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

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Message-Id: <20181206142951.034168427@linuxfoundation.org>
Date:   Thu,  6 Dec 2018 15:38:55 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Lyude Paul <lyude@...hat.com>,
        "Jerry (Fangzhi) Zuo" <Jerry.Zuo@....com>,
        Alex Deucher <alexander.deucher@....com>
Subject: [PATCH 4.19 15/41] drm/amd/dm: Dont forget to attach MST encoders

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

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