libcamera: controls: Use nanoseconds units for FrameWallClock

Use nanoseconds for the FrameWallClock control to match the units for
other timestamp controls, including SensorTimestamp.

Update the RPi pipeline handlers to match the new nanoseconds units when
converting from SensorTimestamp to FrameWallClock.

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/libcamera/control_ids_core.yaml

@@ -1274,7 +1274,8 @@ controls:
       description: |
         This timestamp corresponds to the same moment in time as the
         SensorTimestamp, but is represented as a wall clock time as measured by
-        the CLOCK_REALTIME clock.
+        the CLOCK_REALTIME clock. Like SensorTimestamp, the timestamp value is
+        expressed in nanoseconds.
 
         Being a wall clock measurement, it can be used to synchronise timing
         across different devices.

src/libcamera/pipeline/rpi/pisp/pisp.cpp

@@ -1760,7 +1760,7 @@ void PiSPCameraData::cfeBufferDequeue(FrameBuffer *buffer)
 		 */
 		wallClockRecovery_.addSample();
 		uint64_t sensorTimestamp = buffer->metadata().timestamp;
-		uint64_t wallClockTimestamp = wallClockRecovery_.getOutput(sensorTimestamp / 1000);
+		uint64_t wallClockTimestamp = wallClockRecovery_.getOutput(sensorTimestamp);
 
 		ctrl.set(controls::SensorTimestamp, sensorTimestamp);
 		ctrl.set(controls::FrameWallClock, wallClockTimestamp);

src/libcamera/pipeline/rpi/vc4/vc4.cpp

@@ -778,7 +778,7 @@ void Vc4CameraData::unicamBufferDequeue(FrameBuffer *buffer)
 		 */
 		wallClockRecovery_.addSample();
 		uint64_t sensorTimestamp = buffer->metadata().timestamp;
-		uint64_t wallClockTimestamp = wallClockRecovery_.getOutput(sensorTimestamp / 1000);
+		uint64_t wallClockTimestamp = wallClockRecovery_.getOutput(sensorTimestamp);
 
 		ctrl.set(controls::SensorTimestamp, sensorTimestamp);
 		ctrl.set(controls::FrameWallClock, wallClockTimestamp);