[PATCH v3 3/6] ipa: rkisp1: blc: Query black levels from camera sensor helper

[Stefan Klug]

As the camera sensor helper now has the ability to provide the black
level, use it. Black levels can still be overwritten by the tuning
file, but the direction is to remove them from the tuning files and move
them into the sensor helpers.

Additionally interpret all values based on 16bits. The conversion to the
scale required by the hardware is done in process(). It ensures all the
values inside libcamera are the same scale and is in preparation for the
i.MX8MP where black levels are based on a 20bit scale. Note that this
breaks existing tuning files. The tuning files distributed with
libcamera will be fixed in a later patch.

Signed-off-by: Stefan Klug <stefan.klug at ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 src/ipa/rkisp1/algorithms/blc.cpp | 54 ++++++++++++++++++++++++++-----
 1 file changed, 46 insertions(+), 8 deletions(-)

diff --git a/src/ipa/rkisp1/algorithms/blc.cpp b/src/ipa/rkisp1/algorithms/blc.cpp
index d2e743541c99..b17b549c55df 100644
--- a/src/ipa/rkisp1/algorithms/blc.cpp
+++ b/src/ipa/rkisp1/algorithms/blc.cpp
@@ -46,10 +46,47 @@ BlackLevelCorrection::BlackLevelCorrection()
 int BlackLevelCorrection::init([[maybe_unused]] IPAContext &context,
 			       const YamlObject &tuningData)
 {
-	blackLevelRed_ = tuningData["R"].get<int16_t>(256);
-	blackLevelGreenR_ = tuningData["Gr"].get<int16_t>(256);
-	blackLevelGreenB_ = tuningData["Gb"].get<int16_t>(256);
-	blackLevelBlue_ = tuningData["B"].get<int16_t>(256);
+	std::optional<int16_t> levelRed = tuningData["R"].get<int16_t>();
+	std::optional<int16_t> levelGreenR = tuningData["Gr"].get<int16_t>();
+	std::optional<int16_t> levelGreenB = tuningData["Gb"].get<int16_t>();
+	std::optional<int16_t> levelBlue = tuningData["B"].get<int16_t>();
+	bool tuningHasLevels = levelRed && levelGreenR && levelGreenB && levelBlue;
+
+	auto blackLevel = context.camHelper->blackLevel();
+	if (!blackLevel) {
+		/*
+		 * Not all camera sensor helpers have been updated with black
+		 * levels. Print a warning and fall back to the levels from the
+		 * tuning data to preserve backward compatibility. This should
+		 * be removed once all helpers provide the data.
+		 */
+		LOG(RkISP1Blc, Warning)
+			<< "No black levels provided by camera sensor helper"
+			<< ", please fix";
+
+		blackLevelRed_ = levelRed.value_or(4096);
+		blackLevelGreenR_ = levelGreenR.value_or(4096);
+		blackLevelGreenB_ = levelGreenB.value_or(4096);
+		blackLevelBlue_ = levelBlue.value_or(4096);
+	} else if (tuningHasLevels) {
+		/*
+		 * If black levels are provided in the tuning file, use them to
+		 * avoid breaking existing camera tuning. This is deprecated and
+		 * will be removed.
+		 */
+		LOG(RkISP1Blc, Warning)
+			<< "Deprecated: black levels overwritten by tuning file";
+
+		blackLevelRed_ = *levelRed;
+		blackLevelGreenR_ = *levelGreenR;
+		blackLevelGreenB_ = *levelGreenB;
+		blackLevelBlue_ = *levelBlue;
+	} else {
+		blackLevelRed_ = *blackLevel;
+		blackLevelGreenR_ = *blackLevel;
+		blackLevelGreenB_ = *blackLevel;
+		blackLevelBlue_ = *blackLevel;
+	}
 
 	tuningParameters_ = true;
 
@@ -77,10 +114,11 @@ void BlackLevelCorrection::prepare([[maybe_unused]] IPAContext &context,
 		return;
 
 	params->others.bls_config.enable_auto = 0;
-	params->others.bls_config.fixed_val.r = blackLevelRed_;
-	params->others.bls_config.fixed_val.gr = blackLevelGreenR_;
-	params->others.bls_config.fixed_val.gb = blackLevelGreenB_;
-	params->others.bls_config.fixed_val.b = blackLevelBlue_;
+	/* The rkisp1 uses 12bit based black levels. Scale down accordingly. */
+	params->others.bls_config.fixed_val.r = blackLevelRed_ >> 4;
+	params->others.bls_config.fixed_val.gr = blackLevelGreenR_ >> 4;
+	params->others.bls_config.fixed_val.gb = blackLevelGreenB_ >> 4;
+	params->others.bls_config.fixed_val.b = blackLevelBlue_ >> 4;
 
 	params->module_en_update |= RKISP1_CIF_ISP_MODULE_BLS;
 	params->module_ens |= RKISP1_CIF_ISP_MODULE_BLS;
-- 
2.43.0