suse.cz, netdev@vger.kernel.org
Subject: Re: [PATCH net-next v1 0/9] Ethernet Cable test support
Date: Thu, 30 Apr 2020 22:01:55 +0200 [thread overview]
Message-ID: <4cae330197a5bdd1559dcea3482f0732@walle.cc> (raw)
In-Reply-To: <20200430194143.GF107658@lunn.ch>
Am 2020-04-30 21:41, schrieb Andrew Lunn:
>> ECD. The registers looks exactly like the one from the Marvell PHYs,
>> which makes me wonder if both have the same building block or if one
>> imitated the registers of the other. There are subtle differences
>> like one bit in the broadcom PHY is "break link" and is self-clearing,
>> while the bit on the Marvell PHY is described as "perform diagnostics
>> on link break".
>
> Should we be sharing code between the two drivers?
If they are indeed the same sure, but it doesn't look like that the
marvell procedure works for the broadcom PHY.
>> What do you mean by calibrate it?
>
> Some of the Marvell documentation talks about calibrating for losses
> on the PCB. Run a diagnostics with no cable plugged in, and get the
> cable length to the 'fault'. This gives you the distance to the RJ45
> socket. You should then subtract that from all subsequent results.
> But since this is board design specific, i decided to ignore it. I
> suppose it could be stuffed into a DT property, but i got the feeling
> it is not worth it, given the measurement granularity of 80cm.
Oh so, the time delta counter of the Marvell PHY also runs at 125MHz? ;)
/* Accoring to the datasheet the distance to the fault is
* DELTA_TIME * 0.824 meters.
*
* The author suspect the correct formula is:
* distance in meters = (c * VF) / (2 * 125MHz)
* where c is the speed of light, VF is the velocity factor of
* the twisted pair cable, 125MHz the counter frequency and
* the factor 2 because the hardware will measure the round
* trip time.
* With a VF of 0.69 we get the factor 0.824 mentioned in the
* datasheet.
*/
-michael
next prev parent reply other threads:[~2020-04-30 20:01 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-25 18:06 [PATCH net-next v1 0/9] Ethernet Cable test support Andrew Lunn
2020-04-25 18:06 ` [PATCH net-next v1 1/9] net: phy: Add cable test support to state machine Andrew Lunn
2020-04-26 19:46 ` Michal Kubecek
2020-04-26 20:31 ` Andrew Lunn
2020-04-26 21:22 ` Florian Fainelli
2020-04-25 18:06 ` [PATCH net-next v1 2/9] net: phy: Add support for polling cable test Andrew Lunn
2020-04-25 19:49 ` Florian Fainelli
2020-04-25 20:10 ` Andrew Lunn
2020-04-26 21:19 ` Florian Fainelli
2020-04-26 22:07 ` Andrew Lunn
2020-04-25 18:06 ` [PATCH net-next v1 3/9] net: ethtool: netlink: Add support for triggering a " Andrew Lunn
2020-04-26 19:36 ` Michal Kubecek
2020-04-26 20:38 ` Andrew Lunn
2020-04-26 20:50 ` Michal Kubecek
2020-04-25 18:06 ` [PATCH net-next v1 4/9] net: ethtool: Add attributes for cable test reports Andrew Lunn
2020-04-25 20:00 ` Randy Dunlap
2020-04-26 20:25 ` Michal Kubecek
2020-04-26 21:12 ` Andrew Lunn
2020-04-27 7:13 ` Michal Kubecek
2020-04-29 16:16 ` Michael Walle
2020-04-29 18:57 ` Andrew Lunn
2020-04-29 18:58 ` Florian Fainelli
2020-04-29 19:32 ` Michael Walle
2020-04-25 18:06 ` [PATCH net-next v1 5/9] net: ethtool: Make helpers public Andrew Lunn
2020-04-25 18:06 ` [PATCH net-next v1 6/9] net: ethtool: Add infrastructure for reporting cable test results Andrew Lunn
2020-04-25 18:06 ` [PATCH net-next v1 7/9] net: ethtool: Add helpers for reporting " Andrew Lunn
2020-04-25 18:06 ` [PATCH net-next v1 8/9] net: phy: marvell: Add cable test support Andrew Lunn
2020-04-25 18:06 ` [PATCH net-next v1 9/9] net: phy: Put interface into oper testing during cable test Andrew Lunn
2020-04-29 16:02 ` [PATCH net-next v1 0/9] Ethernet Cable test support Michael Walle
2020-04-29 16:32 ` Andrew Lunn
2020-04-30 17:48 ` Michael Walle
2020-04-30 18:23 ` Andrew Lunn
2020-04-30 19:44 ` Michael Walle
2020-04-30 20:51 ` Andrew Lunn
2020-04-30 18:34 ` Florian Fainelli
2020-04-30 19:31 ` Michael Walle
2020-04-30 19:38 ` Florian Fainelli
2020-04-30 19:52 ` Michael Walle
2020-04-30 19:41 ` Andrew Lunn
2020-04-30 20:01 ` Michael Walle [this message]
2020-04-30 20:56 ` Andrew Lunn
2020-04-30 20:04 ` Florian Fainelli
2020-04-30 20:13 ` Michael Walle
2020-04-30 20:19 ` Florian Fainelli
2020-04-30 21:16 ` Michael Walle
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