[libcamera-devel] [PATCH] ipa: ipu3: af: enforce grid size restrictions

[Kieran Bingham]

Provide enforcement of the selection of the block_{width,height}_log2
parameters to the capabilities of the hardware.

While this selection is currently hardcoded to the minimum, providing
the restriction now allows for further dynamic sizing in the future and
documents the restrictions directly in code, making use of the already
existing constants.

Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
---

Note, this is kept separate from my other AF improvement series, as it
can be applied independantly - but due to a compilation failure if
kAfMinGridBlockWidth, kAfMaxGridBlockWidth kAfMinGridBlockHeight, and
kAfMaxGridBlockHeight are not used, this patch must be applied before
that series can be integrated.

 src/ipa/ipu3/algorithms/af.cpp | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/src/ipa/ipu3/algorithms/af.cpp b/src/ipa/ipu3/algorithms/af.cpp
index 6c25d02ec7f0..abfaad6164f1 100644
--- a/src/ipa/ipu3/algorithms/af.cpp
+++ b/src/ipa/ipu3/algorithms/af.cpp
@@ -139,6 +139,22 @@ int Af::configure(IPAContext &context, const IPAConfigInfo &configInfo)
 	grid.height = kAfMinGridHeight;
 	grid.block_width_log2 = kAfMinGridBlockWidth;
 	grid.block_height_log2 = kAfMinGridBlockHeight;
+
+	/*
+	 * \todo - while this clamping code is effectively a no-op, it satisfies
+	 * the compiler that the definitions regarding the hardware restrictions
+	 * are used, and paves the way to support dynamic grid sizing in the
+	 * future. While the block_{width,height}_log2 remain assigned to the
+	 * minimum, this code should be optimized out by the compiler.
+	 */
+	grid.block_width_log2 = std::clamp(grid.block_width_log2,
+					   kAfMinGridBlockWidth,
+					   kAfMaxGridBlockWidth);
+
+	grid.block_height_log2 = std::clamp(grid.block_height_log2,
+					    kAfMinGridBlockHeight,
+					    kAfMaxGridBlockHeight);
+
 	grid.height_per_slice = kAfDefaultHeightPerSlice;
 
 	/* Position the AF grid in the center of the BDS output. */
-- 
2.32.0