OK. The issue is not related to linuxptp v3.1. Thank you for pointing
the clamp.
Is it common for phc2sys and ts2phc also ?
best regards
Janusz
W dniu 06/10/2022 o 09:19, Janusz Użycki pisze:
On Thu, Oct 06, 2022 at 12:11:39AM +0200, Janusz Użycki wrote:
Hi.
A lot of PTP/PHC drivers set max_adj value quite big. Howover due to
kernel's API limit of 32bit long type value (freq) and POSIX frequency
conversion it should limited to 32767999 ppb.
It concerns the frequency limit check both for kernel, testptp and
ptp4linux
servos. Simply 65.536 * 32767999 is almost 2^31... It is also common
for
adjfreq() vs newer adjfine().
Moreover such big frequency limits seem not practical (phase jump used
instead, 1000ppm is huge for any PTP oscillator application), even
driver or
rather PHC hardware has ability to tune is such range.
What issue are you seeing with linuxptp?
In phc_max_adj() there is some code clamping the value on 32-bit
systems, so the overflow should be avoided.
When I set testptp -f 32768000 or more PHC time starts to drift in
opposite direction relative to synced REALTIME system clock, tested
using testptp -k1.
First I noted the issue on much older kernel than latest mainline.
best regrds
Janusz
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