[PATCH v2 1/4] ipa: rkisp1: Add gamma algorithm

[Stefan Klug]

Add a gamma algorithm for the rkisp1. It defaults to a gamma of 2.2 which
closely resembles sRGB.  No seperate sRGB mode was implemented because the pwl
that models the gamma curve is so coarse that there is basically no difference
between srgb and gamma=2.2

The gamma algorithm is not enabled by default. This will be done in future
tuning file updates.

Signed-off-by: Stefan Klug <stefan.klug at ideasonboard.com>
---

Note:

This patch breaks the naming conventions. It is implemented inside goc.h/cpp
because the hardware block and params inside the rkisp1 are called "goc". The
class itself is called Gamma, and the algorithm is registered with the name
"Gamma". The idea was that similar functionalities should be named the same
inside the tuning files (even among multipe isps).  It still feels a bit
awkward. So thoughts are welcome :-)


v1 -> v2:
- fixed some style issues
- fail in case of a V12 isp

 src/ipa/rkisp1/algorithms/goc.cpp     | 100 ++++++++++++++++++++++++++
 src/ipa/rkisp1/algorithms/goc.h       |  32 +++++++++
 src/ipa/rkisp1/algorithms/meson.build |   1 +
 3 files changed, 133 insertions(+)
 create mode 100644 src/ipa/rkisp1/algorithms/goc.cpp
 create mode 100644 src/ipa/rkisp1/algorithms/goc.h

diff --git a/src/ipa/rkisp1/algorithms/goc.cpp b/src/ipa/rkisp1/algorithms/goc.cpp
new file mode 100644
index 00000000..6f313820
--- /dev/null
+++ b/src/ipa/rkisp1/algorithms/goc.cpp
@@ -0,0 +1,100 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Ideas On Board
+ *
+ * RkISP1 Gamma out control
+ */
+#include "goc.h"
+
+#include <cmath>
+
+#include <libcamera/base/log.h>
+#include <libcamera/base/utils.h>
+
+#include "libcamera/internal/yaml_parser.h"
+
+#include "linux/rkisp1-config.h"
+
+/**
+ * \file goc.h
+ */
+
+namespace libcamera {
+
+namespace ipa::rkisp1::algorithms {
+
+/**
+ * \class Gamma
+ * \brief RkISP1 Gamma out control
+ *
+ * This algorithm implements the gamma out curve for the RkISP1.
+ * It defaults to a gamma value of 2.2
+ * As gamma is internally represented as a piecewise linear function with only
+ * 16 knots, the difference between gamma=2.2 and sRGB gamma is minimal.
+ * Therefore sRGB gamma was not implemented as special case.
+ *
+ * Useful links:
+ * https://www.cambridgeincolour.com/tutorials/gamma-correction.htm
+ * https://en.wikipedia.org/wiki/SRGB
+ */
+
+LOG_DEFINE_CATEGORY(RkISP1Gamma)
+
+Gamma::Gamma()
+{
+}
+
+/**
+ * \copydoc libcamera::ipa::Algorithm::init
+ */
+int Gamma::init([[maybe_unused]] IPAContext &context,
+		[[maybe_unused]] const YamlObject &tuningData)
+{
+	if (context.hw->numGammaOutSamples !=
+	    RKISP1_CIF_ISP_GAMMA_OUT_MAX_SAMPLES_V10) {
+		LOG(RkISP1Gamma, Error)
+			<< "Gamma is not implemented for RkISP1 V12";
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/**
+ * \copydoc libcamera::ipa::Algorithm::prepare
+ */
+void Gamma::prepare([[maybe_unused]] IPAContext &context,
+		    const uint32_t frame,
+		    [[maybe_unused]] IPAFrameContext &frameContext,
+		    rkisp1_params_cfg *params)
+{
+	/* The logarithmic segments as specified in the reference.
+	 * Plus an additional 0 to make the loop easier
+	 */
+	int segments[] = { 64, 64, 64, 64, 128, 128, 128, 128, 256, 256, 256,
+			   512, 512, 512, 512, 512, 0 };
+	auto gamma_y = params->others.goc_config.gamma_y;
+
+	ASSERT(context.hw->numGammaOutSamples ==
+	       RKISP1_CIF_ISP_GAMMA_OUT_MAX_SAMPLES_V10);
+
+	if (frame > 0)
+		return;
+
+	int x = 0;
+	for (unsigned i = 0; i < context.hw->numGammaOutSamples; i++) {
+		gamma_y[i] = std::pow(x / 4096.0, 1.0 / gamma_) * 1023.0;
+		x += segments[i];
+	}
+
+	params->others.goc_config.mode = RKISP1_CIF_ISP_GOC_MODE_LOGARITHMIC;
+	params->module_en_update |= RKISP1_CIF_ISP_MODULE_GOC;
+	params->module_ens |= RKISP1_CIF_ISP_MODULE_GOC;
+	params->module_cfg_update |= RKISP1_CIF_ISP_MODULE_GOC;
+}
+
+REGISTER_IPA_ALGORITHM(Gamma, "Gamma")
+
+} /* namespace ipa::rkisp1::algorithms */
+
+} /* namespace libcamera */
diff --git a/src/ipa/rkisp1/algorithms/goc.h b/src/ipa/rkisp1/algorithms/goc.h
new file mode 100644
index 00000000..fe7caba3
--- /dev/null
+++ b/src/ipa/rkisp1/algorithms/goc.h
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Ideas On Board
+ *
+ * RkISP1 Gamma out control
+ */
+
+#pragma once
+
+#include "algorithm.h"
+
+namespace libcamera {
+
+namespace ipa::rkisp1::algorithms {
+
+class Gamma : public Algorithm
+{
+public:
+	Gamma();
+	~Gamma() = default;
+
+	int init(IPAContext &context, const YamlObject &tuningData) override;
+	void prepare(IPAContext &context, const uint32_t frame,
+		     IPAFrameContext &frameContext,
+		     rkisp1_params_cfg *params) override;
+
+private:
+	float gamma_ = 2.2;
+};
+
+} /* namespace ipa::rkisp1::algorithms */
+} /* namespace libcamera */
diff --git a/src/ipa/rkisp1/algorithms/meson.build b/src/ipa/rkisp1/algorithms/meson.build
index 93a48329..6ee71a9b 100644
--- a/src/ipa/rkisp1/algorithms/meson.build
+++ b/src/ipa/rkisp1/algorithms/meson.build
@@ -8,6 +8,7 @@ rkisp1_ipa_algorithms = files([
     'dpcc.cpp',
     'dpf.cpp',
     'filter.cpp',
+    'goc.cpp',
     'gsl.cpp',
     'lsc.cpp',
 ])
-- 
2.40.1