Commit 9070d18f authored by Aric Cyr's avatar Aric Cyr Committed by Alex Deucher
Browse files

drm/amd/display: Add a hysteresis to BTR frame multiplier 



[Why]
Flickering is observed on some displays when the number of inserted BTR
frames changes frequently.

[How]
Add in a margin of drift to prevent the inserted number of frames from
jumping around too frequently.

Signed-off-by: default avatarAric Cyr <aric.cyr@amd.com>
Reviewed-by: default avatarNicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Acked-by: default avatarBhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent 7fe538a4

drivers/gpu/drm/amd/display/modules/freesync/freesync.c

+22 −2
Original line number Diff line number Diff line
@@ -37,6 +37,8 @@ 
#define RENDER_TIMES_MAX_COUNT 10

/* Threshold to exit BTR (to avoid frequent enter-exits at the lower limit) */

#define BTR_EXIT_MARGIN 2000

/* Threshold to change BTR multiplier (to avoid frequent changes) */

#define BTR_DRIFT_MARGIN 2000

/*Threshold to exit fixed refresh rate*/

#define FIXED_REFRESH_EXIT_MARGIN_IN_HZ 4

/* Number of consecutive frames to check before entering/exiting fixed refresh*/
@@ -248,6 +250,7 @@ static void apply_below_the_range(struct core_freesync *core_freesync, 
	unsigned int frames_to_insert = 0;

	unsigned int min_frame_duration_in_ns = 0;

	unsigned int max_render_time_in_us = in_out_vrr->max_duration_in_us;

	unsigned int delta_from_mid_point_delta_in_us;



	min_frame_duration_in_ns = ((unsigned int) (div64_u64(

		(1000000000ULL * 1000000),
@@ -318,10 +321,27 @@ static void apply_below_the_range(struct core_freesync *core_freesync, 
		/* Choose number of frames to insert based on how close it

		 * can get to the mid point of the variable range.

		 */

		if (delta_from_mid_point_in_us_1 < delta_from_mid_point_in_us_2)

		if (delta_from_mid_point_in_us_1 < delta_from_mid_point_in_us_2) {

			frames_to_insert = mid_point_frames_ceil;

		else

			delta_from_mid_point_delta_in_us = delta_from_mid_point_in_us_2 -

					delta_from_mid_point_in_us_1;

		} else {

			frames_to_insert = mid_point_frames_floor;

			delta_from_mid_point_delta_in_us = delta_from_mid_point_in_us_1 -

					delta_from_mid_point_in_us_2;

		}



		/* Prefer current frame multiplier when BTR is enabled unless it drifts

		 * too far from the midpoint

		 */

		if (in_out_vrr->btr.frames_to_insert != 0 &&

				delta_from_mid_point_delta_in_us < BTR_DRIFT_MARGIN) {

			if (((last_render_time_in_us / in_out_vrr->btr.frames_to_insert) <

					in_out_vrr->max_duration_in_us) &&

				((last_render_time_in_us / in_out_vrr->btr.frames_to_insert) >

					in_out_vrr->min_duration_in_us))

				frames_to_insert = in_out_vrr->btr.frames_to_insert;

		}



		/* Either we've calculated the number of frames to insert,

		 * or we need to insert min duration frames

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