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Date: Sat, 25 Jul 2020 13:49:27 +0100 From: Russell King - ARM Linux admin <linux@...linux.org.uk> To: Richard Cochran <richardcochran@...il.com> Cc: netdev@...r.kernel.org Subject: phc2sys - does it work? Hi, I've been writing another PTP clock driver, and I'm wondering whether phc2sys is actually working correctly. I'm running it with: phc2sys -c /dev/ptp1 -s CLOCK_REALTIME -q -m -O 0 and I have additional pr_info() to debug in the clock driver. What I see is the "sys offset" that phc2sys comes out with doesn't seem to make much sense: kt: 000000005f1c273ds 371ce3f5ns t: 00005f1c273ds 374c6cf5.2ae8ac76ns kt: 000000005f1c273ds 377bf04cns t: 00005f1c273ds 37ab792b.4ef91e82ns kt: 000000005f1c273ds 37daf7ccns t: 00005f1c273ds 380a80c3.5d12653ans kt: 000000005f1c273ds 383a143cns t: 00005f1c273ds 38699d5c.cf1319f2ns kt: 000000005f1c273ds 38992094ns t: 00005f1c273ds 38c8a9c8.f4247162ns kt: 000000005f1c273ds 38f82d13ns t: 00005f1c273ds 3927b640.196edf5ans kt: 000000005f1c273ds 3957323bns t: 00005f1c273ds 3986bb74.1c28a8fans kt: 000000005f1c273ds 39b643e3ns t: 00005f1c273ds 39e5cd56.5b34c14ens kt: 000000005f1c273ds 3a155d5ans t: 00005f1c273ds 3a44e6bf.be0b79e6ns kt: 000000005f1c273ds 3a746fcans t: 00005f1c273ds 3aa3f943.001a4266ns phc2sys[127.224]: /dev/ptp1 sys offset 5788 s2 freq -69793 delay 6229046 Here, ktime_real (kt) is behind the ptp timestamp (t), and we have a positive "sys offset". This continues for a while: kt: 000000005f1c2743s 0e1c25bdns t: 00005f1c2743s 0e4ba86d.91ebf06ans kt: 000000005f1c2743s 0e7b3801ns t: 00005f1c2743s 0eaaba44.601c1f30ns kt: 000000005f1c2743s 0eda4225ns t: 00005f1c2743s 0f09c4c3.0fa0d134ns kt: 000000005f1c2743s 0f395a82ns t: 00005f1c2743s 0f68dd0a.f8abbf48ns kt: 000000005f1c2743s 0f986abens t: 00005f1c2743s 0fc7ed41.c00f543cns kt: 000000005f1c2743s 0ff773cans t: 00005f1c2743s 1026f675.6a32920cns kt: 000000005f1c2743s 1056784ens t: 00005f1c2743s 1085fad9.003b24aans kt: 000000005f1c2743s 10b57fcans t: 00005f1c2743s 10e50267.a378bd3cns kt: 000000005f1c2743s 111481f6ns t: 00005f1c2743s 1144047b.2fde6accns kt: 000000005f1c2743s 117387b9ns t: 00005f1c2743s 11a30a5c.cc1d52b4ns phc2sys[132.536]: /dev/ptp1 sys offset 4882 s2 freq -62617 delay 6227425 kt is still behind t, and we still have a positive "sys offset". kt: 000000005f1c2744s 11d56067ns t: 00005f1c2744s 120473bd.c6a08dbfns kt: 000000005f1c2744s 12346f54ns t: 00005f1c2744s 1263806f.d008fce3ns kt: 000000005f1c2744s 12937d7ans t: 00005f1c2744s 12c28c2b.d57fe555ns kt: 000000005f1c2744s 12f29f00ns t: 00005f1c2744s 1321ab52.2aa69e70ns kt: 000000005f1c2744s 1351aedens t: 00005f1c2744s 1380b903.38258359ns kt: 000000005f1c2744s 13b0c614ns t: 00005f1c2744s 13dfcdef.635079dbns kt: 000000005f1c2744s 140fd641ns t: 00005f1c2744s 143edba0.70cf5ec4ns kt: 000000005f1c2744s 146ee8c7ns t: 00005f1c2744s 149debf2.8913fe8dns kt: 000000005f1c2744s 14cdf64dns t: 00005f1c2744s 14fcf6d6.8b147d37ns kt: 000000005f1c2744s 152d1233ns t: 00005f1c2744s 155c10cf.caf99eb8ns phc2sys[133.599]: /dev/ptp1 sys offset -25014 s2 freq -91049 delay 6229170 kt is still behind t, but now we have a negative "sys offset" ? kt: 000000005f1c2745s 158f0f04ns t: 00005f1c2745s 15bd0ce3.e88dec93ns kt: 000000005f1c2745s 15ee1e79ns t: 00005f1c2745s 161c1aa9.0c161488ns kt: 000000005f1c2745s 16503ebcns t: 00005f1c2745s 167e3973.7b6c4843ns kt: 000000005f1c2745s 16b0ebb1ns t: 00005f1c2745s 16dee4f2.436c858dns kt: 000000005f1c2745s 1711806dns t: 00005f1c2745s 173f7822.7a65ccddns kt: 000000005f1c2745s 177215f1ns t: 00005f1c2745s 17a00c04.b57f3ef8ns kt: 000000005f1c2745s 17d15448ns t: 00005f1c2745s 17ff48bd.f1275cb3ns kt: 000000005f1c2745s 1830735dns t: 00005f1c2745s 185e6670.73b72a47ns kt: 000000005f1c2745s 188f95bbns t: 00005f1c2745s 18bd8724.082da8dbns kt: 000000005f1c2745s 18ee9e77ns t: 00005f1c2745s 191c8e4e.044592dcns phc2sys[134.662]: /dev/ptp1 sys offset -98237 s2 freq -171776 delay 6227754 ... and an even bigger negative "sys offset" but kt is still behind t. kt: 000000005f1c2746s 16ad1681ns t: 00005f1c2746s 16db503d.5a2783d6ns kt: 000000005f1c2746s 170f8b80ns t: 00005f1c2746s 173dc5a6.91660baans kt: 000000005f1c2746s 176ed88fns t: 00005f1c2746s 179d1366.45f7dc3ans kt: 000000005f1c2746s 17cdebcdns t: 00005f1c2746s 17fc2725.6da454bbns kt: 000000005f1c2746s 182cfb23ns t: 00005f1c2746s 185b371b.6ab43403ns kt: 000000005f1c2746s 188c0208ns t: 00005f1c2746s 18ba3e8f.07fd0ee9ns kt: 000000005f1c2746s 18eb07fdns t: 00005f1c2746s 1919451f.9b3f2f2bns kt: 000000005f1c2746s 194a13e3ns t: 00005f1c2746s 19785178.6fad0c97ns kt: 000000005f1c2746s 19a915c8ns t: 00005f1c2746s 19d753fa.d549cdabns phc2sys[135.674]: /dev/ptp1 sys offset -77622 s2 freq -180632 delay 6226562 ... same story. I added the debug (which dramatically increased delay) because I notice that phc2sys exhibits random sudden jumps in the "sys offset" value. I've noticed it with this driver (which, without the debug, reports a delay of around 5000) and also with the Marvell PHY PTP driver. I had put the Marvell PHY PTP driver instability down to other MDIO bus activity, as the delay would increase, but that is not the case here. There _is_ something odd going on with the adjfine adjustment, but I can't fathom that (which is another reason for adding the above debug.) If I undo some of the debug, this is the kind of thing I see: phc2sys[20.697]: /dev/ptp1 sys offset 2 s2 freq -25586 delay 5244 phc2sys[21.698]: /dev/ptp1 sys offset 17 s2 freq -25570 delay 5262 phc2sys[22.698]: /dev/ptp1 sys offset -11 s2 freq -25593 delay 5250 phc2sys[23.698]: /dev/ptp1 sys offset -14 s2 freq -25600 delay 5265 phc2sys[24.698]: /dev/ptp1 sys offset -17 s2 freq -25607 delay 5250 phc2sys[25.698]: /dev/ptp1 sys offset 64 s2 freq -25531 delay 5244 phc2sys[26.698]: /dev/ptp1 sys offset -9 s2 freq -25585 delay 5251 phc2sys[27.699]: /dev/ptp1 sys offset -44 s2 freq -25622 delay 5250 phc2sys[28.699]: /dev/ptp1 sys offset 35 s2 freq -25557 delay 5262 phc2sys[29.699]: /dev/ptp1 sys offset -433522 s2 freq -459103 delay 5256 phc2sys[30.699]: /dev/ptp1 sys offset -500029 s2 freq -655667 delay 5228 phc2sys[31.700]: /dev/ptp1 sys offset -369958 s2 freq -675604 delay 5259 Notice the sudden massive jump in sys offset. Any ideas? -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
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