diff options
| -rw-r--r-- | docs/devel/clocks.rst | 9 | ||||
| -rw-r--r-- | hw/core/clock.c | 3 | ||||
| -rw-r--r-- | include/hw/clock.h | 1 |
3 files changed, 12 insertions, 1 deletions
diff --git a/docs/devel/clocks.rst b/docs/devel/clocks.rst index cd344e3fe5..f0391e76b4 100644 --- a/docs/devel/clocks.rst +++ b/docs/devel/clocks.rst @@ -181,7 +181,14 @@ events. The events currently supported are: - * ``ClockUpdate`` : called after the input clock's period has changed + * ``ClockPreUpdate`` : called when the input clock's period is about to + update. This is useful if the device needs to do some action for + which it needs to know the old value of the clock period. During + this callback, Clock API functions like ``clock_get()`` or + ``clock_ticks_to_ns()`` will use the old period. + * ``ClockUpdate`` : called after the input clock's period has changed. + During this callback, Clock API functions like ``clock_ticks_to_ns()`` + will use the new period. Note that a clock only has one callback: it is not possible to register different functions for different events. You must register a single diff --git a/hw/core/clock.c b/hw/core/clock.c index 4479eff145..fc5a99683f 100644 --- a/hw/core/clock.c +++ b/hw/core/clock.c @@ -81,6 +81,9 @@ static void clock_propagate_period(Clock *clk, bool call_callbacks) QLIST_FOREACH(child, &clk->children, sibling) { if (child->period != clk->period) { + if (call_callbacks) { + clock_call_callback(child, ClockPreUpdate); + } child->period = clk->period; trace_clock_update(CLOCK_PATH(child), CLOCK_PATH(clk), CLOCK_PERIOD_TO_HZ(clk->period), diff --git a/include/hw/clock.h b/include/hw/clock.h index 282a37f7c5..2ba44e1442 100644 --- a/include/hw/clock.h +++ b/include/hw/clock.h @@ -30,6 +30,7 @@ OBJECT_DECLARE_SIMPLE_TYPE(Clock, CLOCK) */ typedef enum ClockEvent { ClockUpdate = 1, /* Clock period has just updated */ + ClockPreUpdate = 2, /* Clock period is about to update */ } ClockEvent; typedef void ClockCallback(void *opaque, ClockEvent event); |