On 4/30/20 12:31 PM, Michael Walle wrote: > Hi Florian, > > Am 2020-04-30 20:34, schrieb Florian Fainelli: >> On 4/30/20 10:48 AM, Michael Walle wrote: >>> Hi Andrew, >>> >>> Am 2020-04-29 18:32, schrieb Andrew Lunn: >>>> On Wed, Apr 29, 2020 at 06:02:13PM +0200, Michael Walle wrote: >>>>> Hi Andrew, >>>>> >>>>> > Add infrastructure in ethtool and phylib support for triggering a >>>>> > cable test and reporting the results. The Marvell 1G PHY driver is >>>>> > then extended to make use of this infrastructure. >>>>> >>>>> I'm currently trying this with the AR8031 PHY. With this PHY, you >>>>> have to select the pair which you want to start the test on. So >>>>> you'd have to start the test four times in a row for a normal >>>>> gigabit cable. Right now, I don't see a way how to do that >>>>> efficiently if there is no interrupt. One could start another test >>>>> in the get_status() polling if the former was completed >>>>> successfully. But then you'd have to wait at least four polling >>>>> intervals to get the final result (given a cable with four pairs). >>>>> >>>>> Any other ideas? >>>> >>>> Hi Michael >>>> >>>> Nice to see some more PHYs getting support for this. >>>> >>>> It is important that the start function returns quickly. However, the >>>> get status function can block. So you could do all the work in the >>>> first call to get status, polling for completion at a faster rate, >>>> etc. >>> >>> Ok. I do have one problem. TDR works fine for the AR8031 and the >>> BCM54140 as long as there is no link partner, i.e. open cable, >>> shorted pairs etc. But as soon as there is a link partner and a >>> link, both PHYs return garbage. As far as I understand TDR, there >>> must not be a link, correct? The link partner may send data or >>> link pulses. No how do you silence the local NIC or even the peer? >> >> Michael do you use the enhanced cable diagnostics (ECD) or the simple >> cable diagnostics? > > 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". > > I don't know what simple cable diagnostics should be, I guess the > BCM54140 doesn't support it or its not documented. Actually, ECD > has very little documentation in general.
Yes, there is very little information, even internally. My understanding is that diagnostics at run at auto-neg, so you need to break the link, and when the link comes back up is when you should have per-pair results. There are also some caveats, like the link parnter must also have auto-negotiation on for the diagnostics to work. > >> Having tried to get older Broadcom PHYs to work with >> cable diagnostics, you need to calibrate the PHY prior to running >> diagnostics and you need to soft reset it. > > What do you mean by calibrate it? You need to tune the AFE and DSP of the PHY in order for it to report accurate cable lengths. I would not think that you have access to that, and what I got access to is not really well documented, which is why I have not had a chance to submit those changes yet. How accurate are your results when there is no link? -- Florian
