From: Florian Fainelli <f.fainelli@gmail.com>
To: Michael Walle <michael@walle.cc>
Cc: Andrew Lunn <andrew@lunn.ch>,
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 13:19:10 -0700 [thread overview]
Message-ID: <c52e7043-cbd5-8fa0-96e6-e29e783d3a5f@gmail.com> (raw)
In-Reply-To: <b63498f01e64c55124c2c710fffb1047@walle.cc>
On 4/30/20 1:13 PM, Michael Walle wrote:
> Am 2020-04-30 22:04, schrieb Florian Fainelli:
>> On 4/30/20 12:41 PM, Andrew Lunn wrote:
>>>> 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?
>>
>> Yes, I am amazed how how identical they are, nearly on a bit level
>> identical, the coincidence is uncanny. The expansion registers are also
>> 0x10 - 0x15 just in the reverse order,
>
> At what PHY are you looking? I've just found some datasheets where they
> are at 0xC0 to 0xC5.
BCM54810 because that's what I have on my desk right now, but 0x10 would
be the offset relative to the expansion register space, which would
translate into this:
https://github.com/ffainelli/linux/commits/broadcom-cable-tests
(sorry for the mess it is a patchwork of tests on various platforms,
based on an earlier branch from Andrew).
>
>> you know, so as to make it not
>> too obvious this looks about the same ;) I wonder if we managed to find
>> something here.
>>
>>>
>>>> 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.
>>
>> OK, accuracy is different here, they are said to be +/- 5m accurate for
>> cable faults and +/- 10m accurate for good cables.
>
> Accuracy != granularity. But yes, if one digit correspond to 80cm it
> doesn't really make sense to remove the PCB trace error if you assume
> that it might add just one digit at most.
One of the test racks that I use has very short cables, but I guess it
does not matter if they get reported as 80cm or 160cm...
--
Florian
next prev parent reply other threads:[~2020-04-30 20:19 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
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 [this message]
2020-04-30 21:16 ` Michael Walle
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