docs/devel/clocks.rst

56 The state of a clock is its period; it is stored as an integer
63 the current period of a clock to be fetched at any time. When a clock
73 The 0 period value is converted to 0 in hertz and vice versa. 0 always means
148 At creation, the period of the clock is 0: the clock is disabled. You can
151 Note that if you are creating a clock with a fixed period which will never
184  * ``ClockPreUpdate`` : called when the input clock's period is about to
186    which it needs to know the old value of the clock period. During
188    ``clock_ticks_to_ns()`` will use the old period.
189  * ``ClockUpdate`` : called after the input clock's period has changed.
191    will use the new period.
219 configures ``clk2`` to follow the ``clk1`` period changes. Every time ``clk1``
258 clocks get the new clock period value: *Clock 2*, *Clock 3* and *Clock 4*.
267 clocks run with the same period as their source (parent) clock.
268 The Clock API supports a built-in period multiplier/divider
270 run at a different period from its own. If you call the
273 will all run with a period of ``parent_period * multiplier / divider``.
293 A newly created input clock is disabled (period of 0). This means the
294 clock will be considered as disabled until the period is updated. If
319 or has not yet been configured, in which case the period will be
321 period changes.
323 Fetching clock frequency/period
329 ``clock_get()`` returns the period of the clock in its fully precise
351         /* do something with the new period */
352         fprintf(stdout, "device new period is %" PRIu64 "* 2^-32 ns\n",
361 It's also possible to retrieve the clock period from a QTest by
362 accessing QOM property ``qtest-clock-period`` using a QMP command.
377 shortcut like multiplying a "period of clock in nanoseconds" value
382 For a clock with a very long period and a large number of ticks,
403 (i.e. it has period zero). If the inputs imply a tick count that
405 very short period) the output value is truncated, so effectively
408 Changing a clock period
478 try to change the clock period or set a callback to the clock. This