Merge tag 'drm-intel-next-2021-01-29' of git://anongit.freedesktop.org/drm/drm-intel...

[linux.git] / drivers / gpu / drm / drm_dp_mst_topology.c

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 475939138b212b04f072557c9cec51040280dfb2..e82b596d646c24e4ac0a94cf44e8add73fa72d51 100644 (file)
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -3629,14 +3629,26 @@ static int drm_dp_send_up_ack_reply(struct drm_dp_mst_topology_mgr *mgr,
        return 0;
 }
 
-static int drm_dp_get_vc_payload_bw(u8 dp_link_bw, u8  dp_link_count)
+/**
+ * drm_dp_get_vc_payload_bw - get the VC payload BW for an MST link
+ * @link_rate: link rate in 10kbits/s units
+ * @link_lane_count: lane count
+ *
+ * Calculate the total bandwidth of a MultiStream Transport link. The returned
+ * value is in units of PBNs/(timeslots/1 MTP). This value can be used to
+ * convert the number of PBNs required for a given stream to the number of
+ * timeslots this stream requires in each MTP.
+ */
+int drm_dp_get_vc_payload_bw(int link_rate, int link_lane_count)
 {
-       if (dp_link_bw == 0 || dp_link_count == 0)
-               DRM_DEBUG_KMS("invalid link bandwidth in DPCD: %x (link count: %d)\n",
-                             dp_link_bw, dp_link_count);
+       if (link_rate == 0 || link_lane_count == 0)
+               DRM_DEBUG_KMS("invalid link rate/lane count: (%d / %d)\n",
+                             link_rate, link_lane_count);
 
-       return dp_link_bw * dp_link_count / 2;
+       /* See DP v2.0 2.6.4.2, VCPayload_Bandwidth_for_OneTimeSlotPer_MTP_Allocation */
+       return link_rate * link_lane_count / 54000;
 }
+EXPORT_SYMBOL(drm_dp_get_vc_payload_bw);
 
 /**
  * drm_dp_read_mst_cap() - check whether or not a sink supports MST
@@ -3692,7 +3704,7 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms
                        goto out_unlock;
                }
 
-               mgr->pbn_div = drm_dp_get_vc_payload_bw(mgr->dpcd[1],
+               mgr->pbn_div = drm_dp_get_vc_payload_bw(drm_dp_bw_code_to_link_rate(mgr->dpcd[1]),
                                                        mgr->dpcd[2] & DP_MAX_LANE_COUNT_MASK);
                if (mgr->pbn_div == 0) {
                        ret = -EINVAL;