[libcamera-devel] [PATCH 09/12] ipa: ipu3: awb: Use the line stride for the stats

[Jean-Michel Hautbois]

The statistics buffer 'ipu3_uapi_awb_raw_buffer' stores the ImgU
calculation results in a buffer aligned to a multiple of 4. The AWB loop
should take care of it to add the proper offset between lines and avoid
any staircase effect.

It is now no more required to pass the grid configuration context to the
private functions called from process() which simplifies the code flow.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
---
 src/ipa/ipu3/algorithms/awb.cpp | 16 ++++++++--------
 src/ipa/ipu3/algorithms/awb.h   |  7 +++----
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/src/ipa/ipu3/algorithms/awb.cpp b/src/ipa/ipu3/algorithms/awb.cpp
index 8a926691..a5391653 100644
--- a/src/ipa/ipu3/algorithms/awb.cpp
+++ b/src/ipa/ipu3/algorithms/awb.cpp
@@ -172,8 +172,10 @@ int Awb::configure(IPAContext &context,
 		   [[maybe_unused]] const IPAConfigInfo &configInfo)
 {
 	const ipu3_uapi_grid_config &grid = context.configuration.grid.bdsGrid;
+	/* The grid is aligned to the next multiple of 4 */
+	stride_ = (grid.width + 3) / 4 * 4;
 
-	cellsPerZoneX_ = round(grid.width / static_cast<double>(kAwbStatsSizeX));
+	cellsPerZoneX_ = round(stride_ / static_cast<double>(kAwbStatsSizeX));
 	cellsPerZoneY_ = round(grid.height / static_cast<double>(kAwbStatsSizeY));
 
 	/*
@@ -234,8 +236,7 @@ void Awb::generateZones(std::vector<RGB> &zones)
 }
 
 /* Translate the IPU3 statistics into the default statistics zone array */
-void Awb::generateAwbStats(const ipu3_uapi_stats_3a *stats,
-			   const ipu3_uapi_grid_config &grid)
+void Awb::generateAwbStats(const ipu3_uapi_stats_3a *stats)
 {
 	/*
 	 * Generate a (kAwbStatsSizeX x kAwbStatsSizeY) array from the IPU3 grid which is
@@ -243,7 +244,7 @@ void Awb::generateAwbStats(const ipu3_uapi_stats_3a *stats,
 	 */
 	for (unsigned int cellY = 0; cellY < kAwbStatsSizeY * cellsPerZoneY_; cellY++) {
 		for (unsigned int cellX = 0; cellX < kAwbStatsSizeX * cellsPerZoneX_; cellX++) {
-			uint32_t cellPosition = (cellY * grid.width + cellX)
+			uint32_t cellPosition = (cellY * stride_ + cellX)
 					      * sizeof(Ipu3AwbCell);
 			uint32_t zoneX = cellX / cellsPerZoneX_;
 			uint32_t zoneY = cellY / cellsPerZoneY_;
@@ -318,13 +319,12 @@ void Awb::awbGreyWorld()
 	asyncResults_.blueGain = blueGain;
 }
 
-void Awb::calculateWBGains(const ipu3_uapi_stats_3a *stats,
-			   const ipu3_uapi_grid_config &grid)
+void Awb::calculateWBGains(const ipu3_uapi_stats_3a *stats)
 {
 	ASSERT(stats->stats_3a_status.awb_en);
 	zones_.clear();
 	clearAwbStats();
-	generateAwbStats(stats, grid);
+	generateAwbStats(stats);
 	generateZones(zones_);
 	LOG(IPU3Awb, Debug) << "Valid zones: " << zones_.size();
 	if (zones_.size() > 10) {
@@ -336,7 +336,7 @@ void Awb::calculateWBGains(const ipu3_uapi_stats_3a *stats,
 
 void Awb::process(IPAContext &context, const ipu3_uapi_stats_3a *stats)
 {
-	calculateWBGains(stats, context.configuration.grid.bdsGrid);
+	calculateWBGains(stats);
 
 	/*
 	 * Gains are only recalculated if enough zones were detected.
diff --git a/src/ipa/ipu3/algorithms/awb.h b/src/ipa/ipu3/algorithms/awb.h
index 681d8c2b..b3e0ad82 100644
--- a/src/ipa/ipu3/algorithms/awb.h
+++ b/src/ipa/ipu3/algorithms/awb.h
@@ -74,11 +74,9 @@ public:
 	};
 
 private:
-	void calculateWBGains(const ipu3_uapi_stats_3a *stats,
-			      const ipu3_uapi_grid_config &grid);
+	void calculateWBGains(const ipu3_uapi_stats_3a *stats);
 	void generateZones(std::vector<RGB> &zones);
-	void generateAwbStats(const ipu3_uapi_stats_3a *stats,
-			      const ipu3_uapi_grid_config &grid);
+	void generateAwbStats(const ipu3_uapi_stats_3a *stats);
 	void clearAwbStats();
 	void awbGreyWorld();
 	uint32_t estimateCCT(double red, double green, double blue);
@@ -87,6 +85,7 @@ private:
 	Accumulator awbStats_[kAwbStatsSizeX * kAwbStatsSizeY];
 	AwbStatus asyncResults_;
 
+	uint32_t stride_;
 	uint32_t cellsPerZoneX_;
 	uint32_t cellsPerZoneY_;
 	uint32_t cellsPerZoneThreshold_;
-- 
2.30.2