drm/amd/display: only reprogram DRR when v_total values change

[Why]
dc_stream_adjust_vmin_vmax() programmed the OTG on every call. FreeSync
BTR calls it once per vblank, so identical v_total values were rewritten
every frame, each one paying dc_exit_ips_for_hw_access() and, when FAMS
is enabled, a blocking DMUB round trip from setup_manual_trigger().

[How]
Return early when timing_adjust_pending is clear and every v_total field
already matches the request, so hardware is only touched when the values
change. stream->adjust is still updated on every path that continues, so
a later commit programs the requested values.

timing_adjust_pending is the existing "stream->adjust has not reached
hardware" marker, so keep it accurate wherever hardware is left
untouched: set_drr_and_clear_adjust_pending() now sets it when called
with null params, which resets DRR in the OTG during pipe back-end
teardown, and the max_v_total overflow path only clears it when
set_long_vtotal() runs.

Reviewed-by: Josip Pavic <josip.pavic@amd.com>
Signed-off-by: Aric Cyr <Aric.Cyr@amd.com>
Signed-off-by: Roman Li <roman.li@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

2 files changed, 22 insertions, 5 deletions

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc.c b/drivers/gpu/drm/amd/display/dc/core/dc.c
index 878856ee1dfe..4e3f04530013 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc.c
@@ -1341,6 +1341,7 @@ bool dc_stream_adjust_vmin_vmax(struct dc *dc,
 		struct dc_crtc_timing_adjust *adjust)
 {
 	int i;
+	bool drr_unchanged;
 
 	/*
 	 * Don't adjust DRR while there's bandwidth optimizations pending to
@@ -1355,6 +1356,19 @@ bool dc_stream_adjust_vmin_vmax(struct dc *dc,
 		}
 	}
 
+	/* timing_adjust_pending tracks whether stream->adjust still describes the
+	 * OTG, so a cleared flag plus matching values means hw is already current.
+	 */
+	drr_unchanged = !stream->adjust.timing_adjust_pending &&
+			stream->adjust.v_total_min == adjust->v_total_min &&
+			stream->adjust.v_total_max == adjust->v_total_max &&
+			stream->adjust.v_total_mid == adjust->v_total_mid &&
+			stream->adjust.v_total_mid_frame_num == adjust->v_total_mid_frame_num &&
+			stream->adjust.allow_otg_v_count_halt == adjust->allow_otg_v_count_halt;
+
+	if (drr_unchanged)
+		return true;
+
 	dc_exit_ips_for_hw_access(dc);
 
 	stream->adjust.v_total_max = adjust->v_total_max;
@@ -1365,11 +1379,13 @@ bool dc_stream_adjust_vmin_vmax(struct dc *dc,
 
 	if (dc->caps.max_v_total != 0 &&
 		(adjust->v_total_max > dc->caps.max_v_total || adjust->v_total_min > dc->caps.max_v_total)) {
-		stream->adjust.timing_adjust_pending = false;
-		if (adjust->allow_otg_v_count_halt)
+		if (adjust->allow_otg_v_count_halt) {
+			stream->adjust.timing_adjust_pending = false;
 			return set_long_vtotal(dc, stream, adjust);
-		else
-			return false;
+		}
+		/* Nothing reached hw, so stream->adjust no longer describes the OTG. */
+		stream->adjust.timing_adjust_pending = true;
+		return false;
 	}
 
 	for (i = 0; i < MAX_PIPES; i++) {
diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_hw_sequencer.c b/drivers/gpu/drm/amd/display/dc/core/dc_hw_sequencer.c
index 21a62ca4c8dc..3d88c5c377fc 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_hw_sequencer.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_hw_sequencer.c
@@ -716,7 +716,8 @@ void set_drr_and_clear_adjust_pending(
 				pipe_ctx->stream_res.tg, params);
 
 	if (stream)
-		stream->adjust.timing_adjust_pending = false;
+		/* A null params resets DRR in hw, leaving stream->adjust stale. */
+		stream->adjust.timing_adjust_pending = (params == NULL);
 }
 
 void get_fams2_visual_confirm_color(