ipa: rpi: pisp: Allow an initial decompand curve to be set on the FE

In the current code, decompand will only set a curve in the prepare
phase, which will only run after 1-2 frames pass through the FE. This
is fixed by adding an initialValues() member function to the decompand
algorithm, which will be called in the IPA before we start the hardware
streaming.

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
Tested-by: Nick Hollinghurst <nick.hollinghurst@raspberrypi.com>
Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/ipa/rpi/controller/decompand_algorithm.h

@@ -19,6 +19,8 @@ public:
 		: Algorithm(controller)
 	{
 	}
+	/* A decompand algorithm must provide the following: */
+	virtual void initialValues(libcamera::ipa::Pwl &decompandCurve) = 0;
 };
 
 } /* namespace RPiController */

src/ipa/rpi/controller/rpi/decompand.cpp

@@ -39,6 +39,14 @@ void Decompand::switchMode(CameraMode const &cameraMode,
 	mode_ = cameraMode;
 }
 
+void Decompand::initialValues(libcamera::ipa::Pwl &decompandCurve)
+{
+	if (config_.bitdepth == 0 || mode_.bitdepth == config_.bitdepth) {
+		decompandCurve = config_.decompandCurve;
+	} else
+		decompandCurve = {};
+}
+
 void Decompand::prepare(Metadata *imageMetadata)
 {
 	DecompandStatus decompandStatus;

src/ipa/rpi/controller/rpi/decompand.h

@@ -20,6 +20,7 @@ public:
 	int read(const libcamera::YamlObject &params) override;
 	void initialise() override;
 	void switchMode(CameraMode const &cameraMode, Metadata *metadata) override;
+	void initialValues(libcamera::ipa::Pwl &decompandCurve) override;
 	void prepare(Metadata *imageMetadata) override;
 
 private:

src/ipa/rpi/pisp/pisp.cpp

@@ -32,6 +32,7 @@
 #include "controller/cac_status.h"
 #include "controller/ccm_status.h"
 #include "controller/contrast_status.h"
+#include "controller/decompand_algorithm.h"
 #include "controller/decompand_status.h"
 #include "controller/denoise_algorithm.h"
 #include "controller/denoise_status.h"
@@ -335,6 +336,20 @@ int32_t IpaPiSP::platformStart([[maybe_unused]] const ControlList &controls,
 	/* Cause the stitch block to be reset correctly. */
 	lastStitchHdrStatus_ = HdrStatus();
 
+	/* Setup a default decompand curve on startup if needed. */
+	RPiController::DecompandAlgorithm *decompand = dynamic_cast<RPiController::DecompandAlgorithm *>(
+		controller_.getAlgorithm("decompand"));
+	if (decompand) {
+		std::scoped_lock<FrontEnd> l(*fe_);
+		pisp_fe_global_config feGlobal;
+		DecompandStatus decompandStatus;
+
+		fe_->GetGlobal(feGlobal);
+		decompand->initialValues(decompandStatus.decompandCurve);
+		applyDecompand(&decompandStatus, feGlobal);
+		fe_->SetGlobal(feGlobal);
+	}
+
 	return 0;
 }