drm/amd/display: Notify DMU to allow DCHVM<->rIOMMU SDP port disconnection for DCN42

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[why & how]
Allowing the DCHVM<->rIOMMU SDP port to disconnect during IPS1 cycling
can cause extra credits
to be released to rIOMMU. In turn, this will let the rIOMMU issue more
outstanding table walk requests
at once, overflowing the downstream request FIFO. This results in
dropped/orphaned
requests with no method of recovery. This typically manifests as an
invalidation hang error
in the main IOMMU.

As a workaround, dis-allow the SDP port from disconnecting from IPS1 exit
up until after
powerstatus=1. This ensures that rIOMMU does not have the chance to request
credits multiple
times during the powerstatus 0->1 transition.

Since x86 driver cannot access rIOMMU register space, send a command to DMU
to do it.

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Ovidiu Bunea <ovidiu.bunea@amd.com>
Signed-off-by: James Lin <pinglei.lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

...

This commit is contained in:

Ovidiu Bunea 2026-08-04 16:06:34 -04:00 • committed by Alex Deucher

parent ee14b1dc90

commit 322a0695ac

3 changed files with 37 additions and 0 deletions

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18

drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c

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12

drivers/gpu/drm/amd/display/dc/dc_dmub_srv.h

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7

drivers/gpu/drm/amd/display/dc/hubbub/dcn35/dcn35_hubbub.c

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