Decompand initial values

src/ipa/rpi/controller/decompand_algorithm.h

@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+ * Copyright (C) 2025, Raspberry Pi Ltd
+ *
+ * Decompand control algorithm interface
+ */
+#pragma once
+
+#include "libipa/pwl.h"
+
+#include "algorithm.h"
+
+namespace RPiController {
+
+class DecompandAlgorithm : public Algorithm
+{
+public:
+	DecompandAlgorithm(Controller *controller = NULL)
+		: 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

@@ -13,7 +13,7 @@ LOG_DEFINE_CATEGORY(RPiDecompand)
 #define NAME "rpi.decompand"
 
 Decompand::Decompand(Controller *controller)
-	: Algorithm(controller)
+	: DecompandAlgorithm(controller)
 {
 }
 
@@ -39,6 +39,14 @@ void Decompand::switchMode([[maybe_unused]] 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

@@ -2,25 +2,25 @@
 
 #include <libipa/pwl.h>
 
+#include "../decompand_algorithm.h"
 #include "../decompand_status.h"
 
-#include "algorithm.h"
-
 namespace RPiController {
 
 struct DecompandConfig {
 	uint32_t bitdepth;
 	libcamera::ipa::Pwl decompandCurve;
 };
 
-class Decompand : public Algorithm
+class Decompand : public DecompandAlgorithm
 {
 public:
 	Decompand(Controller *controller = NULL);
 	char const *name() const override;
 	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"
@@ -256,7 +257,7 @@ class IpaPiSP final : public IpaBase
 	void applyLensShading(const AlscStatus *alscStatus,
 			      pisp_be_global_config &global);
 	void applyDPC(const DpcStatus *dpcStatus, pisp_be_global_config &global);
-	void applyDecompand(const DecompandStatus *decompandStatus);
+	void applyDecompand(const DecompandStatus *decompandStatus, pisp_fe_global_config &feGlobal);
 	void applySdn(const SdnStatus *sdnStatus, pisp_be_global_config &global);
 	void applyTdn(const TdnStatus *tdnStatus, const DeviceStatus *deviceStatus,
 		      pisp_be_global_config &global);
@@ -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;
 }
 
@@ -368,20 +383,24 @@ void IpaPiSP::platformPrepareIsp([[maybe_unused]] const PrepareParams &params,
 	{
 		/* All Frontend config goes first, we do not want to hold the FE lock for long! */
 		std::scoped_lock<FrontEnd> lf(*fe_);
+		pisp_fe_global_config feGlobal;
+
+		fe_->GetGlobal(feGlobal);
 
 		if (noiseStatus)
 			applyFocusStats(noiseStatus);
 
 		DecompandStatus *decompandStatus =
 			rpiMetadata.getLocked<DecompandStatus>("decompand.status");
 		if (decompandStatus)
-			applyDecompand(decompandStatus);
+			applyDecompand(decompandStatus, feGlobal);
 
 		BlackLevelStatus *blackLevelStatus =
 			rpiMetadata.getLocked<BlackLevelStatus>("black_level.status");
 		if (blackLevelStatus)
 			applyBlackLevel(blackLevelStatus, global);
 
+		fe_->SetGlobal(feGlobal);
 	}
 
 	CacStatus *cacStatus = rpiMetadata.getLocked<CacStatus>("cac.status");
@@ -728,18 +747,15 @@ void IpaPiSP::applyDPC(const DpcStatus *dpcStatus, pisp_be_global_config &global
 	be_->SetDpc(dpc);
 }
 
-void IpaPiSP::applyDecompand(const DecompandStatus *decompandStatus)
+void IpaPiSP::applyDecompand(const DecompandStatus *decompandStatus, pisp_fe_global_config &feGlobal)
 {
-	pisp_fe_global_config feGlobal;
 	pisp_fe_decompand_config decompand = {};
 
-	fe_->GetGlobal(feGlobal);
-
 	if (!generateDecompandLut(decompandStatus->decompandCurve, decompand.lut, PISP_FE_DECOMPAND_LUT_SIZE)) {
 		fe_->SetDecompand(decompand);
 		feGlobal.enables |= PISP_FE_ENABLE_DECOMPAND;
-		fe_->SetGlobal(feGlobal);
-	}
+	} else
+		feGlobal.enables &= ~PISP_FE_ENABLE_DECOMPAND;
 }
 
 void IpaPiSP::applySdn(const SdnStatus *sdnStatus, pisp_be_global_config &global)