ipa: raspberrypi: Limit the maximum sensor gain used

Limit the gain code to the maximum value reported by the sensor controls
when sending to DelayedControls. The AGC algorithm will handle a lower
gain used by the sensor, provided it knows the actual gain used. This
change ensures that DelayedControls will never report an unclipped gain
used.

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: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/src/ipa/raspberrypi/raspberrypi.cpp b/src/ipa/raspberrypi/raspberrypi.cpp
index 0ed41385..a72d516f 100644
--- a/src/ipa/raspberrypi/raspberrypi.cpp
+++ b/src/ipa/raspberrypi/raspberrypi.cpp
@@ -173,6 +173,9 @@ private:
 	/* Frame duration (1/fps) limits. */
 	Duration minFrameDuration_;
 	Duration maxFrameDuration_;
+
+	/* Maximum gain code for the sensor. */
+	uint32_t maxSensorGainCode_;
 };
 
 int IPARPi::init(const IPASettings &settings, ipa::RPi::SensorConfig *sensorConfig)
@@ -357,6 +360,8 @@ int IPARPi::configure(const IPACameraSensorInfo &sensorInfo,
 		return -1;
 	}
 
+	maxSensorGainCode_ = sensorCtrls_.at(V4L2_CID_ANALOGUE_GAIN).max().get<int32_t>();
+
 	/* Setup a metadata ControlList to output metadata. */
 	libcameraMetadata_ = ControlList(controls::controls);
 
@@ -1113,6 +1118,13 @@ void IPARPi::applyAGC(const struct AgcStatus *agcStatus, ControlList &ctrls)
 {
 	int32_t gainCode = helper_->GainCode(agcStatus->analogue_gain);
 
+	/*
+	 * Ensure anything larger than the max gain code will not be passed to
+	 * DelayedControls. The AGC will correctly handle a lower gain returned
+	 * by the sensor, provided it knows the actual gain used.
+	 */
+	gainCode = std::min<int32_t>(gainCode, maxSensorGainCode_);
+
 	/* GetVBlanking might clip exposure time to the fps limits. */
 	Duration exposure = agcStatus->shutter_time;
 	int32_t vblanking = helper_->GetVBlanking(exposure, minFrameDuration_, maxFrameDuration_);