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author | Rahul Rameshbabu <rrameshbabu@nvidia.com> | 2023-06-12 23:14:52 +0200 |
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committer | David S. Miller <davem@davemloft.net> | 2023-06-20 10:02:32 +0200 |
commit | a05d070a6164bd0578991e42181a52b9c7cf630c (patch) | |
tree | c3e112933bbe87f5531c390b6555595715bcc37e /Documentation/driver-api | |
parent | Merge branch 'ipv6-random-cleanup-for-extension-header' (diff) | |
download | linux-a05d070a6164bd0578991e42181a52b9c7cf630c.tar.xz linux-a05d070a6164bd0578991e42181a52b9c7cf630c.zip |
ptp: Clarify ptp_clock_info .adjphase expects an internal servo to be used
.adjphase expects a PHC to use an internal servo algorithm to correct the
provided phase offset target in the callback. Implementation of the
internal servo algorithm are defined by the individual devices.
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Rahul Rameshbabu <rrameshbabu@nvidia.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'Documentation/driver-api')
-rw-r--r-- | Documentation/driver-api/ptp.rst | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/Documentation/driver-api/ptp.rst b/Documentation/driver-api/ptp.rst index 664838ae7776..4552a1f20488 100644 --- a/Documentation/driver-api/ptp.rst +++ b/Documentation/driver-api/ptp.rst @@ -73,6 +73,22 @@ Writing clock drivers class driver, since the lock may also be needed by the clock driver's interrupt service routine. +PTP hardware clock requirements for '.adjphase' +----------------------------------------------- + + The 'struct ptp_clock_info' interface has a '.adjphase' function. + This function has a set of requirements from the PHC in order to be + implemented. + + * The PHC implements a servo algorithm internally that is used to + correct the offset passed in the '.adjphase' call. + * When other PTP adjustment functions are called, the PHC servo + algorithm is disabled. + + **NOTE:** '.adjphase' is not a simple time adjustment functionality + that 'jumps' the PHC clock time based on the provided offset. It + should correct the offset provided using an internal algorithm. + Supported hardware ================== |