drm: Update MST First Link Slot Information Based on Encoding Format

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.

v2:
* Move total/start slots to mst_state, and copy it to mst_mgr in
atomic_check

v3:
* Only keep the slot info on the mst_state
* add a start_slot parameter to the payload function, to facilitate non
  atomic drivers (this is a temporary workaround and should be removed when
  we are moving out the non atomic driver helpers)

v4:
*fixed typo and formatting

v5: (no functional changes)
* Fixed formatting in drm_dp_mst_update_slots()
* Reference mst_state instead of mst_state->mgr for debugging info
Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Fangzhi Zuo <Jerry.Zuo@amd.com>
[v5 nitpicks]
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211025223825.301703-3-lyude@redhat.com

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c

@@ -251,7 +251,7 @@ bool dm_helpers_dp_mst_write_payload_allocation_table(
 	}
 
 	/* It's OK for this to fail */
-	drm_dp_update_payload_part1(mst_mgr);
+	drm_dp_update_payload_part1(mst_mgr, 1);
 
 	/* mst_mgr->->payloads are VC payload notify MST branch using DPCD or
 	 * AUX message. The sequence is slot 1-63 allocated sequence for each

drivers/gpu/drm/drm_dp_mst_topology.c

@@ -3355,6 +3355,10 @@ static int drm_dp_destroy_payload_step2(struct drm_dp_mst_topology_mgr *mgr,
 /**
  * drm_dp_update_payload_part1() - Execute payload update part 1
  * @mgr: manager to use.
+ * @start_slot: this is the cur slot
+ *
+ * NOTE: start_slot is a temporary workaround for non-atomic drivers,
+ * this will be removed when non-atomic mst helpers are moved out of the helper
  *
  * This iterates over all proposed virtual channels, and tries to
  * allocate space in the link for them. For 0->slots transitions,
@@ -3365,12 +3369,12 @@ static int drm_dp_destroy_payload_step2(struct drm_dp_mst_topology_mgr *mgr,
  * after calling this the driver should generate ACT and payload
  * packets.
  */
-int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr)
+int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr, int start_slot)
 {
 	struct drm_dp_payload req_payload;
 	struct drm_dp_mst_port *port;
 	int i, j;
-	int cur_slots = 1;
+	int cur_slots = start_slot;
 	bool skip;
 
 	mutex_lock(&mgr->payload_lock);
@@ -4505,6 +4509,27 @@ int drm_dp_atomic_release_vcpi_slots(struct drm_atomic_state *state,
 }
 EXPORT_SYMBOL(drm_dp_atomic_release_vcpi_slots);
 
+/**
+ * drm_dp_mst_update_slots() - updates the slot info depending on the DP ecoding format
+ * @mst_state: mst_state to update
+ * @link_encoding_cap: the ecoding format on the link
+ */
+void drm_dp_mst_update_slots(struct drm_dp_mst_topology_state *mst_state, uint8_t link_encoding_cap)
+{
+	if (link_encoding_cap == DP_CAP_ANSI_128B132B) {
+		mst_state->total_avail_slots = 64;
+		mst_state->start_slot = 0;
+	} else {
+		mst_state->total_avail_slots = 63;
+		mst_state->start_slot = 1;
+	}
+
+	DRM_DEBUG_KMS("%s encoding format on mst_state 0x%p\n",
+		      (link_encoding_cap == DP_CAP_ANSI_128B132B) ? "128b/132b":"8b/10b",
+		      mst_state);
+}
+EXPORT_SYMBOL(drm_dp_mst_update_slots);
+
 /**
  * drm_dp_mst_allocate_vcpi() - Allocate a virtual channel
  * @mgr: manager for this port
@@ -5224,7 +5249,7 @@ 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 = mst_state->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 */
@@ -5253,7 +5278,7 @@ 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, mst_state->total_avail_slots - avail_slots);
 
 	return 0;
 }
@@ -5530,6 +5555,9 @@ int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr,
 	if (mst_state == NULL)
 		return -ENOMEM;
 
+	mst_state->total_avail_slots = 63;
+	mst_state->start_slot = 1;
+
 	mst_state->mgr = mgr;
 	INIT_LIST_HEAD(&mst_state->vcpis);
 

drivers/gpu/drm/i915/display/intel_dp_mst.c

@@ -378,7 +378,7 @@ static void intel_mst_disable_dp(struct intel_atomic_state *state,
 
 	drm_dp_mst_reset_vcpi_slots(&intel_dp->mst_mgr, connector->port);
 
-	ret = drm_dp_update_payload_part1(&intel_dp->mst_mgr);
+	ret = drm_dp_update_payload_part1(&intel_dp->mst_mgr, 1);
 	if (ret) {
 		drm_dbg_kms(&i915->drm, "failed to update payload %d\n", ret);
 	}
@@ -518,7 +518,7 @@ static void intel_mst_pre_enable_dp(struct intel_atomic_state *state,
 
 	intel_dp->active_mst_links++;
 
-	ret = drm_dp_update_payload_part1(&intel_dp->mst_mgr);
+	ret = drm_dp_update_payload_part1(&intel_dp->mst_mgr, 1);
 
 	/*
 	 * Before Gen 12 this is not done as part of

drivers/gpu/drm/nouveau/dispnv50/disp.c

@@ -1414,7 +1414,7 @@ nv50_mstm_prepare(struct nv50_mstm *mstm)
 	int ret;
 
 	NV_ATOMIC(drm, "%s: mstm prepare\n", mstm->outp->base.base.name);
-	ret = drm_dp_update_payload_part1(&mstm->mgr);
+	ret = drm_dp_update_payload_part1(&mstm->mgr, 1);
 
 	drm_for_each_encoder(encoder, mstm->outp->base.base.dev) {
 		if (encoder->encoder_type == DRM_MODE_ENCODER_DPMST) {

drivers/gpu/drm/radeon/radeon_dp_mst.c

@@ -423,7 +423,7 @@ radeon_mst_encoder_dpms(struct drm_encoder *encoder, int mode)
 		drm_dp_mst_allocate_vcpi(&radeon_connector->mst_port->mst_mgr,
 					 radeon_connector->port,
 					 mst_enc->pbn, slots);
-		drm_dp_update_payload_part1(&radeon_connector->mst_port->mst_mgr);
+		drm_dp_update_payload_part1(&radeon_connector->mst_port->mst_mgr, 1);
 
 		radeon_dp_mst_set_be_cntl(primary, mst_enc,
 					  radeon_connector->mst_port->hpd.hpd, true);
@@ -452,7 +452,7 @@ radeon_mst_encoder_dpms(struct drm_encoder *encoder, int mode)
 			return;
 
 		drm_dp_mst_reset_vcpi_slots(&radeon_connector->mst_port->mst_mgr, mst_enc->port);
-		drm_dp_update_payload_part1(&radeon_connector->mst_port->mst_mgr);
+		drm_dp_update_payload_part1(&radeon_connector->mst_port->mst_mgr, 1);
 
 		drm_dp_check_act_status(&radeon_connector->mst_port->mst_mgr);
 		/* and this can also fail */

include/drm/drm_dp_mst_helper.h

@@ -554,6 +554,8 @@ struct drm_dp_mst_topology_state {
 	struct drm_private_state base;
 	struct list_head vcpis;
 	struct drm_dp_mst_topology_mgr *mgr;
+	u8 total_avail_slots;
+	u8 start_slot;
 };
 
 #define to_dp_mst_topology_mgr(x) container_of(x, struct drm_dp_mst_topology_mgr, base)
@@ -806,6 +808,7 @@ int drm_dp_mst_get_vcpi_slots(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp
 
 void drm_dp_mst_reset_vcpi_slots(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port);
 
+void drm_dp_mst_update_slots(struct drm_dp_mst_topology_state *mst_state, uint8_t link_encoding_cap);
 
 void drm_dp_mst_deallocate_vcpi(struct drm_dp_mst_topology_mgr *mgr,
 				struct drm_dp_mst_port *port);
@@ -815,7 +818,7 @@ int drm_dp_find_vcpi_slots(struct drm_dp_mst_topology_mgr *mgr,
 			   int pbn);
 
 
-int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr);
+int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr, int start_slot);
 
 
 int drm_dp_update_payload_part2(struct drm_dp_mst_topology_mgr *mgr);