Add a new callback event type ClockPreUpdate, which is called
on period changes before the period is updated.
Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
---
docs/devel/clocks.rst | 9 ++++++++-
include/hw/clock.h | 1 +
hw/core/clock.c | 3 +++
3 files changed, 12 insertions(+), 1 deletion(-)
diff --git a/docs/devel/clocks.rst b/docs/devel/clocks.rst
index 8d3b456561f..dea63742fb0 100644
--- a/docs/devel/clocks.rst
+++ b/docs/devel/clocks.rst
@@ -179,7 +179,14 @@ specific events they need to handle, so that if in future
different
events are added the callback code doesn't need to be updated.
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.
Retrieving clocks from a device
-------------------------------
diff --git a/include/hw/clock.h b/include/hw/clock.h
index 323f8d49fed..7d0eb286faa 100644
--- a/include/hw/clock.h
+++ b/include/hw/clock.h
@@ -27,6 +27,7 @@ OBJECT_DECLARE_SIMPLE_TYPE(Clock, CLOCK)
* has been called.
*/
typedef enum ClockEvent {
+ ClockPreUpdate, /* Clock period is about to update */
ClockUpdate, /* Clock period has just updated */
} ClockEvent;
diff --git a/hw/core/clock.c b/hw/core/clock.c
index 772d03a2eb5..963fe83a363 100644
--- a/hw/core/clock.c
+++ b/hw/core/clock.c
@@ -68,6 +68,9 @@ static void clock_propagate_period(Clock *clk, bool
call_callbacks)
QLIST_FOREACH(child, &clk->children, sibling) {
if (child->period != clk->period) {
+ if (call_callbacks && child->callback) {
+ child->callback(child->callback_opaque, ClockPreUpdate);
+ }
child->period = clk->period;
trace_clock_update(CLOCK_PATH(child), CLOCK_PATH(clk),
CLOCK_PERIOD_TO_HZ(clk->period),
--
2.20.1
