[libcamera-devel] [PATCH] ipa: rpi: Add hardware line rate constraints

[Naushir Patuck]

Advertise hardware constraints on the pixel processing rate through the
Controller::HardwareConfig structure. When calculating the minimum line
length during a configure() operation, ensure that we don't exceed this
constraint.

If we do exceed the hardware constraints, increase the modes's minimum
line length so the pixel processing rate falls below the hardware limit.
If this is not possible, throw a loud error message in the logs.

Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
---
 src/ipa/rpi/common/ipa_base.cpp       | 26 ++++++++++++++++++++++++++
 src/ipa/rpi/controller/controller.cpp |  3 +++
 src/ipa/rpi/controller/controller.h   |  2 ++
 3 files changed, 31 insertions(+)

diff --git a/src/ipa/rpi/common/ipa_base.cpp b/src/ipa/rpi/common/ipa_base.cpp
index 6ac9d5de2f88..419f19f120da 100644
--- a/src/ipa/rpi/common/ipa_base.cpp
+++ b/src/ipa/rpi/common/ipa_base.cpp
@@ -531,6 +531,32 @@ void IpaBase::setMode(const IPACameraSensorInfo &sensorInfo)
 	mode_.minLineLength = sensorInfo.minLineLength * (1.0s / sensorInfo.pixelRate);
 	mode_.maxLineLength = sensorInfo.maxLineLength * (1.0s / sensorInfo.pixelRate);
 
+	/*
+	 * Ensure that the maximum pixel processing rate does not exceed the ISP
+	 * hardware capabilities. If it does, try adjusting the minimum line
+	 * length to compensate if possible.
+	 */
+	Duration minPixelTime = controller_.getHardwareConfig().minPixelProcessingTime;
+	Duration pixelTime = mode_.minLineLength / mode_.width;
+	if (minPixelTime && pixelTime < minPixelTime) {
+		Duration adjustedLineLength = minPixelTime * mode_.width;
+		if (adjustedLineLength <= mode_.maxLineLength) {
+			LOG(IPARPI, Info)
+				<< "Adjusting mode minimum line length from " << mode_.minLineLength
+				<< " to " << adjustedLineLength << " because of HW constraints.";
+			mode_.minLineLength = adjustedLineLength;
+		} else {
+			LOG(IPARPI, Error)
+				<< "Sensor minimum line length of " << pixelTime * mode_.width
+				<< " (" << 1us / pixelTime << " MPix/s)"
+				<< " is below the minimum allowable HW limit of " << minPixelTime * mode_.width
+				<< " (" << 1us / minPixelTime << " MPix/s) ";
+			LOG(IPARPI, Error)
+				<< "THIS WILL CAUSE IMAGE CORRUPTION!!! "
+				<< "Please update the driver to allow more horizontal blanking control.";
+		}
+	}
+
 	/*
 	 * Set the frame length limits for the mode to ensure exposure and
 	 * framerate calculations are clipped appropriately.
diff --git a/src/ipa/rpi/controller/controller.cpp b/src/ipa/rpi/controller/controller.cpp
index e62becd87e85..f81edf769736 100644
--- a/src/ipa/rpi/controller/controller.cpp
+++ b/src/ipa/rpi/controller/controller.cpp
@@ -17,6 +17,7 @@
 
 using namespace RPiController;
 using namespace libcamera;
+using namespace std::literals::chrono_literals;
 
 LOG_DEFINE_CATEGORY(RPiController)
 
@@ -37,6 +38,7 @@ static const std::map<std::string, Controller::HardwareConfig> HardwareConfigMap
 			.numGammaPoints = 33,
 			.pipelineWidth = 13,
 			.statsInline = false,
+			.minPixelProcessingTime = 0s,
 		}
 	},
 	{
@@ -51,6 +53,7 @@ static const std::map<std::string, Controller::HardwareConfig> HardwareConfigMap
 			.numGammaPoints = 64,
 			.pipelineWidth = 16,
 			.statsInline = true,
+			.minPixelProcessingTime = 1.0us / 380, /* 380 MPix/s */
 		}
 	},
 };
diff --git a/src/ipa/rpi/controller/controller.h b/src/ipa/rpi/controller/controller.h
index 6e5f595284fd..170aea740789 100644
--- a/src/ipa/rpi/controller/controller.h
+++ b/src/ipa/rpi/controller/controller.h
@@ -15,6 +15,7 @@
 #include <vector>
 #include <string>
 
+#include <libcamera/base/utils.h>
 #include "libcamera/internal/yaml_parser.h"
 
 #include "camera_mode.h"
@@ -47,6 +48,7 @@ public:
 		unsigned int numGammaPoints;
 		unsigned int pipelineWidth;
 		bool statsInline;
+		libcamera::utils::Duration minPixelProcessingTime;
 	};
 
 	Controller();
-- 
2.34.1