From a05d070a6164bd0578991e42181a52b9c7cf630c Mon Sep 17 00:00:00 2001 From: Rahul Rameshbabu Date: Mon, 12 Jun 2023 14:14:52 -0700 Subject: 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 Cc: Richard Cochran Signed-off-by: Rahul Rameshbabu Acked-by: Richard Cochran Signed-off-by: David S. Miller --- Documentation/driver-api/ptp.rst | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'Documentation/driver-api') 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 ================== -- cgit v1.2.3