Merge tag 'topic/mst-bw-check-fixes-for-airlied-2020-03-12-2' of git://anongit.freedesktop.org/drm/drm-misc into drm-fixes

UAPI Changes: None

Cross-subsystem Changes: None

Core Changes: Fixed regressions introduced by commit cd82d82cbc04
("drm/dp_mst: Add branch bandwidth validation to MST atomic check"),
which would cause us to:

* Calculate the available bandwidth on an MST topology incorrectly, and
  as a result reject most display configurations that would try to enable
  more then one sink on a topology
* Occasionally expose MST connectors to userspace before finishing
  probing their PBN capabilities, resulting in us rejecting display
  configurations because we assumed briefly that no bandwidth was
  available

Driver Changes: None

Signed-off-by: Dave Airlie <airlied@redhat.com>
From: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/bf16ee577567beed91c86b7d9cda3ec2e8c50a71.camel@redhat.com
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index cce0b1b..ed0fea2 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -1935,7 +1935,7 @@
 	return parent_lct + 1;
 }
 
-static bool drm_dp_mst_is_dp_mst_end_device(u8 pdt, bool mcs)
+static bool drm_dp_mst_is_end_device(u8 pdt, bool mcs)
 {
 	switch (pdt) {
 	case DP_PEER_DEVICE_DP_LEGACY_CONV:
@@ -1965,13 +1965,13 @@
 
 	/* Teardown the old pdt, if there is one */
 	if (port->pdt != DP_PEER_DEVICE_NONE) {
-		if (drm_dp_mst_is_dp_mst_end_device(port->pdt, port->mcs)) {
+		if (drm_dp_mst_is_end_device(port->pdt, port->mcs)) {
 			/*
 			 * If the new PDT would also have an i2c bus,
 			 * don't bother with reregistering it
 			 */
 			if (new_pdt != DP_PEER_DEVICE_NONE &&
-			    drm_dp_mst_is_dp_mst_end_device(new_pdt, new_mcs)) {
+			    drm_dp_mst_is_end_device(new_pdt, new_mcs)) {
 				port->pdt = new_pdt;
 				port->mcs = new_mcs;
 				return 0;
@@ -1991,7 +1991,7 @@
 	port->mcs = new_mcs;
 
 	if (port->pdt != DP_PEER_DEVICE_NONE) {
-		if (drm_dp_mst_is_dp_mst_end_device(port->pdt, port->mcs)) {
+		if (drm_dp_mst_is_end_device(port->pdt, port->mcs)) {
 			/* add i2c over sideband */
 			ret = drm_dp_mst_register_i2c_bus(&port->aux);
 		} else {
@@ -2172,7 +2172,7 @@
 	}
 
 	if (port->pdt != DP_PEER_DEVICE_NONE &&
-	    drm_dp_mst_is_dp_mst_end_device(port->pdt, port->mcs)) {
+	    drm_dp_mst_is_end_device(port->pdt, port->mcs)) {
 		port->cached_edid = drm_get_edid(port->connector,
 						 &port->aux.ddc);
 		drm_connector_set_tile_property(port->connector);
@@ -2302,14 +2302,18 @@
 		mutex_unlock(&mgr->lock);
 	}
 
-	if (old_ddps != port->ddps) {
-		if (port->ddps) {
-			if (!port->input) {
-				drm_dp_send_enum_path_resources(mgr, mstb,
-								port);
-			}
+	/*
+	 * Reprobe PBN caps on both hotplug, and when re-probing the link
+	 * for our parent mstb
+	 */
+	if (old_ddps != port->ddps || !created) {
+		if (port->ddps && !port->input) {
+			ret = drm_dp_send_enum_path_resources(mgr, mstb,
+							      port);
+			if (ret == 1)
+				changed = true;
 		} else {
-			port->available_pbn = 0;
+			port->full_pbn = 0;
 		}
 	}
 
@@ -2401,11 +2405,10 @@
 	port->ddps = conn_stat->displayport_device_plug_status;
 
 	if (old_ddps != port->ddps) {
-		if (port->ddps) {
-			dowork = true;
-		} else {
-			port->available_pbn = 0;
-		}
+		if (port->ddps && !port->input)
+			drm_dp_send_enum_path_resources(mgr, mstb, port);
+		else
+			port->full_pbn = 0;
 	}
 
 	new_pdt = port->input ? DP_PEER_DEVICE_NONE : conn_stat->peer_device_type;
@@ -2556,13 +2559,6 @@
 		if (port->input || !port->ddps)
 			continue;
 
-		if (!port->available_pbn) {
-			drm_modeset_lock(&mgr->base.lock, NULL);
-			drm_dp_send_enum_path_resources(mgr, mstb, port);
-			drm_modeset_unlock(&mgr->base.lock);
-			changed = true;
-		}
-
 		if (port->mstb)
 			mstb_child = drm_dp_mst_topology_get_mstb_validated(
 			    mgr, port->mstb);
@@ -2990,6 +2986,7 @@
 
 	ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
 	if (ret > 0) {
+		ret = 0;
 		path_res = &txmsg->reply.u.path_resources;
 
 		if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK) {
@@ -3002,14 +2999,22 @@
 				      path_res->port_number,
 				      path_res->full_payload_bw_number,
 				      path_res->avail_payload_bw_number);
-			port->available_pbn =
-				path_res->avail_payload_bw_number;
+
+			/*
+			 * If something changed, make sure we send a
+			 * hotplug
+			 */
+			if (port->full_pbn != path_res->full_payload_bw_number ||
+			    port->fec_capable != path_res->fec_capable)
+				ret = 1;
+
+			port->full_pbn = path_res->full_payload_bw_number;
 			port->fec_capable = path_res->fec_capable;
 		}
 	}
 
 	kfree(txmsg);
-	return 0;
+	return ret;
 }
 
 static struct drm_dp_mst_port *drm_dp_get_last_connected_port_to_mstb(struct drm_dp_mst_branch *mstb)
@@ -3596,13 +3601,9 @@
 	/* The link address will need to be re-sent on resume */
 	mstb->link_address_sent = false;
 
-	list_for_each_entry(port, &mstb->ports, next) {
-		/* The PBN for each port will also need to be re-probed */
-		port->available_pbn = 0;
-
+	list_for_each_entry(port, &mstb->ports, next)
 		if (port->mstb)
 			drm_dp_mst_topology_mgr_invalidate_mstb(port->mstb);
-	}
 }
 
 /**
@@ -4829,41 +4830,102 @@
 	return false;
 }
 
-static inline
-int drm_dp_mst_atomic_check_bw_limit(struct drm_dp_mst_branch *branch,
-				     struct drm_dp_mst_topology_state *mst_state)
+static int
+drm_dp_mst_atomic_check_port_bw_limit(struct drm_dp_mst_port *port,
+				      struct drm_dp_mst_topology_state *state);
+
+static int
+drm_dp_mst_atomic_check_mstb_bw_limit(struct drm_dp_mst_branch *mstb,
+				      struct drm_dp_mst_topology_state *state)
 {
-	struct drm_dp_mst_port *port;
 	struct drm_dp_vcpi_allocation *vcpi;
-	int pbn_limit = 0, pbn_used = 0;
+	struct drm_dp_mst_port *port;
+	int pbn_used = 0, ret;
+	bool found = false;
 
-	list_for_each_entry(port, &branch->ports, next) {
-		if (port->mstb)
-			if (drm_dp_mst_atomic_check_bw_limit(port->mstb, mst_state))
-				return -ENOSPC;
-
-		if (port->available_pbn > 0)
-			pbn_limit = port->available_pbn;
-	}
-	DRM_DEBUG_ATOMIC("[MST BRANCH:%p] branch has %d PBN available\n",
-			 branch, pbn_limit);
-
-	list_for_each_entry(vcpi, &mst_state->vcpis, next) {
-		if (!vcpi->pbn)
+	/* Check that we have at least one port in our state that's downstream
+	 * of this branch, otherwise we can skip this branch
+	 */
+	list_for_each_entry(vcpi, &state->vcpis, next) {
+		if (!vcpi->pbn ||
+		    !drm_dp_mst_port_downstream_of_branch(vcpi->port, mstb))
 			continue;
 
-		if (drm_dp_mst_port_downstream_of_branch(vcpi->port, branch))
-			pbn_used += vcpi->pbn;
+		found = true;
+		break;
 	}
-	DRM_DEBUG_ATOMIC("[MST BRANCH:%p] branch used %d PBN\n",
-			 branch, pbn_used);
+	if (!found)
+		return 0;
 
-	if (pbn_used > pbn_limit) {
-		DRM_DEBUG_ATOMIC("[MST BRANCH:%p] No available bandwidth\n",
-				 branch);
+	if (mstb->port_parent)
+		DRM_DEBUG_ATOMIC("[MSTB:%p] [MST PORT:%p] Checking bandwidth limits on [MSTB:%p]\n",
+				 mstb->port_parent->parent, mstb->port_parent,
+				 mstb);
+	else
+		DRM_DEBUG_ATOMIC("[MSTB:%p] Checking bandwidth limits\n",
+				 mstb);
+
+	list_for_each_entry(port, &mstb->ports, next) {
+		ret = drm_dp_mst_atomic_check_port_bw_limit(port, state);
+		if (ret < 0)
+			return ret;
+
+		pbn_used += ret;
+	}
+
+	return pbn_used;
+}
+
+static int
+drm_dp_mst_atomic_check_port_bw_limit(struct drm_dp_mst_port *port,
+				      struct drm_dp_mst_topology_state *state)
+{
+	struct drm_dp_vcpi_allocation *vcpi;
+	int pbn_used = 0;
+
+	if (port->pdt == DP_PEER_DEVICE_NONE)
+		return 0;
+
+	if (drm_dp_mst_is_end_device(port->pdt, port->mcs)) {
+		bool found = false;
+
+		list_for_each_entry(vcpi, &state->vcpis, next) {
+			if (vcpi->port != port)
+				continue;
+			if (!vcpi->pbn)
+				return 0;
+
+			found = true;
+			break;
+		}
+		if (!found)
+			return 0;
+
+		/* This should never happen, as it means we tried to
+		 * set a mode before querying the full_pbn
+		 */
+		if (WARN_ON(!port->full_pbn))
+			return -EINVAL;
+
+		pbn_used = vcpi->pbn;
+	} else {
+		pbn_used = drm_dp_mst_atomic_check_mstb_bw_limit(port->mstb,
+								 state);
+		if (pbn_used <= 0)
+			return pbn_used;
+	}
+
+	if (pbn_used > port->full_pbn) {
+		DRM_DEBUG_ATOMIC("[MSTB:%p] [MST PORT:%p] required PBN of %d exceeds port limit of %d\n",
+				 port->parent, port, pbn_used,
+				 port->full_pbn);
 		return -ENOSPC;
 	}
-	return 0;
+
+	DRM_DEBUG_ATOMIC("[MSTB:%p] [MST PORT:%p] uses %d out of %d PBN\n",
+			 port->parent, port, pbn_used, port->full_pbn);
+
+	return pbn_used;
 }
 
 static inline int
@@ -5061,9 +5123,15 @@
 		ret = drm_dp_mst_atomic_check_vcpi_alloc_limit(mgr, mst_state);
 		if (ret)
 			break;
-		ret = drm_dp_mst_atomic_check_bw_limit(mgr->mst_primary, mst_state);
-		if (ret)
+
+		mutex_lock(&mgr->lock);
+		ret = drm_dp_mst_atomic_check_mstb_bw_limit(mgr->mst_primary,
+							    mst_state);
+		mutex_unlock(&mgr->lock);
+		if (ret < 0)
 			break;
+		else
+			ret = 0;
 	}
 
 	return ret;
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index bcb39da..41725d8 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -81,7 +81,7 @@
  * &drm_dp_mst_topology_mgr.base.lock.
  * @num_sdp_stream_sinks: Number of stream sinks. Protected by
  * &drm_dp_mst_topology_mgr.base.lock.
- * @available_pbn: Available bandwidth for this port. Protected by
+ * @full_pbn: Max possible bandwidth for this port. Protected by
  * &drm_dp_mst_topology_mgr.base.lock.
  * @next: link to next port on this branch device
  * @aux: i2c aux transport to talk to device connected to this port, protected
@@ -126,7 +126,7 @@
 	u8 dpcd_rev;
 	u8 num_sdp_streams;
 	u8 num_sdp_stream_sinks;
-	uint16_t available_pbn;
+	uint16_t full_pbn;
 	struct list_head next;
 	/**
 	 * @mstb: the branch device connected to this port, if there is one.