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drm/dp_mst: Use Extended Base Receiver Capability DPCD space

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[why]
DP 1.4a spec mandates that if DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT is
set, Extended Base Receiver Capability DPCD space must be used. Without
doing that, the three DPCD values that differ will be wrong, leading to
incorrect or limited functionality. MST link rate, for example, could
have a lower value. Also, Synaptics quirk wouldn't work out well when
Extended DPCD was not read, resulting in no DSC for such hubs.

[how]
Modify MST topology manager to use the values from Extended DPCD where
applicable.

To prevent regression on the sources that have a lower maximum link rate
capability than MAX_LINK_RATE from Extended DPCD, have the drivers
supply maximum lane count and rate at initialization time.

This also reverts commit 2dcab875e7 ("Revert drm/dp_mst: Retrieve
extended DPCD caps for topology manager"), brining the change back to the
original commit ad44c03208 ("drm/dp_mst: Retrieve extended DPCD caps for
topology manager").

Signed-off-by: Nikola Cornij <nikola.cornij@amd.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210429221151.22020-2-nikola.cornij@amd.com
This commit is contained in:
Nikola Cornij
2021-04-29 18:11:51 -04:00
committed by Lyude Paul
parent 310e506c06
commit 98025a62cb
8 changed files with 71 additions and 15 deletions
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5
drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
View File

@@ -429,6 +429,8 @@ void amdgpu_dm_initialize_dp_connector(struct amdgpu_display_manager *dm,
struct amdgpu_dm_connector *aconnector,
int link_index)
{
struct dc_link_settings max_link_enc_cap = {0};
aconnector->dm_dp_aux.aux.name =
kasprintf(GFP_KERNEL, "AMDGPU DM aux hw bus %d",
link_index);
@@ -443,6 +445,7 @@ void amdgpu_dm_initialize_dp_connector(struct amdgpu_display_manager *dm,
if (aconnector->base.connector_type == DRM_MODE_CONNECTOR_eDP)
return;
dc_link_dp_get_max_link_enc_cap(aconnector->dc_link, &max_link_enc_cap);
aconnector->mst_mgr.cbs = &dm_mst_cbs;
drm_dp_mst_topology_mgr_init(
&aconnector->mst_mgr,
@@ -450,6 +453,8 @@ void amdgpu_dm_initialize_dp_connector(struct amdgpu_display_manager *dm,
&aconnector->dm_dp_aux.aux,
16,
4,
(u8)max_link_enc_cap.lane_count,
(u8)max_link_enc_cap.link_rate,
aconnector->connector_id);
drm_connector_attach_dp_subconnector_property(&aconnector->base);