[PATCH 01/14] drm/amd/display: Guard DST_Y_PREFETCH register overflow in DCN21

[Solomon Chiu]

From: Victor Lu <victorchengchi.lu at amd.com>

[why]
DST_Y_PREFETCH can overflow when DestinationLinesForPrefetch values are
too large due to the former being limited to 8 bits.

[how]
Set the maximum value of DestinationLinesForPrefetch to be 255 * refclk
period.

Reviewed-by: Laktyushkin Dmytro <dmytro.laktyushkin at amd.com>
Acked-by: Solomon Chiu <solomon.chiu at amd.com>
Signed-off-by: Victor Lu <victorchengchi.lu at amd.com>
---
 drivers/gpu/drm/amd/display/dc/dml/dcn21/display_mode_vba_21.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/dml/dcn21/display_mode_vba_21.c b/drivers/gpu/drm/amd/display/dc/dml/dcn21/display_mode_vba_21.c
index 506797c721ed..4136eb8256cb 100644
--- a/drivers/gpu/drm/amd/display/dc/dml/dcn21/display_mode_vba_21.c
+++ b/drivers/gpu/drm/amd/display/dc/dml/dcn21/display_mode_vba_21.c
@@ -841,6 +841,9 @@ static bool CalculatePrefetchSchedule(
 	else
 		*DestinationLinesForPrefetch = dst_y_prefetch_equ;
 
+	// Limit to prevent overflow in DST_Y_PREFETCH register
+	*DestinationLinesForPrefetch = dml_min(*DestinationLinesForPrefetch, 63.75);
+
 	dml_print("DML: VStartup: %d\n", VStartup);
 	dml_print("DML: TCalc: %f\n", TCalc);
 	dml_print("DML: TWait: %f\n", TWait);
-- 
2.25.1