From: George Shen <george.shen@amd.com>
Date: Thu, 16 Sep 2021 23:55:39 +0000 (-0400)
Subject: drm/amd/display: Handle Y carry-over in VCP X.Y calculation
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=b528cac6deaacd7baa0896b7cb2cf98e87926d17;p=linux.git

drm/amd/display: Handle Y carry-over in VCP X.Y calculation

Theoretically rare corner case where ceil(Y) results in rounding up to
an integer. If this happens, the 1 should be carried over to the X
value.

CC: stable@vger.kernel.org
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: George Shen <george.shen@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/dcn31/dcn31_hpo_dp_link_encoder.c b/drivers/gpu/drm/amd/display/dc/dcn31/dcn31_hpo_dp_link_encoder.c
index 48e63550f696a..03b4ac2f1991a 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn31/dcn31_hpo_dp_link_encoder.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn31/dcn31_hpo_dp_link_encoder.c
@@ -395,6 +395,12 @@ void dcn31_hpo_dp_link_enc_set_throttled_vcp_size(
 				x),
 			25));
 
+	// If y rounds up to integer, carry it over to x.
+	if (y >> 25) {
+		x += 1;
+		y = 0;
+	}
+
 	switch (stream_encoder_inst) {
 	case 0:
 		REG_SET_2(DP_DPHY_SYM32_VC_RATE_CNTL0, 0,