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Diffstat (limited to 'Documentation/driver-api/dpll.rst')
| -rw-r--r-- | Documentation/driver-api/dpll.rst | 97 |
1 files changed, 80 insertions, 17 deletions
diff --git a/Documentation/driver-api/dpll.rst b/Documentation/driver-api/dpll.rst index e6855cd37e85..83118c728ed9 100644 --- a/Documentation/driver-api/dpll.rst +++ b/Documentation/driver-api/dpll.rst @@ -179,29 +179,47 @@ 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 -handle shall be provide to the user on ``DPLL_CMD_PIN_GET`` respond -with ``DPLL_A_PIN_PHASE_ADJUST_MIN`` and ``DPLL_A_PIN_PHASE_ADJUST_MAX`` +If pin phase adjustment is supported, minimal and maximal values and +granularity that pin handle shall be provided to the user on +``DPLL_CMD_PIN_GET`` respond with ``DPLL_A_PIN_PHASE_ADJUST_MIN``, +``DPLL_A_PIN_PHASE_ADJUST_MAX`` and ``DPLL_A_PIN_PHASE_ADJUST_GRAN`` attributes. Configured phase adjust value is provided with ``DPLL_A_PIN_PHASE_ADJUST`` attribute of a pin, and value change can be requested with the same attribute with ``DPLL_CMD_PIN_SET`` command. - =============================== ====================================== - ``DPLL_A_PIN_ID`` configured pin id - ``DPLL_A_PIN_PHASE_ADJUST_MIN`` attr minimum value of phase adjustment - ``DPLL_A_PIN_PHASE_ADJUST_MAX`` attr maximum value of phase adjustment - ``DPLL_A_PIN_PHASE_ADJUST`` attr configured value of phase - adjustment on parent dpll device - ``DPLL_A_PIN_PARENT_DEVICE`` nested attribute for requesting - configuration on given parent dpll - device - ``DPLL_A_PIN_PARENT_ID`` parent dpll device id - ``DPLL_A_PIN_PHASE_OFFSET`` attr measured phase difference - between a pin and parent dpll device - =============================== ====================================== + ================================ ========================================== + ``DPLL_A_PIN_ID`` configured pin id + ``DPLL_A_PIN_PHASE_ADJUST_GRAN`` attr granularity of phase adjustment value + ``DPLL_A_PIN_PHASE_ADJUST_MIN`` attr minimum value of phase adjustment + ``DPLL_A_PIN_PHASE_ADJUST_MAX`` attr maximum value of phase adjustment + ``DPLL_A_PIN_PHASE_ADJUST`` attr configured value of phase + adjustment on parent dpll device + ``DPLL_A_PIN_PARENT_DEVICE`` nested attribute for requesting + configuration on given parent dpll + device + ``DPLL_A_PIN_PARENT_ID`` parent dpll device id + ``DPLL_A_PIN_PHASE_OFFSET`` attr measured phase difference + between a pin and parent dpll device + ================================ ========================================== All phase related values are provided in pico seconds, which represents time difference between signals phase. The negative value means that @@ -214,6 +232,24 @@ offset values are fractional with 3-digit decimal places and shell be divided with ``DPLL_PIN_PHASE_OFFSET_DIVIDER`` to get integer part and modulo divided to get fractional part. +Phase offset monitor +==================== + +Phase offset measurement is typically performed against the current active +source. However, some DPLL (Digital Phase-Locked Loop) devices may offer +the capability to monitor phase offsets across all available inputs. +The attribute and current feature state shall be included in the response +message of the ``DPLL_CMD_DEVICE_GET`` command for supported DPLL devices. +In such cases, users can also control the feature using the +``DPLL_CMD_DEVICE_SET`` command by setting the ``enum dpll_feature_state`` +values for the attribute. +Once enabled the phase offset measurements for the input shall be returned +in the ``DPLL_A_PIN_PHASE_OFFSET`` attribute. + + =============================== ======================== + ``DPLL_A_PHASE_OFFSET_MONITOR`` attr state of a feature + =============================== ======================== + Embedded SYNC ============= @@ -235,6 +271,31 @@ the pin. ``DPLL_A_PIN_ESYNC_PULSE`` pulse type of Embedded SYNC ========================================= ================================= +Reference SYNC +============== + +The device may support the Reference SYNC feature, which allows the combination +of two inputs into a input pair. In this configuration, clock signals +from both inputs are used to synchronize the DPLL device. The higher frequency +signal is utilized for the loop bandwidth of the DPLL, while the lower frequency +signal is used to syntonize the output signal of the DPLL device. This feature +enables the provision of a high-quality loop bandwidth signal from an external +source. + +A capable input provides a list of inputs that can be bound with to create +Reference SYNC. To control this feature, the user must request a desired +state for a target pin: use ``DPLL_PIN_STATE_CONNECTED`` to enable or +``DPLL_PIN_STATE_DISCONNECTED`` to disable the feature. An input pin can be +bound to only one other pin at any given time. + + ============================== ========================================== + ``DPLL_A_PIN_REFERENCE_SYNC`` nested attribute for providing info or + requesting configuration of the Reference + SYNC feature + ``DPLL_A_PIN_ID`` target pin id for Reference SYNC feature + ``DPLL_A_PIN_STATE`` state of Reference SYNC connection + ============================== ========================================== + Configuration commands group ============================ @@ -325,6 +386,8 @@ according to attribute purpose. frequencies ``DPLL_A_PIN_ANY_FREQUENCY_MIN`` attr minimum value of frequency ``DPLL_A_PIN_ANY_FREQUENCY_MAX`` attr maximum value of frequency + ``DPLL_A_PIN_PHASE_ADJUST_GRAN`` attr granularity of phase + adjustment value ``DPLL_A_PIN_PHASE_ADJUST_MIN`` attr minimum value of phase adjustment ``DPLL_A_PIN_PHASE_ADJUST_MAX`` attr maximum value of phase |