[PATCH 5.15 61/73] drm/amd/display: Fix pixel clock programming

[Greg Kroah-Hartman]

From: Ilya Bakoulin <Ilya.Bakoulin@xxxxxxx>

[ Upstream commit 04fb918bf421b299feaee1006e82921d7d381f18 ]

[Why]
Some pixel clock values could cause HDMI TMDS SSCPs to be misaligned
between different HDMI lanes when using YCbCr420 10-bit pixel format.

BIOS functions for transmitter/encoder control take pixel clock in kHz
increments, whereas the function for setting the pixel clock is in 100Hz
increments. Setting pixel clock to a value that is not on a kHz boundary
will cause the issue.

[How]
Round pixel clock down to nearest kHz in 10/12-bpc cases.

Reviewed-by: Aric Cyr <Aric.Cyr@xxxxxxx>
Acked-by: Brian Chang <Brian.Chang@xxxxxxx>
Signed-off-by: Ilya Bakoulin <Ilya.Bakoulin@xxxxxxx>
Tested-by: Daniel Wheeler <daniel.wheeler@xxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c b/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c
index 054823d12403d..5f1b735da5063 100644
--- a/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c
+++ b/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c
@@ -545,9 +545,11 @@ static void dce112_get_pix_clk_dividers_helper (
 		switch (pix_clk_params->color_depth) {
 		case COLOR_DEPTH_101010:
 			actual_pixel_clock_100hz = (actual_pixel_clock_100hz * 5) >> 2;
+			actual_pixel_clock_100hz -= actual_pixel_clock_100hz % 10;
 			break;
 		case COLOR_DEPTH_121212:
 			actual_pixel_clock_100hz = (actual_pixel_clock_100hz * 6) >> 2;
+			actual_pixel_clock_100hz -= actual_pixel_clock_100hz % 10;
 			break;
 		case COLOR_DEPTH_161616:
 			actual_pixel_clock_100hz = actual_pixel_clock_100hz * 2;
-- 
2.35.1