diff options
| -rw-r--r-- | Documentation/driver-api/ptp.rst | 16 | ||||
| -rw-r--r-- | include/linux/ptp_clock_kernel.h | 6 |
2 files changed, 20 insertions, 2 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 ================== diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h index fdffa6a98d79..f8e8443a8b35 100644 --- a/include/linux/ptp_clock_kernel.h +++ b/include/linux/ptp_clock_kernel.h @@ -77,8 +77,10 @@ struct ptp_system_timestamp { * nominal frequency in parts per million, but with a * 16 bit binary fractional field. * - * @adjphase: Adjusts the phase offset of the hardware clock. - * parameter delta: Desired change in nanoseconds. + * @adjphase: Indicates that the PHC should use an internal servo + * algorithm to correct the provided phase offset. + * parameter delta: PHC servo phase adjustment target + * in nanoseconds. * * @adjtime: Shifts the time of the hardware clock. * parameter delta: Desired change in nanoseconds. |