[libcamera-devel] [PATCH 4/4] ipa: ipu3: Calculate frame duration from minimum VBLANK value

[Umang Jain]

Frame duration is hard-coded for CTS as per [1]. Ideally, to accurately
calculate the frame duration, it needs the VBLANK value from every
frame's exposure. However, this particular bit is yet to be implemented
in IPAIPU3.

Meanwhile, we can atleast head in the right direction by not hard
coding the value, instead using the minimum VBLANK value as reported
the sensor. Update the existing \todo, to use the derived VBLANK value
as and when it's available from each frame exposure.

[1] 6c5f3fe6ced7 ("ipa: ipu3: Set output frame duration metadata")

Signed-off-by: Umang Jain <umang.jain at ideasonboard.com>
---

For reference, on `nautilus`:
- minVBlank_ was reported as '104'
- Calculating frame-duration using minVBlank_ came out to be: 34041

---
 src/ipa/ipu3/ipu3.cpp | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/ipa/ipu3/ipu3.cpp b/src/ipa/ipu3/ipu3.cpp
index 97ddb863..db4ec684 100644
--- a/src/ipa/ipu3/ipu3.cpp
+++ b/src/ipa/ipu3/ipu3.cpp
@@ -72,6 +72,7 @@ private:
 	uint32_t gain_;
 	uint32_t minGain_;
 	uint32_t maxGain_;
+	uint32_t minVBlank_;
 
 	/* Interface to the AWB algorithm */
 	std::unique_ptr<IPU3Awb> awbAlgo_;
@@ -162,6 +163,12 @@ void IPAIPU3::configure(const IPAConfigInfo &configInfo)
 		return;
 	}
 
+	const auto itVBlank = ctrls_.find(V4L2_CID_VBLANK);
+	if (itVBlank == ctrls_.end()) {
+		LOG(IPAIPU3, Error) << "Can't find VBLANK control";
+		return;
+	}
+
 	minExposure_ = std::max(itExp->second.min().get<int32_t>(), 1);
 	maxExposure_ = itExp->second.max().get<int32_t>();
 	exposure_ = minExposure_;
@@ -170,6 +177,8 @@ void IPAIPU3::configure(const IPAConfigInfo &configInfo)
 	maxGain_ = itGain->second.max().get<int32_t>();
 	gain_ = minGain_;
 
+	minVBlank_ = itVBlank->second.min().get<int32_t>();
+
 	params_ = {};
 
 	calculateBdsGrid(configInfo.bdsOutputSize);
@@ -273,9 +282,10 @@ void IPAIPU3::parseStatistics(unsigned int frame,
 	if (agcAlgo_->updateControls())
 		setControls(frame);
 
-	/* \todo Populate this with real values */
-	ctrls.set(controls::FrameDuration,
-		  static_cast<int64_t>(33334));
+	/* \todo Use VBlank value calculated from each frame exposure. */
+	int64_t frameDuration = sensorInfo_.lineLength * (minVBlank_ + sensorInfo_.outputSize.height) /
+				(sensorInfo_.pixelRate / 1e6);
+	ctrls.set(controls::FrameDuration, frameDuration);
 
 	IPU3Action op;
 	op.op = ActionMetadataReady;
-- 
2.31.1