Hello,
When I use linuxptp with phc2sys or ptp4l, after an variable amount of time,
I've got an offset explosion. I use an Intel 82574l chip.
I investigated in the code and I found out that the problem comes from the
readout of the SYSTIMH register (ine1000e_cyclecounter_read function).
The value read in this register should always increase (or at least be equal to
the last value read). But sometimes, the value read is smaller that the last
one !
Here are three examples :
ex 1 :
er32(SYSTIMH) -> 0x00D3842C er32(SYSTIML)->0x0C600000
er32(SYSTIMH) -> 0x00D3842D er32(SYSTIML)->0x79600000
er32(SYSTIMH) -> 0x00D3842E er32(SYSTIML)->0x54200000
er32(SYSTIMH) -> 0x00D3842F er32(SYSTIML)->0x29E00000
er32(SYSTIMH) -> 0x00D38420 er32(SYSTIML)->0xFFA00000 Problem !
er32(SYSTIMH) -> 0x00D39326 er32(SYSTIML)->0x16C00000
er32(SYSTIMH) -> 0x00D39327 er32(SYSTIML)->0x5EE00000
er32(SYSTIMH) -> 0x00D39328 er32(SYSTIML)->0x3AE00000
er32(SYSTIMH) -> 0x00D39329 er32(SYSTIML)->0x10000000
er32(SYSTIMH) -> 0x00D39329 er32(SYSTIML)->0xE4800000
ex 2 :
er32(SYSTIMH) -> 0x0799808E er32(SYSTIML)->0x07A00000
er32(SYSTIMH) -> 0x0799808D er32(SYSTIML)->0x7A400000
er32(SYSTIMH) -> 0x0799808C er32(SYSTIML)->0x55A00000
er32(SYSTIMH) -> 0x0799808F er32(SYSTIML)->0x2AC00000
er32(SYSTIMH) -> 0x07998089 er32(SYSTIML)->0xFFE00000 Problem !
er32(SYSTIMH) -> 0x07998F86 er32(SYSTIML)->0x1DE00000
er32(SYSTIMH) -> 0x07998F87 er32(SYSTIML)->0x6F600000
er32(SYSTIMH) -> 0x07998F88 er32(SYSTIML)->0x4DE00000
er32(SYSTIMH) -> 0x07998F89 er32(SYSTIML)->0x23A00000
er32(SYSTIMH) -> 0x07998F89 er32(SYSTIML)->0xF8C00000
ex 3 :
er32(SYSTIMH) -> 0x0D8854EB er32(SYSTIML)->0x4A800000
er32(SYSTIMH) -> 0x0D8863E1 er32(SYSTIML)->0xD5E00000
er32(SYSTIMH) -> 0x0D8863E3 er32(SYSTIML)->0x23A00000
er32(SYSTIMH) -> 0x0D8863E1 er32(SYSTIML)->0xFFA00000 Problem !
er32(SYSTIMH) -> 0x0D8863E4 er32(SYSTIML)->0xD6000000
er32(SYSTIMH) -> 0x0D8863E5 er32(SYSTIML)->0xA9400000
er32(SYSTIMH) -> 0x0D8872DD er32(SYSTIML)->0x8F800000
Does someone know what could be the origin of that ?
It seems that it only affects the 4 first bits of the register. The value read
after the iteration when the problem occurs seems to be good (regarding to the
value before the bad iteration) if I consider the average interval between two
readings (five consecutive readings). So, the problem doesn't seem to come from
the counter but the reading of it.
By the way, I've got an other problem with phc2sys which could come from the
driver or the ethernet chip :
The offset between the phc and CLOCK_REALTIME can be good (less than a 100 ns)
but a few days after, without any identified reason, it can be very bad
(several microseconds) et be good again after a while. All that with the same
hardware, software and similar environmental conditions ! Any idea ?
Thank you,
Julien.
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