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Subject[PATCH v3] drm/dp_mst: Retrieve extended DPCD caps for topology manager
Date
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@canonical.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
---
Changelog:
1. Adjust the commit message.
2. use drm_dbg_kms instead and print the return code.
---
drivers/gpu/drm/drm_dp_mst_topology.c | 14 +++-----------
1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 7753c718ddf9..63f8809b9aa4 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -3671,8 +3671,6 @@ EXPORT_SYMBOL(drm_dp_read_mst_cap);
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);
@@ -3686,17 +3684,11 @@ 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, dpcd_offset, mgr->dpcd, DP_RECEIVER_CAP_SIZE);
- if (ret != DP_RECEIVER_CAP_SIZE) {
- DRM_DEBUG_KMS("failed to read DPCD\n");
+ ret = drm_dp_read_dpcd_caps(mgr->aux, mgr->dpcd);
+ if (ret < 0) {
+ drm_dbg_kms(mgr->dev, "failed to read DPCD, ret %d\n", ret);
goto out_unlock;
}

--
2.25.1
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