linux-kernel - [PATCH 1/2] drm/amd/display: Optimize reserved time candidates sorting using standard sort()

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Message-Id: <20250824182359.142050-2-visitorckw@gmail.com>
Date: Mon, 25 Aug 2025 02:23:58 +0800
From: Kuan-Wei Chiu <visitorckw@...il.com>
To: austin.zheng@....com,
	jun.lei@....com,
	harry.wentland@....com,
	sunpeng.li@....com,
	siqueira@...lia.com,
	alexander.deucher@....com,
	christian.koenig@....com,
	airlied@...il.com,
	simona@...ll.ch
Cc: zaeem.mohamed@....com,
	wenjing.liu@....com,
	chiahsuan.chung@....com,
	Natanel.Roizenman@....com,
	Daniel.Sa@....com,
	jserv@...s.ncku.edu.tw,
	amd-gfx@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	Kuan-Wei Chiu <visitorckw@...il.com>
Subject: [PATCH 1/2] drm/amd/display: Optimize reserved time candidates sorting using standard sort()

Replace the custom bubble sort used for sorting reserved time
candidates in with the kernel's standard sort() helper. The previous
code had O(N^2) time complexity, while the generic kernel sort runs in
O(N log N). This improves efficiency and removes the need for a local
sorting implementation, while keeping functionality unchanged.

Signed-off-by: Kuan-Wei Chiu <visitorckw@...il.com>
---
Compile test only. 

 .../dml2/dml21/src/dml2_pmo/dml2_pmo_dcn3.c   | 23 +++++++++++--------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dml2/dml21/src/dml2_pmo/dml2_pmo_dcn3.c b/drivers/gpu/drm/amd/display/dc/dml2/dml21/src/dml2_pmo/dml2_pmo_dcn3.c
index e763c8e45da8..2b13a5e88917 100644
--- a/drivers/gpu/drm/amd/display/dc/dml2/dml21/src/dml2_pmo/dml2_pmo_dcn3.c
+++ b/drivers/gpu/drm/amd/display/dc/dml2/dml21/src/dml2_pmo/dml2_pmo_dcn3.c
@@ -2,19 +2,21 @@
 //
 // Copyright 2024 Advanced Micro Devices, Inc.
 
+#include <linux/sort.h>
+
 #include "dml2_pmo_factory.h"
 #include "dml2_pmo_dcn3.h"
 
-static void sort(double *list_a, int list_a_size)
+static int cmp_double(const void *a, const void *b)
 {
-	// For all elements b[i] in list_b[]
-	for (int i = 0; i < list_a_size - 1; i++) {
-		// Find the first element of list_a that's larger than b[i]
-		for (int j = i; j < list_a_size - 1; j++) {
-			if (list_a[j] > list_a[j + 1])
-				swap(list_a[j], list_a[j + 1]);
-		}
-	}
+	double da = *(const double *)a;
+	double db = *(const double *)b;
+
+	if (da < db)
+		return -1;
+	if (da > db)
+		return 1;
+	return 0;
 }
 
 static double get_max_reserved_time_on_all_planes_with_stream_index(struct display_configuation_with_meta *config, unsigned int stream_index)
@@ -634,7 +636,8 @@ bool pmo_dcn3_init_for_pstate_support(struct dml2_pmo_init_for_pstate_support_in
 
 		// Finally sort the array of candidates
 		sort(pmo->scratch.pmo_dcn3.reserved_time_candidates[stream_index],
-			pmo->scratch.pmo_dcn3.reserved_time_candidates_count[stream_index]);
+		     pmo->scratch.pmo_dcn3.reserved_time_candidates_count[stream_index],
+		     sizeof(double), cmp_double, NULL);
 
 		remove_duplicates(pmo->scratch.pmo_dcn3.reserved_time_candidates[stream_index],
 			&pmo->scratch.pmo_dcn3.reserved_time_candidates_count[stream_index]);
-- 
2.34.1