diff options
Diffstat (limited to 'Documentation/driver-api/dpll.rst')
| -rw-r--r-- | Documentation/driver-api/dpll.rst | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/Documentation/driver-api/dpll.rst b/Documentation/driver-api/dpll.rst index eca72d9b9ed8..be1fc643b645 100644 --- a/Documentation/driver-api/dpll.rst +++ b/Documentation/driver-api/dpll.rst @@ -179,7 +179,23 @@ Phase offset measurement and adjustment Device may provide ability to measure a phase difference between signals on a pin and its parent dpll device. If pin-dpll phase offset measurement is supported, it shall be provided with ``DPLL_A_PIN_PHASE_OFFSET`` -attribute for each parent dpll device. +attribute for each parent dpll device. The reported phase offset may be +computed as the average of prior values and the current measurement, using +the following formula: + +.. math:: + curr\_avg = prev\_avg * \frac{2^N-1}{2^N} + new\_val * \frac{1}{2^N} + +where `curr_avg` is the current reported phase offset, `prev_avg` is the +previously reported value, `new_val` is the current measurement, and `N` is +the averaging factor. Configured averaging factor value is provided with +``DPLL_A_PHASE_OFFSET_AVG_FACTOR`` attribute of a device and value change can +be requested with the same attribute with ``DPLL_CMD_DEVICE_SET`` command. + + ================================== ====================================== + ``DPLL_A_PHASE_OFFSET_AVG_FACTOR`` attr configured value of phase offset + averaging factor + ================================== ====================================== Device may also provide ability to adjust a signal phase on a pin. If pin phase adjustment is supported, minimal and maximal values that pin |