[PATCH 16/20] drm/amd/display: Reduce I2C speed to 95kHz in DCN401

Alex Hung alex.hung at amd.com
Wed May 8 17:13:16 UTC 2024


From: Chris Park <chris.park at amd.com>

[WHY]
HW for DCN401 is presented with a small I2C speed fluctuation that
exceeds the hard cap limitation of 100kHz occasionally. This violates
compliance requirement and will result in failure in compliance.

[HOW]
After various measurements and traceback to previous generation HW, DCN IP,
SI and SW driver agrees that we can reduce I2C speed to 95kHz to address
the I2C spped fluctuation in DCN401.

Reviewed-by: Dillon Varone <dillon.varone at amd.com>
Acked-by: Alex Hung <alex.hung at amd.com>
Signed-off-by: Chris Park <chris.park at amd.com>
---
 .../gpu/drm/amd/display/dc/resource/dcn401/dcn401_resource.c  | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/resource/dcn401/dcn401_resource.c b/drivers/gpu/drm/amd/display/dc/resource/dcn401/dcn401_resource.c
index 75e2c62ae792..a55421363772 100644
--- a/drivers/gpu/drm/amd/display/dc/resource/dcn401/dcn401_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/resource/dcn401/dcn401_resource.c
@@ -1772,8 +1772,8 @@ static bool dcn401_resource_construct(
 	pool->base.pipe_count = num_pipes;
 	pool->base.mpcc_count = num_pipes;
 	dc->caps.max_downscale_ratio = 600;
-	dc->caps.i2c_speed_in_khz = 100;
-	dc->caps.i2c_speed_in_khz_hdcp = 100; /*1.4 w/a applied by default*/
+	dc->caps.i2c_speed_in_khz = 95;
+	dc->caps.i2c_speed_in_khz_hdcp = 95; /*1.4 w/a applied by default*/
 	/* TODO: Bring max cursor size back to 256 after subvp cursor corruption is fixed*/
 	dc->caps.max_cursor_size = 64;
 	dc->caps.cursor_not_scaled = true;
-- 
2.34.1



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