drm/amd/display: Force DSC to 8bpp for SST DP tunneling over USB4

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A 4K144 display attached through a USB4 (Thunderbolt) dock does not light
up on DCN4.2.  The native DP link bandwidth reported for the sink is far
larger than the USB4 tunnel can carry, so DSC is sized to the link and the
resulting stream overflows the tunnel's granted bandwidth.  The bandwidth
allocation request fails and the display stays dark.

When the endpoint is a USB4 DPIA with BW allocation enabled, force DSC and
cap the target to 8 bpp in SST mode. This keeps the compressed stream within
the tunnel budget and reserves headroom for other DP tunnels
sharing the same host router.

Reviewed-by: Roman Li <roman.li@amd.com>
Signed-off-by: Fangzhi Zuo <jerry.zuo@amd.com>
Signed-off-by: Chenyu Chen <chen-yu.chen@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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Fangzhi Zuo 2026-09-01 15:32:30 -04:00 • committed by Alex Deucher

parent cd53dcd2a7

commit c30b9813bc

1 changed files with 6 additions and 0 deletions

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drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.c

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