[libcamera-devel] [PATCH 3/4] ipa: raspberrypi: Add camera helper for Sony IMX296 sensor

[Laurent Pinchart]

From: Naushir Patuck <naush at raspberrypi.com>

The Sony IMX296 sensor has an exponential gain model, and adds a fixed
14.26µs offset to the exposure time expressed in line units.

Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 src/ipa/raspberrypi/cam_helper_imx296.cpp | 126 ++++++++++++++++++++++
 src/ipa/raspberrypi/meson.build           |   1 +
 2 files changed, 127 insertions(+)
 create mode 100644 src/ipa/raspberrypi/cam_helper_imx296.cpp

diff --git a/src/ipa/raspberrypi/cam_helper_imx296.cpp b/src/ipa/raspberrypi/cam_helper_imx296.cpp
new file mode 100644
index 000000000000..9c34582861f1
--- /dev/null
+++ b/src/ipa/raspberrypi/cam_helper_imx296.cpp
@@ -0,0 +1,126 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+ * Copyright (C) 2020, Raspberry Pi (Trading) Limited
+ *
+ * cam_helper_imx296.cpp - camera helper for imx296 sensor
+ */
+
+#include <assert.h>
+#include <cmath>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+/*
+ * We have observed the imx296 embedded data stream randomly return junk
+ * reister values.  Do not rely on embedded data until this has been resolved.
+ */
+#define ENABLE_EMBEDDED_DATA 0
+
+#include "cam_helper.hpp"
+#if ENABLE_EMBEDDED_DATA
+#include "md_parser.hpp"
+#endif
+
+//#include "imx296_gain_table.hpp"
+
+using namespace RPiController;
+using libcamera::utils::Duration;
+using namespace std::literals::chrono_literals;
+
+/*
+ * We care about one gain register and a pair of exposure registers. Their I2C
+ * addresses from the Sony IMX296 datasheet:
+ */
+constexpr uint32_t gainReg = 0x157;
+constexpr uint32_t expHiReg = 0x15a;
+constexpr uint32_t expLoReg = 0x15b;
+constexpr std::initializer_list<uint32_t> registerList [[maybe_unused]] = { expHiReg, expLoReg, gainReg };
+
+class CamHelperImx296 : public CamHelper
+{
+public:
+	CamHelperImx296();
+	uint32_t GainCode(double gain) const override;
+	double Gain(uint32_t gain_code) const override;
+	uint32_t ExposureLines(Duration exposure) const override;
+	Duration Exposure(uint32_t exposure_lines) const override;
+	unsigned int MistrustFramesModeSwitch() const override;
+	bool SensorEmbeddedDataPresent() const override;
+
+private:
+	static constexpr uint32_t maxGainCode = 239;
+	static constexpr Duration timePerLine = 550.0 / 37.125e6 * 1.0s;
+
+	/*
+	 * Smallest difference between the frame length and integration time,
+	 * in units of lines.
+	 */
+	static constexpr int frameIntegrationDiff = 4;
+
+	void PopulateMetadata(const MdParser::RegisterMap &registers,
+			      Metadata &metadata) const override;
+};
+
+CamHelperImx296::CamHelperImx296()
+#if ENABLE_EMBEDDED_DATA
+	: CamHelper(std::make_unique<MdParserSmia>(registerList), frameIntegrationDiff)
+#else
+	: CamHelper(nullptr, frameIntegrationDiff)
+#endif
+{
+}
+
+uint32_t CamHelperImx296::GainCode(double gain) const
+{
+	uint32_t code = 20 * std::log10(gain) * 10;
+	return std::min(code, maxGainCode);
+}
+
+double CamHelperImx296::Gain(uint32_t gain_code) const
+{
+	return std::pow(10.0, gain_code / 200.0);
+}
+
+uint32_t CamHelperImx296::ExposureLines(Duration exposure) const
+{
+	return (exposure - 14.26us) / timePerLine;
+}
+
+Duration CamHelperImx296::Exposure(uint32_t exposure_lines) const
+{
+	return exposure_lines * timePerLine + 14.26us;
+}
+
+unsigned int CamHelperImx296::MistrustFramesModeSwitch() const
+{
+	/*
+	 * For reasons unknown, we do occasionally get a bogus metadata frame
+	 * at a mode switch (though not at start-up). Possibly warrants some
+	 * investigation, though not a big deal.
+	 */
+	return 1;
+}
+
+bool CamHelperImx296::SensorEmbeddedDataPresent() const
+{
+	return ENABLE_EMBEDDED_DATA;
+}
+
+void CamHelperImx296::PopulateMetadata(const MdParser::RegisterMap &registers,
+				       Metadata &metadata) const
+{
+	DeviceStatus deviceStatus;
+
+	deviceStatus.shutter_speed = Exposure(registers.at(expHiReg) * 256 + registers.at(expLoReg));
+	deviceStatus.analogue_gain = Gain(registers.at(gainReg));
+
+	metadata.Set("device.status", deviceStatus);
+}
+
+static CamHelper *Create()
+{
+	return new CamHelperImx296();
+}
+
+static RegisterCamHelper reg("imx296", &Create);
diff --git a/src/ipa/raspberrypi/meson.build b/src/ipa/raspberrypi/meson.build
index 176055f42248..32897e07dad9 100644
--- a/src/ipa/raspberrypi/meson.build
+++ b/src/ipa/raspberrypi/meson.build
@@ -21,6 +21,7 @@ rpi_ipa_sources = files([
     'cam_helper_ov5647.cpp',
     'cam_helper_imx219.cpp',
     'cam_helper_imx290.cpp',
+    'cam_helper_imx296.cpp',
     'cam_helper_imx477.cpp',
     'cam_helper_imx519.cpp',
     'cam_helper_ov9281.cpp',
-- 
Regards,

Laurent Pinchart