From: Mikita Lipski <mikita.lip...@amd.com>

Adding a helper function to be called by
drivers outside of DRM to enable DSC on
the MST ports.

Function is called to recalculate VCPI allocation
if DSC is enabled and raise the DSC flag to enable.
In case of disabling DSC the flag is set to false
and recalculation of VCPI slots is expected to be done
in encoder's atomic_check.

v2: squash separate functions into one and call it per
port

Cc: Harry Wentland <harry.wentl...@amd.com>
Cc: Lyude Paul <ly...@redhat.com>
Signed-off-by: Mikita Lipski <mikita.lip...@amd.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 61 +++++++++++++++++++++++++++
 include/drm/drm_dp_mst_helper.h       |  5 +++
 2 files changed, 66 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c 
b/drivers/gpu/drm/drm_dp_mst_topology.c
index f1d883960831..5e549f48ffb8 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -4742,6 +4742,67 @@ drm_dp_mst_atomic_check_topology_state(struct 
drm_dp_mst_topology_mgr *mgr,
        return 0;
 }
 
+/**
+ * drm_dp_mst_atomic_enable_dsc - Set DSC Enable Flag to On/Off
+ * @state: Pointer to the new drm_atomic_state
+ * @pointer: Pointer to the affected MST Port
+ * @pbn: Newly recalculated bw required for link with DSC enabled
+ * @pbn_div: Divider to calculate correct number of pbn per slot
+ * @enable: Boolean flag enabling or disabling DSC on the port
+ *
+ * This function enables DSC on the given Port
+ * by recalculating its vcpi from pbn provided
+ * and sets dsc_enable flag to keep track of which
+ * ports have DSC enabled
+ *
+ */
+int drm_dp_mst_atomic_enable_dsc(struct drm_atomic_state *state,
+                                struct drm_dp_mst_port *port,
+                                int pbn, int pbn_div,
+                                bool enable)
+{
+       struct drm_dp_mst_topology_state *mst_state;
+       struct drm_dp_vcpi_allocation *pos;
+       bool found = false;
+       int vcpi = 0;
+
+       mst_state = drm_atomic_get_mst_topology_state(state, port->mgr);
+
+       if (IS_ERR(mst_state))
+               return PTR_ERR(mst_state);
+
+       list_for_each_entry(pos, &mst_state->vcpis, next) {
+               if (pos->port == port) {
+                       found = true;
+                       break;
+               }
+       }
+
+       if (!found) {
+               DRM_DEBUG_ATOMIC("[MST PORT:%p] Couldn't find VCPI allocation 
in mst state %p\n",
+                                port, mst_state);
+               return -EINVAL;
+       }
+
+       if (pos->dsc_enabled == enable) {
+               DRM_DEBUG_ATOMIC("[MST PORT:%p] DSC flag is already set to %d, 
returning %d VCPI slots\n",
+                                port, enable, pos->vcpi);
+               vcpi = pos->vcpi;
+       }
+
+       if (enable) {
+               vcpi = drm_dp_atomic_find_vcpi_slots(state, port->mgr, port, 
pbn, pbn_div);
+               DRM_DEBUG_ATOMIC("[MST PORT:%p] Enabling DSC flag, reallocating 
%d VCPI slots on the port\n",
+                                port, vcpi);
+               if (vcpi < 0)
+                       return -EINVAL;
+       }
+
+       pos->dsc_enabled = enable;
+
+       return vcpi;
+}
+EXPORT_SYMBOL(drm_dp_mst_atomic_enable_dsc);
 /**
  * drm_dp_mst_atomic_check - Check that the new state of an MST topology in an
  * atomic update is valid
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 0f813d6346aa..830c94b7f45d 100644
--- 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;
+       bool dsc_enabled;
        struct list_head next;
 };
 
@@ -773,6 +774,10 @@ drm_dp_atomic_find_vcpi_slots(struct drm_atomic_state 
*state,
                              struct drm_dp_mst_topology_mgr *mgr,
                              struct drm_dp_mst_port *port, int pbn,
                              int pbn_div);
+int drm_dp_mst_atomic_enable_dsc(struct drm_atomic_state *state,
+                                struct drm_dp_mst_port *port,
+                                int pbn, int pbn_div,
+                                bool enable);
 int __must_check
 drm_dp_atomic_release_vcpi_slots(struct drm_atomic_state *state,
                                 struct drm_dp_mst_topology_mgr *mgr,
-- 
2.17.1

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