[PATCH 4.19 15/41] drm/amd/dm: Dont forget to attach MST encoders

Greg Kroah-Hartman
2018-12-06T14:40:09Z

From: Lyude Paul <lyude@redhat.com>

commit c9e0ab86b2e03154bb898cd2f851827783224727 upstream.

The change fixed huge delay in SST daisy chain and S3 soft hang
observed in 4.19 kernel rebase.

Regression point in drm:
drm/fb-helper: Eliminate the .best_encoder() usage

The aux sequence is altered due to the failure in
drm_connector_for_each_possible_encoder(). The failure is
caused by missing attached encoder in the process of adding
MST connector.

drm_dp_send_enum_path_resources() aux transaction is pushed after
mode probe, which causes conflict to drm_dp_mst_i2c_xfer(),
leading to the transaction timeout.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Jerry (Fangzhi) Zuo <Jerry.Zuo@amd.com>
Cc: Stable <stable@vger.kernel.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c | 2 ++
1 file changed, 2 insertions(+)

--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
@@ -374,6 +374,8 @@ dm_dp_add_mst_connector(struct drm_dp_ms
master->connector_id);

aconnector->mst_encoder = dm_dp_create_fake_mst_encoder(master);
+ drm_connector_attach_encoder(&aconnector->base,
+ &aconnector->mst_encoder->base);

/*
* TODO: understand why this one is needed