8b/10b encoding format requires to reserve the first slot for
recording metadata. Real data transmission starts from the second slot,
with a total of available 63 slots available.

In 128b/132b encoding format, metadata is transmitted separately
in LLCP packet before MTP. Real data transmission starts from
the first slot, with a total of 64 slots available.

Signed-off-by: Fangzhi Zuo <jerry....@amd.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 27 ++++++++++++++++++++-------
 include/drm/drm_dp_mst_helper.h       |  9 +++++++++
 2 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c 
b/drivers/gpu/drm/drm_dp_mst_topology.c
index 86d13d6bc463..30544801d2b8 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -3370,7 +3370,7 @@ int drm_dp_update_payload_part1(struct 
drm_dp_mst_topology_mgr *mgr)
        struct drm_dp_payload req_payload;
        struct drm_dp_mst_port *port;
        int i, j;
-       int cur_slots = 1;
+       int cur_slots = mgr->start_slot;
        bool skip;
 
        mutex_lock(&mgr->payload_lock);
@@ -4323,7 +4323,7 @@ int drm_dp_find_vcpi_slots(struct drm_dp_mst_topology_mgr 
*mgr,
        num_slots = DIV_ROUND_UP(pbn, mgr->pbn_div);
 
        /* max. time slots - one slot for MTP header */
-       if (num_slots > 63)
+       if (num_slots > mgr->total_avail_slots)
                return -ENOSPC;
        return num_slots;
 }
@@ -4335,7 +4335,7 @@ static int drm_dp_init_vcpi(struct 
drm_dp_mst_topology_mgr *mgr,
        int ret;
 
        /* max. time slots - one slot for MTP header */
-       if (slots > 63)
+       if (slots > mgr->total_avail_slots)
                return -ENOSPC;
 
        vcpi->pbn = pbn;
@@ -4509,6 +4509,17 @@ int drm_dp_atomic_release_vcpi_slots(struct 
drm_atomic_state *state,
 }
 EXPORT_SYMBOL(drm_dp_atomic_release_vcpi_slots);
 
+void drm_dp_mst_update_encoding_cap(struct drm_dp_mst_topology_mgr *mgr, 
uint8_t link_encoding_cap)
+{
+       if (link_encoding_cap == DP_CAP_ANSI_128B132B) {
+               mgr->total_avail_slots = 64;
+               mgr->start_slot = 0;
+       }
+       DRM_DEBUG_KMS("%s encoding format determined\n",
+                     (link_encoding_cap == DP_CAP_ANSI_128B132B) ? "128b/132b" 
: "8b/10b");
+}
+EXPORT_SYMBOL(drm_dp_mst_update_encoding_cap);
+
 /**
  * drm_dp_mst_allocate_vcpi() - Allocate a virtual channel
  * @mgr: manager for this port
@@ -4540,8 +4551,8 @@ bool drm_dp_mst_allocate_vcpi(struct 
drm_dp_mst_topology_mgr *mgr,
 
        ret = drm_dp_init_vcpi(mgr, &port->vcpi, pbn, slots);
        if (ret) {
-               drm_dbg_kms(mgr->dev, "failed to init vcpi slots=%d max=63 
ret=%d\n",
-                           DIV_ROUND_UP(pbn, mgr->pbn_div), ret);
+               drm_dbg_kms(mgr->dev, "failed to init vcpi slots=%d max=%d 
ret=%d\n",
+                           DIV_ROUND_UP(pbn, mgr->pbn_div), 
mgr->total_avail_slots, ret);
                drm_dp_mst_topology_put_port(port);
                goto out;
        }
@@ -5228,7 +5239,7 @@ drm_dp_mst_atomic_check_vcpi_alloc_limit(struct 
drm_dp_mst_topology_mgr *mgr,
                                         struct drm_dp_mst_topology_state 
*mst_state)
 {
        struct drm_dp_vcpi_allocation *vcpi;
-       int avail_slots = 63, payload_count = 0;
+       int avail_slots = mgr->total_avail_slots, payload_count = 0;
 
        list_for_each_entry(vcpi, &mst_state->vcpis, next) {
                /* Releasing VCPI is always OK-even if the port is gone */
@@ -5257,7 +5268,7 @@ drm_dp_mst_atomic_check_vcpi_alloc_limit(struct 
drm_dp_mst_topology_mgr *mgr,
                }
        }
        drm_dbg_atomic(mgr->dev, "[MST MGR:%p] mst state %p VCPI avail=%d 
used=%d\n",
-                      mgr, mst_state, avail_slots, 63 - avail_slots);
+                      mgr, mst_state, avail_slots, mgr->total_avail_slots - 
avail_slots);
 
        return 0;
 }
@@ -5529,6 +5540,8 @@ int drm_dp_mst_topology_mgr_init(struct 
drm_dp_mst_topology_mgr *mgr,
        if (!mgr->proposed_vcpis)
                return -ENOMEM;
        set_bit(0, &mgr->payload_mask);
+       mgr->total_avail_slots = 63;
+       mgr->start_slot = 1;
 
        mst_state = kzalloc(sizeof(*mst_state), GFP_KERNEL);
        if (mst_state == NULL)
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index ddb9231d0309..eac5ce48f214 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -661,6 +661,15 @@ struct drm_dp_mst_topology_mgr {
         */
        int pbn_div;
 
+       /**
+        * @total_avail_slots: available slots for data transmission
+        */
+       u8 total_avail_slots;
+       /**
+        * @start_slot: first slot index for data transmission
+        */
+       u8 start_slot;
+
        /**
         * @funcs: Atomic helper callbacks
         */
-- 
2.25.1

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