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 5b7ad38f85e08f422c32e48bdb4b384b8bb75e08..65e45a0b4ff34351013a6e7f5debe0eb8c676e8d 100644 (file)
--- 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,