From cd3149a7fa84ae237f0bfbe71e8a68794e7fce06 Mon Sep 17 00:00:00 2001
From: Kieran Bingham <kieran.bingham@ideasonboard.com>
Date: Thu, 19 Feb 2026 15:05:04 +0000
Subject: [PATCH] ipa: libipa: fixedpoint: Fix unsigned usage

The fixedToFloatingPoint does not support unsigned Q types, and
incorrectly sign-extends all values which have the top most bit set in
the quantized values.

Fix this by ensuring that only signed types perform sign extension, and
simplify the calculation for unsigned types.

Convert the storage of the test cases to signed types to correctly
represent their intended purpose, to prevent test failures.

Reviewed-by: Isaac Scott <isaac.scott@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
---
 src/ipa/libipa/fixedpoint.h    | 3 +++
 test/ipa/libipa/fixedpoint.cpp | 6 +++---
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/ipa/libipa/fixedpoint.h b/src/ipa/libipa/fixedpoint.h
index 709cf50f..aeb9bce3 100644
--- a/src/ipa/libipa/fixedpoint.h
+++ b/src/ipa/libipa/fixedpoint.h
@@ -49,6 +49,9 @@ constexpr R fixedToFloatingPoint(T number)
 	static_assert(sizeof(int) >= sizeof(T));
 	static_assert(I + F <= sizeof(T) * 8);
 
+	if constexpr (std::is_unsigned_v<T>)
+		return static_cast<R>(number) / static_cast<R>(T{ 1 } << F);
+
 	/*
 	 * Recreate the upper bits in case of a negative number by shifting the sign
 	 * bit from the fixed point to the first bit of the unsigned and then right shifting
diff --git a/test/ipa/libipa/fixedpoint.cpp b/test/ipa/libipa/fixedpoint.cpp
index 99eb662d..4b017e86 100644
--- a/test/ipa/libipa/fixedpoint.cpp
+++ b/test/ipa/libipa/fixedpoint.cpp
@@ -68,7 +68,7 @@ protected:
 		 * The second 7.992 test is to test that unused bits don't
 		 * affect the result.
 		 */
-		std::map<double, uint16_t> testCases = {
+		std::map<double, int16_t> testCases = {
 			{ 7.992, 0x3ff },
 			{   0.2, 0x01a },
 			{  -0.2, 0x7e6 },
@@ -81,14 +81,14 @@ protected:
 
 		int ret;
 		for (const auto &testCase : testCases) {
-			ret = testSingleFixedPoint<4, 7, uint16_t>(testCase.first,
+			ret = testSingleFixedPoint<4, 7, int16_t>(testCase.first,
 								   testCase.second);
 			if (ret != TestPass)
 				return ret;
 		}
 
 		/* Special case with a superfluous one in the unused bits */
-		ret = testFixedToFloat<4, 7, uint16_t, double>(0xbff, 7.992);
+		ret = testFixedToFloat<4, 7, int16_t, double>(0xbff, 7.992);
 		if (ret != TestPass)
 			return ret;