[PATCH 06/37] drm/amd/display: Handle Y carry-over in VCP X.Y calculation

[Aurabindo Pillai]

From: George Shen <george.shen at amd.com>

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 at vger.kernel.org
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira at amd.com>
Signed-off-by: George Shen <george.shen at amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler at amd.com>
---
 .../drm/amd/display/dc/dcn31/dcn31_hpo_dp_link_encoder.c    | 6 ++++++
 1 file changed, 6 insertions(+)

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 48e63550f696..03b4ac2f1991 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,
-- 
2.44.0