libcamera: raspberrypi: Add control of sensor vblanking

Add support for setting V4L2_CID_VBLANK appropriately when setting
V4L2_CID_EXPOSURE. This will allow adaptive framerates during
viewfinder use cases (e.g. when the exposure time goes above 33ms, we
can reduce the framerate to lower than 30fps).

The minimum and maximum frame durations are provided via libcamera
controls, and will prioritise exposure time limits over any AGC request.

V4L2_CID_VBLANK is controlled through the staggered writer, just like
the exposure and gain controls.

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
Tested-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 49 insertions, 7 deletions

diff --git a/src/ipa/raspberrypi/raspberrypi.cpp b/src/ipa/raspberrypi/raspberrypi.cpp
index 8af3d603..5ccc7a65 100644
--- a/src/ipa/raspberrypi/raspberrypi.cpp
+++ b/src/ipa/raspberrypi/raspberrypi.cpp
@@ -58,6 +58,8 @@ namespace libcamera {
 /* Configure the sensor with these values initially. */
 constexpr double DefaultAnalogueGain = 1.0;
 constexpr unsigned int DefaultExposureTime = 20000;
+constexpr double defaultMinFrameDuration = 1e6 / 30.0;
+constexpr double defaultMaxFrameDuration = 1e6 / 0.01;
 
 LOG_DEFINE_CATEGORY(IPARPI)
 
@@ -150,6 +152,10 @@ private:
 
 	/* Distinguish the first camera start from others. */
 	bool firstStart_;
+
+	/* Frame duration (1/fps) limits, given in microseconds. */
+	double minFrameDuration_;
+	double maxFrameDuration_;
 };
 
 int IPARPi::init(const IPASettings &settings)
@@ -332,7 +338,8 @@ void IPARPi::configure(const CameraSensorInfo &sensorInfo,
 		sensorMetadata = helper_->SensorEmbeddedDataPresent();
 
 		result->data.push_back(gainDelay);
-		result->data.push_back(exposureDelay);
+		result->data.push_back(exposureDelay); /* For EXPOSURE ctrl */
+		result->data.push_back(exposureDelay); /* For VBLANK ctrl */
 		result->data.push_back(sensorMetadata);
 
 		result->operation |= RPi::IPA_CONFIG_STAGGERED_WRITE;
@@ -377,6 +384,9 @@ void IPARPi::configure(const CameraSensorInfo &sensorInfo,
 		controller_.Initialise();
 		controllerInit_ = true;
 
+		minFrameDuration_ = defaultMinFrameDuration;
+		maxFrameDuration_ = defaultMaxFrameDuration;
+
 		/* Supply initial values for gain and exposure. */
 		ControlList ctrls(sensorCtrls_);
 		AgcStatus agcStatus;
@@ -526,7 +536,8 @@ bool IPARPi::validateSensorControls()
 {
 	static const uint32_t ctrls[] = {
 		V4L2_CID_ANALOGUE_GAIN,
-		V4L2_CID_EXPOSURE
+		V4L2_CID_EXPOSURE,
+		V4L2_CID_VBLANK,
 	};
 
 	for (auto c : ctrls) {
@@ -553,7 +564,7 @@ bool IPARPi::validateIspControls()
 		V4L2_CID_USER_BCM2835_ISP_DENOISE,
 		V4L2_CID_USER_BCM2835_ISP_SHARPEN,
 		V4L2_CID_USER_BCM2835_ISP_DPC,
-		V4L2_CID_USER_BCM2835_ISP_LENS_SHADING
+		V4L2_CID_USER_BCM2835_ISP_LENS_SHADING,
 	};
 
 	for (auto c : ctrls) {
@@ -806,6 +817,25 @@ void IPARPi::queueRequest(const ControlList &controls)
 			break;
 		}
 
+		case controls::FRAME_DURATIONS: {
+			auto frameDurations = ctrl.second.get<Span<const int64_t>>();
+
+			/* This will be applied once AGC recalculations occur. */
+			minFrameDuration_ = frameDurations[0] ? frameDurations[0] : defaultMinFrameDuration;
+			maxFrameDuration_ = frameDurations[1] ? frameDurations[1] : defaultMaxFrameDuration;
+			maxFrameDuration_ = std::max(maxFrameDuration_, minFrameDuration_);
+
+			/*
+			 * \todo The values returned in the metadata below must be
+			 * correctly clipped by what the sensor mode supports and
+			 * what the AGC exposure mode or manual shutter speed limits
+			 */
+			libcameraMetadata_.set(controls::FrameDurations,
+					       { static_cast<int64_t>(minFrameDuration_),
+						 static_cast<int64_t>(maxFrameDuration_) });
+			break;
+		}
+
 		default:
 			LOG(IPARPI, Warning)
 				<< "Ctrl " << controls::controls.at(ctrl.first)->name()
@@ -964,15 +994,27 @@ void IPARPi::applyAWB(const struct AwbStatus *awbStatus, ControlList &ctrls)
 void IPARPi::applyAGC(const struct AgcStatus *agcStatus, ControlList &ctrls)
 {
 	int32_t gainCode = helper_->GainCode(agcStatus->analogue_gain);
-	int32_t exposureLines = helper_->ExposureLines(agcStatus->shutter_time);
 
-	LOG(IPARPI, Debug) << "Applying AGC Exposure: " << agcStatus->shutter_time
-			   << " (Shutter lines: " << exposureLines << ") Gain: "
+	/* GetVBlanking might clip exposure time to the fps limits. */
+	double exposure = agcStatus->shutter_time;
+	int32_t vblanking = helper_->GetVBlanking(exposure, minFrameDuration_,
+						  maxFrameDuration_);
+	int32_t exposureLines = helper_->ExposureLines(exposure);
+
+	LOG(IPARPI, Debug) << "Applying AGC Exposure: " << exposure
+			   << " (Shutter lines: " << exposureLines << ", AGC requested "
+			   << agcStatus->shutter_time << ") Gain: "
 			   << agcStatus->analogue_gain << " (Gain Code: "
 			   << gainCode << ")";
 
-	ctrls.set(V4L2_CID_ANALOGUE_GAIN, gainCode);
+	/*
+	 * Due to the behavior of V4L2, the current value of VBLANK could clip the
+	 * exposure time without us knowing. The next time though this function should
+	 * clip exposure correctly.
+	 */
+	ctrls.set(V4L2_CID_VBLANK, vblanking);
 	ctrls.set(V4L2_CID_EXPOSURE, exposureLines);
+	ctrls.set(V4L2_CID_ANALOGUE_GAIN, gainCode);
 }
 
 void IPARPi::applyDG(const struct AgcStatus *dgStatus, ControlList &ctrls)