[libcamera-devel] [PATCH v2 07/13] ipa: ipu3: agc: Change analogue gain limits

[Jean-Michel Hautbois]

The gains is currently set as a uint32_t while the analogue gain is
passed as a double. We also have a default maximum analogue gain of 15
which is quite high for a number of sensors.

Use a maximum value of 8 which should really be configured by the IPA
and not fixed as it is now. While at it make it a double.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 src/ipa/ipu3/algorithms/agc.cpp | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp
index 8e1b6d8c..1bae1eb9 100644
--- a/src/ipa/ipu3/algorithms/agc.cpp
+++ b/src/ipa/ipu3/algorithms/agc.cpp
@@ -30,14 +30,10 @@ static constexpr uint32_t kInitialFrameMinAECount = 4;
 /* Number of frames to wait between new gain/exposure estimations */
 static constexpr uint32_t kFrameSkipCount = 6;
 
-/* Maximum ISO value for analogue gain */
-static constexpr uint32_t kMinISO = 100;
-static constexpr uint32_t kMaxISO = 1500;
-
 /* Maximum analogue gain value
  * \todo grab it from a camera helper */
-static constexpr uint32_t kMinGain = kMinISO / 100;
-static constexpr uint32_t kMaxGain = kMaxISO / 100;
+static constexpr double kMinGain = 1.0;
+static constexpr double kMaxGain = 8.0;
 
 /* Histogram constants */
 static constexpr uint32_t knumHistogramBins = 256;
@@ -165,9 +161,11 @@ void Agc::lockExposureGain(uint32_t &exposure, double &gain)
 							minExposureLines_,
 							maxExposureLines_);
 			newExposure = currentExposure_ / exposure;
-			gain = std::clamp(static_cast<uint32_t>(gain * currentExposure_ / newExposure), kMinGain, kMaxGain);
+			gain = std::clamp(gain * currentExposure_ / newExposure,
+					  kMinGain, kMaxGain);
 		} else if (currentShutter >= maxShutterSpeed) {
-			gain = std::clamp(static_cast<uint32_t>(gain * currentExposure_ / currentExposureNoDg_), kMinGain, kMaxGain);
+			gain = std::clamp(gain * currentExposure_ / currentExposureNoDg_,
+					  kMinGain, kMaxGain);
 			newExposure = currentExposure_ / gain;
 			exposure = std::clamp<uint32_t>(exposure * currentExposure_ / newExposure,
 							minExposureLines_,
-- 
2.32.0