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
