drm/dp_mst: Add branch bandwidth validation to MST atomic check

[why]
Adding PBN attribute to drm_dp_vcpi_allocation structure to
keep track of how much bandwidth each Port requires.
Adding drm_dp_mst_atomic_check_bw_limit to verify that
state's bandwidth needs doesn't exceed available bandwidth.
The funtion is called in drm_dp_mst_atomic_check after
drm_dp_mst_atomic_check_topology_state to fully verify that
the proposed topology is supported.

v2: Fixing some typos and indenting
v3: Return correct error enums if no bw space available

Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 9f7e714c518256ce6cd16a1429af7017b1f6e427..c7bea8a957975a24970057904da987652cc18eb8 100644 (file)
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -4125,7 +4125,7 @@ int drm_dp_atomic_find_vcpi_slots(struct drm_atomic_state *state,
 {
        struct drm_dp_mst_topology_state *topology_state;
        struct drm_dp_vcpi_allocation *pos, *vcpi = NULL;
-       int prev_slots, req_slots;
+       int prev_slots, prev_bw, req_slots;
 
        topology_state = drm_atomic_get_mst_topology_state(state, mgr);
        if (IS_ERR(topology_state))
@@ -4136,6 +4136,7 @@ int drm_dp_atomic_find_vcpi_slots(struct drm_atomic_state *state,
                if (pos->port == port) {
                        vcpi = pos;
                        prev_slots = vcpi->vcpi;
+                       prev_bw = vcpi->pbn;
 
                        /*
                         * This should never happen, unless the driver tries
@@ -4151,8 +4152,10 @@ int drm_dp_atomic_find_vcpi_slots(struct drm_atomic_state *state,
                        break;
                }
        }
-       if (!vcpi)
+       if (!vcpi) {
                prev_slots = 0;
+               prev_bw = 0;
+       }
 
        if (pbn_div <= 0)
                pbn_div = mgr->pbn_div;
@@ -4162,6 +4165,9 @@ int drm_dp_atomic_find_vcpi_slots(struct drm_atomic_state *state,
        DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] [MST PORT:%p] VCPI %d -> %d\n",
                         port->connector->base.id, port->connector->name,
                         port, prev_slots, req_slots);
+       DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] [MST PORT:%p] PBN %d -> %d\n",
+                        port->connector->base.id, port->connector->name,
+                        port, prev_bw, pbn);
 
        /* Add the new allocation to the state */
        if (!vcpi) {
@@ -4174,6 +4180,7 @@ int drm_dp_atomic_find_vcpi_slots(struct drm_atomic_state *state,
                list_add(&vcpi->next, &topology_state->vcpis);
        }
        vcpi->vcpi = req_slots;
+       vcpi->pbn = pbn;
 
        return req_slots;
 }
@@ -4750,6 +4757,58 @@ static void drm_dp_mst_destroy_state(struct drm_private_obj *obj,
        kfree(mst_state);
 }
 
+static bool drm_dp_mst_port_downstream_of_branch(struct drm_dp_mst_port *port,
+                                                struct drm_dp_mst_branch *branch)
+{
+       while (port->parent) {
+               if (port->parent == branch)
+                       return true;
+
+               if (port->parent->port_parent)
+                       port = port->parent->port_parent;
+               else
+                       break;
+       }
+       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)
+{
+       struct drm_dp_mst_port *port;
+       struct drm_dp_vcpi_allocation *vcpi;
+       int pbn_limit = 0, pbn_used = 0;
+
+       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)
+                       continue;
+
+               if (drm_dp_mst_port_downstream_of_branch(vcpi->port, branch))
+                       pbn_used += vcpi->pbn;
+       }
+       DRM_DEBUG_ATOMIC("[MST BRANCH:%p] branch used %d PBN\n",
+                        branch, pbn_used);
+
+       if (pbn_used > pbn_limit) {
+               DRM_DEBUG_ATOMIC("[MST BRANCH:%p] No available bandwidth\n",
+                                branch);
+               return -ENOSPC;
+       }
+       return 0;
+}
+
 static inline int
 drm_dp_mst_atomic_check_topology_state(struct drm_dp_mst_topology_mgr *mgr,
                                       struct drm_dp_mst_topology_state *mst_state)
@@ -4881,6 +4940,9 @@ int drm_dp_mst_atomic_check(struct drm_atomic_state *state)
                ret = drm_dp_mst_atomic_check_topology_state(mgr, mst_state);
                if (ret)
                        break;
+               ret = drm_dp_mst_atomic_check_bw_limit(mgr->mst_primary, mst_state);
+               if (ret)
+                       break;
        }
 
        return ret;

diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 14ccda19d9cc06380a64d04539f047f54097539c..d940f45c76373e3871e63b47362cece9907d879e 100644 (file)
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -502,6 +502,7 @@ struct drm_dp_payload {
 struct drm_dp_vcpi_allocation {
        struct drm_dp_mst_port *port;
        int vcpi;
+       int pbn;
        bool dsc_enabled;
        struct list_head next;
 };