From: Victor Lu <victorchengchi.lu@amd.com>
Date: Thu, 8 Jul 2021 18:50:48 +0000 (-0400)
Subject: drm/amd/display: Guard DST_Y_PREFETCH register overflow in DCN21
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=c8f8e96805b54968b4d1d54850f87fc39128a532;p=linux.git

drm/amd/display: Guard DST_Y_PREFETCH register overflow in DCN21

[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@amd.com>
Acked-by: Solomon Chiu <solomon.chiu@amd.com>
Signed-off-by: Victor Lu <victorchengchi.lu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
---

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 d25a7d38d21fe..6655bb99fdfd0 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);