ipa: rkisp1: Introduce Black Level Correction

In order to have the proper pixel levels, apply a fixed black level
correction, based on the imx219 tuning file in RPi. The value is 4096 on
16 bits, and the pipeline for RkISP1 is on 12 bits, scale it.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Tested-by: Peter Griffin <peter.griffin@linaro.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 57 insertions, 0 deletions

diff --git a/src/ipa/rkisp1/algorithms/blc.cpp b/src/ipa/rkisp1/algorithms/blc.cpp
new file mode 100644
index 00000000..0c5948ff
--- /dev/null
+++ b/src/ipa/rkisp1/algorithms/blc.cpp
@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021-2022, Ideas On Board
+ *
+ * blc.cpp - RkISP1 Black Level Correction control
+ */
+
+#include "blc.h"
+
+/**
+ * \file blc.h
+ */
+
+namespace libcamera {
+
+namespace ipa::rkisp1::algorithms {
+
+/**
+ * \class BlackLevelCorrection
+ * \brief RkISP1 Black Level Correction control
+ *
+ * The pixels output by the camera normally include a black level, because
+ * sensors do not always report a signal level of '0' for black. Pixels at or
+ * below this level should be considered black. To achieve that, the RkISP BLC
+ * algorithm subtracts a configurable offset from all pixels.
+ *
+ * The black level can be measured at runtime from an optical dark region of the
+ * camera sensor, or measured during the camera tuning process. The first option
+ * isn't currently supported.
+ */
+
+/**
+ * \copydoc libcamera::ipa::Algorithm::prepare
+ */
+void BlackLevelCorrection::prepare(IPAContext &context,
+				   rkisp1_params_cfg *params)
+{
+	if (context.frameContext.frameCount > 0)
+		return;
+	/*
+	 * Substract fixed values taken from imx219 tuning file.
+	 * \todo Use a configuration file for it ?
+	 */
+	params->others.bls_config.enable_auto = 0;
+	params->others.bls_config.fixed_val.r = 256;
+	params->others.bls_config.fixed_val.gr = 256;
+	params->others.bls_config.fixed_val.gb = 256;
+	params->others.bls_config.fixed_val.b = 256;
+
+	params->module_en_update |= RKISP1_CIF_ISP_MODULE_BLS;
+	params->module_ens |= RKISP1_CIF_ISP_MODULE_BLS;
+	params->module_cfg_update |= RKISP1_CIF_ISP_MODULE_BLS;
+}
+
+} /* namespace ipa::rkisp1::algorithms */
+
+} /* namespace libcamera */