[PATCH v2 6/9] drm/dp: Add DP MST helpers to atomically find and release vcpi slots

[Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>]

drm_dp_atomic_find_vcpi_slots() should be called from ->atomic_check() to
check there are sufficient vcpi slots for a mode and to add that to the
state. This should be followed by a call to drm_dp_mst_allocate_vcpi()
in ->atomic_commit() to initialize a struct vcpi for the port.

drm_dp_atomic_release_vcpi_slots() should be called from
->atomic_check() to release a port's vcpi slot allocation from the
state.

Drivers that do not make use of this atomic helper are expected to call
drm_dp_find_vcpi_slots() instead before calling
drm_dp_mst_allocate_vcpi().

Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 43 +++++++++++++++++++++++++++++++++++
 include/drm/drm_dp_mst_helper.h       |  4 ++++
 2 files changed, 47 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 247286b..abebb42 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2500,6 +2500,49 @@ static int drm_dp_init_vcpi(struct drm_dp_mst_topology_mgr *mgr,
 }
 
 /**
+ * drm_dp_atomic_release_vcpi_slots() - Release allocated vcpi slots
+ * @topology_state: MST topology state
+ * @port: port to release the vcpi slots for
+ */
+int drm_dp_atomic_release_vcpi_slots(struct drm_dp_mst_topology_state *topology_state,
+				     struct drm_dp_mst_port *port)
+{
+	int alloc = drm_dp_mst_get_vcpi_slots(topology_state->mgr, port);
+
+	topology_state->avail_slots += alloc;
+	DRM_DEBUG_KMS("vcpi slots released=%d, avail=%d\n",
+			alloc, topology_state->avail_slots);
+	return alloc;
+}
+EXPORT_SYMBOL(drm_dp_atomic_release_vcpi_slots);
+
+/**
+ * drm_dp_atomic_find_vcpi_slots() - Find and add vcpi slots to the state
+ * @topology_state: MST topology state
+ * @port: port to find vcpi slots for
+ * @pbn: bandwidth required for the mode in PBN
+ */
+int drm_dp_atomic_find_vcpi_slots(struct drm_dp_mst_topology_state *topology_state,
+				  struct drm_dp_mst_port *port, int pbn)
+{
+	int num_slots, curr_alloc;
+	struct drm_dp_mst_topology_mgr *mgr = topology_state->mgr;
+
+	num_slots = DIV_ROUND_UP(pbn, mgr->pbn_div);
+	curr_alloc = drm_dp_mst_get_vcpi_slots(mgr, port);
+	DRM_DEBUG_KMS("vcpi slots req=%d, curr=%d, avail=%d\n",
+			num_slots, curr_alloc, topology_state->avail_slots);
+
+	if (num_slots - curr_alloc > topology_state->avail_slots)
+		return -ENOSPC;
+
+	topology_state->avail_slots -= (num_slots - curr_alloc);
+	DRM_DEBUG_KMS("vcpi slots avail=%d", topology_state->avail_slots);
+	return num_slots;
+}
+EXPORT_SYMBOL(drm_dp_atomic_find_vcpi_slots);
+
+/**
  * drm_dp_mst_allocate_vcpi() - Allocate a virtual channel
  * @mgr: manager for this port
  * @port: port to allocate a virtual channel for.
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 8cbdbfa..4d61269 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -615,5 +615,9 @@ void drm_dp_mst_topology_mgr_suspend(struct drm_dp_mst_topology_mgr *mgr);
 int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr);
 struct drm_dp_mst_topology_state *drm_atomic_get_mst_topology_state(struct drm_atomic_state *state,
 								    struct drm_dp_mst_topology_mgr *mgr);
+int drm_dp_atomic_find_vcpi_slots(struct drm_dp_mst_topology_state *topology_state,
+				  struct drm_dp_mst_port *port, int pbn);
+int drm_dp_atomic_release_vcpi_slots(struct drm_dp_mst_topology_state *topology_state,
+				     struct drm_dp_mst_port *port);
 
 #endif
-- 
2.7.4

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