From: David Francis <david.fran...@amd.com>

As of DP1.4, ENUM_PATH_RESOURCES returns a bit indicating
if FEC can be supported up to that point in the MST network.

The bit is the first byte of the ENUM_PATH_RESOURCES ack reply,
bottom-most bit (refer to section 2.11.9.4 of DP standard,
v1.4)

That value is needed for FEC and DSC support

Store it on drm_dp_mst_port

Reviewed-by: Lyude Paul <ly...@redhat.com>
Reviewed-by: Harry Wentland <harry.wentl...@amd.com>
Signed-off-by: David Francis <david.fran...@amd.com>
Signed-off-by: Mikita Lipski <mikita.lip...@amd.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 2 ++
 include/drm/drm_dp_mst_helper.h       | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c 
b/drivers/gpu/drm/drm_dp_mst_topology.c
index 261e2c1828c6..06aae9b52e8a 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -846,6 +846,7 @@ static bool 
drm_dp_sideband_parse_enum_path_resources_ack(struct drm_dp_sideband
 {
        int idx = 1;
        repmsg->u.path_resources.port_number = (raw->msg[idx] >> 4) & 0xf;
+       repmsg->u.path_resources.fec_capable = raw->msg[idx] & 0x1;
        idx++;
        if (idx > raw->curlen)
                goto fail_len;
@@ -2894,6 +2895,7 @@ drm_dp_send_enum_path_resources(struct 
drm_dp_mst_topology_mgr *mgr,
                                      path_res->avail_payload_bw_number);
                        port->available_pbn =
                                path_res->avail_payload_bw_number;
+                       port->fec_capable = path_res->fec_capable;
                }
        }
 
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 68656913cfe5..0cada01e8139 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -156,6 +156,8 @@ struct drm_dp_mst_port {
         * audio-capable.
         */
        bool has_audio;
+
+       bool fec_capable;
 };
 
 /**
@@ -383,6 +385,7 @@ struct drm_dp_port_number_req {
 
 struct drm_dp_enum_path_resources_ack_reply {
        u8 port_number;
+       bool fec_capable;
        u16 full_payload_bw_number;
        u16 avail_payload_bw_number;
 };
-- 
2.17.1

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