ipa: raspberrypi: Generalise the contrast algorithm

Generalise the contrast algorithm code by removing any hard-coded
assumptions about the target hardware platform. Instead, the algorithm
code creates a generic Pwl that gets returned to the IPA, where it gets
converted to the bcm2835 hardware specific lookup table.

As a drive-by, remove an unused mutex.

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/ipa/raspberrypi/controller/contrast_status.h

@@ -6,20 +6,15 @@
  */
 #pragma once
 
+#include "pwl.h"
+
 /*
  * The "contrast" algorithm creates a gamma curve, optionally doing a little bit
  * of contrast stretching based on the AGC histogram.
  */
 
-constexpr unsigned int ContrastNumPoints = 33;
-
-struct ContrastPoint {
-	uint16_t x;
-	uint16_t y;
-};
-
 struct ContrastStatus {
-	struct ContrastPoint points[ContrastNumPoints];
+	RPiController::Pwl gammaCurve;
 	double brightness;
 	double contrast;
 };

src/ipa/raspberrypi/controller/rpi/contrast.cpp

@@ -65,34 +65,19 @@ void Contrast::setContrast(double contrast)
 	contrast_ = contrast;
 }
 
-static void fillInStatus(ContrastStatus &status, double brightness,
-			 double contrast, Pwl &gammaCurve)
-{
-	status.brightness = brightness;
-	status.contrast = contrast;
-	for (unsigned int i = 0; i < ContrastNumPoints - 1; i++) {
-		int x = i < 16 ? i * 1024
-			       : (i < 24 ? (i - 16) * 2048 + 16384
-					 : (i - 24) * 4096 + 32768);
-		status.points[i].x = x;
-		status.points[i].y = std::min(65535.0, gammaCurve.eval(x));
-	}
-	status.points[ContrastNumPoints - 1].x = 65535;
-	status.points[ContrastNumPoints - 1].y = 65535;
-}
-
 void Contrast::initialise()
 {
 	/*
 	 * Fill in some default values as Prepare will run before Process gets
 	 * called.
 	 */
-	fillInStatus(status_, brightness_, contrast_, config_.gammaCurve);
+	status_.brightness = brightness_;
+	status_.contrast = contrast_;
+	status_.gammaCurve = config_.gammaCurve;
 }
 
 void Contrast::prepare(Metadata *imageMetadata)
 {
-	std::unique_lock<std::mutex> lock(mutex_);
 	imageMetadata->set("contrast.status", status_);
 }
 
@@ -183,12 +168,9 @@ void Contrast::process(StatisticsPtr &stats,
 	 * And fill in the status for output. Use more points towards the bottom
 	 * of the curve.
 	 */
-	ContrastStatus status;
+	status_.brightness = brightness_;
-	fillInStatus(status, brightness_, contrast_, gammaCurve);
+	status_.contrast = contrast_;
-	{
+	status_.gammaCurve = std::move(gammaCurve);
-		std::unique_lock<std::mutex> lock(mutex_);
-		status_ = status;
-	}
 }
 
 /* Register algorithm with the system. */

src/ipa/raspberrypi/controller/rpi/contrast.h

@@ -46,7 +46,6 @@ private:
 	double brightness_;
 	double contrast_;
 	ContrastStatus status_;
-	std::mutex mutex_;
 };
 
 } /* namespace RPiController */

src/ipa/raspberrypi/raspberrypi.cpp

@@ -1593,14 +1593,21 @@ void IPARPi::applyCCM(const struct CcmStatus *ccmStatus, ControlList &ctrls)
 
 void IPARPi::applyGamma(const struct ContrastStatus *contrastStatus, ControlList &ctrls)
 {
+	const unsigned int numGammaPoints = controller_.getHardwareConfig().numGammaPoints;
 	struct bcm2835_isp_gamma gamma;
 
-	gamma.enabled = 1;
+	for (unsigned int i = 0; i < numGammaPoints - 1; i++) {
-	for (unsigned int i = 0; i < ContrastNumPoints; i++) {
+		int x = i < 16 ? i * 1024
-		gamma.x[i] = contrastStatus->points[i].x;
+			       : (i < 24 ? (i - 16) * 2048 + 16384
-		gamma.y[i] = contrastStatus->points[i].y;
+					 : (i - 24) * 4096 + 32768);
+		gamma.x[i] = x;
+		gamma.y[i] = std::min<uint16_t>(65535, contrastStatus->gammaCurve.eval(x));
 	}
 
+	gamma.x[numGammaPoints - 1] = 65535;
+	gamma.y[numGammaPoints - 1] = 65535;
+	gamma.enabled = 1;
+
 	ControlValue c(Span<const uint8_t>{ reinterpret_cast<uint8_t *>(&gamma),
 					    sizeof(gamma) });
 	ctrls.set(V4L2_CID_USER_BCM2835_ISP_GAMMA, c);