[PATCH 16/20] drm/amd/display: use clamping rather than truncation for CM fp conversions

[Harry Wentland]

From: Dmytro Laktyushkin <Dmytro.Laktyushkin at amd.com>

Signed-off-by: Dmytro Laktyushkin <Dmytro.Laktyushkin at amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng at amd.com>
Acked-by: Harry Wentland <harry.wentland at amd.com>
---
 drivers/gpu/drm/amd/display/dc/basics/fixpt31_32.c | 24 ++++++++++++++++++----
 .../gpu/drm/amd/display/dc/dcn10/dcn10_cm_common.c | 14 ++++++-------
 drivers/gpu/drm/amd/display/include/fixed31_32.h   |  4 ++--
 3 files changed, 29 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/basics/fixpt31_32.c b/drivers/gpu/drm/amd/display/dc/basics/fixpt31_32.c
index 13f8b8c02212..011a97f82fb6 100644
--- a/drivers/gpu/drm/amd/display/dc/basics/fixpt31_32.c
+++ b/drivers/gpu/drm/amd/display/dc/basics/fixpt31_32.c
@@ -554,6 +554,22 @@ static inline uint32_t ux_dy(
 	return result | fractional_part;
 }
 
+static inline uint32_t clamp_ux_dy(
+	int64_t value,
+	uint32_t integer_bits,
+	uint32_t fractional_bits,
+	uint32_t min_clamp)
+{
+	uint32_t truncated_val = ux_dy(value, integer_bits, fractional_bits);
+
+	if (value >= (1LL << (integer_bits + FIXED31_32_BITS_PER_FRACTIONAL_PART)))
+		return (1 << (integer_bits + fractional_bits)) - 1;
+	else if (truncated_val > min_clamp)
+		return truncated_val;
+	else
+		return min_clamp;
+}
+
 uint32_t dal_fixed31_32_u2d19(
 	struct fixed31_32 arg)
 {
@@ -566,14 +582,14 @@ uint32_t dal_fixed31_32_u0d19(
 	return ux_dy(arg.value, 0, 19);
 }
 
-uint32_t dal_fixed31_32_u0d14(
+uint32_t dal_fixed31_32_clamp_u0d14(
 	struct fixed31_32 arg)
 {
-	return ux_dy(arg.value, 1, 14);
+	return clamp_ux_dy(arg.value, 0, 14, 1);
 }
 
-uint32_t dal_fixed31_32_u0d10(
+uint32_t dal_fixed31_32_clamp_u0d10(
 	struct fixed31_32 arg)
 {
-	return ux_dy(arg.value, 1, 10);
+	return clamp_ux_dy(arg.value, 0, 10, 1);
 }
diff --git a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_cm_common.c b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_cm_common.c
index 352ae7bf9a3f..53ba3600ee6a 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_cm_common.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_cm_common.c
@@ -169,7 +169,7 @@ bool cm_helper_convert_to_custom_float(
 	}
 
 	if (fixpoint == true)
-		arr_points[1].custom_float_y = dal_fixed31_32_u0d14(arr_points[1].y);
+		arr_points[1].custom_float_y = dal_fixed31_32_clamp_u0d14(arr_points[1].y);
 	else if (!convert_to_custom_float_format(arr_points[1].y, &fmt,
 		&arr_points[1].custom_float_y)) {
 		BREAK_TO_DEBUGGER();
@@ -395,12 +395,12 @@ bool cm_helper_translate_curve_to_hw_format(
 		rgb->delta_blue  = dal_fixed31_32_sub(rgb_plus_1->blue,  rgb->blue);
 
 		if (fixpoint == true) {
-			rgb->delta_red_reg   = dal_fixed31_32_u0d10(rgb->delta_red);
-			rgb->delta_green_reg = dal_fixed31_32_u0d10(rgb->delta_green);
-			rgb->delta_blue_reg  = dal_fixed31_32_u0d10(rgb->delta_blue);
-			rgb->red_reg         = dal_fixed31_32_u0d14(rgb->red);
-			rgb->green_reg       = dal_fixed31_32_u0d14(rgb->green);
-			rgb->blue_reg        = dal_fixed31_32_u0d14(rgb->blue);
+			rgb->delta_red_reg   = dal_fixed31_32_clamp_u0d10(rgb->delta_red);
+			rgb->delta_green_reg = dal_fixed31_32_clamp_u0d10(rgb->delta_green);
+			rgb->delta_blue_reg  = dal_fixed31_32_clamp_u0d10(rgb->delta_blue);
+			rgb->red_reg         = dal_fixed31_32_clamp_u0d14(rgb->red);
+			rgb->green_reg       = dal_fixed31_32_clamp_u0d14(rgb->green);
+			rgb->blue_reg        = dal_fixed31_32_clamp_u0d14(rgb->blue);
 		}
 
 		++rgb_plus_1;
diff --git a/drivers/gpu/drm/amd/display/include/fixed31_32.h b/drivers/gpu/drm/amd/display/include/fixed31_32.h
index c4848fadc70e..4badaedbaadd 100644
--- a/drivers/gpu/drm/amd/display/include/fixed31_32.h
+++ b/drivers/gpu/drm/amd/display/include/fixed31_32.h
@@ -464,10 +464,10 @@ uint32_t dal_fixed31_32_u0d19(
 	struct fixed31_32 arg);
 
 
-uint32_t dal_fixed31_32_u0d14(
+uint32_t dal_fixed31_32_clamp_u0d14(
 	struct fixed31_32 arg);
 
-uint32_t dal_fixed31_32_u0d10(
+uint32_t dal_fixed31_32_clamp_u0d10(
 	struct fixed31_32 arg);
 
 #endif
-- 
2.14.1