Currently, DRM get the capability of the mst hub only from DP_DPCD_REV and
get the slower speed even the mst hub can run in the faster speed.
As per DP-1.3, First check DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT.
If DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT is 1, read the DP_DP13_DPCD_REV to
get the faster capability.
If DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT is 0, read DP_DPCD_REV.
Signed-off-by: Koba Ko <koba.ko@xxxxxxxxxxxxx>
---
drivers/gpu/drm/drm_dp_mst_topology.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 67dd72ea200e..3b84c6801281 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -3497,6 +3497,8 @@ static int drm_dp_get_vc_payload_bw(u8 dp_link_bw, u8 dp_link_count)
int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool mst_state)
{
int ret = 0;
+ u8 dpcd_ext = 0;
+ unsigned int dpcd_offset = 0;
struct drm_dp_mst_branch *mstb = NULL;
mutex_lock(&mgr->payload_lock);
@@ -3510,9 +3512,15 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms
struct drm_dp_payload reset_pay;
WARN_ON(mgr->mst_primary);
+ drm_dp_dpcd_read(mgr->aux,
+ DP_TRAINING_AUX_RD_INTERVAL,
+ &dpcd_ext, sizeof(dpcd_ext));
+
+ dpcd_offset =
+ ((dpcd_ext & DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT) ? DP_DP13_DPCD_REV : DP_DPCD_REV);
/* get dpcd info */
- ret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, mgr->dpcd, DP_RECEIVER_CAP_SIZE);
+ ret = drm_dp_dpcd_read(mgr->aux, dpcd_offset, mgr->dpcd, DP_RECEIVER_CAP_SIZE);
if (ret != DP_RECEIVER_CAP_SIZE) {
DRM_DEBUG_KMS("failed to read DPCD\n");
goto out_unlock;
--
2.25.1
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