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

[Kuan-Wei Chiu]

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 at gmail.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