[PATCH v3 5/8] drm/dp: Introduce MST topology state to track available link bandwidth

[Dhinakaran Pandiyan]

Link bandwidth is shared between multiple display streams in DP MST
configurations. The DP MST topology manager structure maintains the
shared link bandwidth for a primary link directly connected to the GPU. For
atomic modesetting drivers, checking if there is sufficient link bandwidth
for a mode needs to be done during the atomic_check phase to avoid failed
modesets. Let's encapsulate the available link bw information in a
private state structure so that bw can be allocated and released atomically
for each of the ports sharing the primary link.

v2: Included kernel doc, moved state initialization and switched to
kmemdup() for allocation (Daniel)

Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 71 +++++++++++++++++++++++++++++++++++
 include/drm/drm_dp_mst_helper.h       | 20 ++++++++++
 2 files changed, 91 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 37482b7..a891c36 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2936,6 +2936,65 @@ static void drm_dp_destroy_connector_work(struct work_struct *work)
 		(*mgr->cbs->hotplug)(mgr);
 }
 
+void *drm_dp_mst_duplicate_state(struct drm_atomic_state *state, void *obj)
+{
+	struct drm_dp_mst_topology_mgr *mgr = obj;
+	struct drm_dp_mst_topology_state *new_mst_state;
+
+	if (WARN_ON(!mgr->state))
+		return NULL;
+
+	new_mst_state = kmemdup(mgr->state, sizeof(*new_mst_state), GFP_KERNEL);
+	if (new_mst_state)
+		new_mst_state->state = state;
+	return new_mst_state;
+}
+
+void drm_dp_mst_swap_state(void *obj, void **obj_state_ptr)
+{
+	struct drm_dp_mst_topology_mgr *mgr = obj;
+	struct drm_dp_mst_topology_state **topology_state_ptr;
+
+	topology_state_ptr = (struct drm_dp_mst_topology_state **)obj_state_ptr;
+
+	mgr->state->state = (*topology_state_ptr)->state;
+	swap(*topology_state_ptr, mgr->state);
+	mgr->state->state = NULL;
+}
+
+void drm_dp_mst_destroy_state(void *obj_state)
+{
+	kfree(obj_state);
+}
+
+static const struct drm_private_state_funcs mst_state_funcs = {
+	.duplicate_state = drm_dp_mst_duplicate_state,
+	.swap_state = drm_dp_mst_swap_state,
+	.destroy_state = drm_dp_mst_destroy_state,
+};
+
+/**
+ * drm_atomic_get_mst_topology_state: get MST topology state
+ *
+ * @state: global atomic state
+ * @mgr: MST topology manager, also the private object in this case
+ *
+ * This function wraps drm_atomic_get_priv_obj_state() passing in the MST atomic
+ * state vtable so that the private object state returned is that of a MST
+ * topology object.
+ *
+ * RETURNS:
+ *
+ * The MST topology state or error pointer.
+ */
+struct drm_dp_mst_topology_state *drm_atomic_get_mst_topology_state(struct drm_atomic_state *state,
+								    struct drm_dp_mst_topology_mgr *mgr)
+{
+		return drm_atomic_get_private_obj_state(state, mgr,
+							&mst_state_funcs);
+}
+EXPORT_SYMBOL(drm_atomic_get_mst_topology_state);
+
 /**
  * drm_dp_mst_topology_mgr_init - initialise a topology manager
  * @mgr: manager struct to initialise
@@ -2980,6 +3039,15 @@ int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr,
 	if (test_calc_pbn_mode() < 0)
 		DRM_ERROR("MST PBN self-test failed\n");
 
+	mgr->state = kzalloc(sizeof(*mgr->state), GFP_KERNEL);
+	if (mgr->state == NULL)
+		return -ENOMEM;
+	mgr->state->mgr = mgr;
+
+	/* max. time slots - one slot for MTP header */
+	mgr->state->avail_slots = 63;
+	mgr->funcs = &mst_state_funcs;
+
 	return 0;
 }
 EXPORT_SYMBOL(drm_dp_mst_topology_mgr_init);
@@ -3000,6 +3068,9 @@ void drm_dp_mst_topology_mgr_destroy(struct drm_dp_mst_topology_mgr *mgr)
 	mutex_unlock(&mgr->payload_lock);
 	mgr->dev = NULL;
 	mgr->aux = NULL;
+	kfree(mgr->state);
+	mgr->state = NULL;
+	mgr->funcs = NULL;
 }
 EXPORT_SYMBOL(drm_dp_mst_topology_mgr_destroy);
 
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 5b02476..0b371df 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -24,6 +24,7 @@
 
 #include <linux/types.h>
 #include <drm/drm_dp_helper.h>
+#include <drm/drm_atomic.h>
 
 struct drm_dp_mst_branch;
 
@@ -403,6 +404,12 @@ struct drm_dp_payload {
 	int vcpi;
 };
 
+struct drm_dp_mst_topology_state {
+	int avail_slots;
+	struct drm_atomic_state *state;
+	struct drm_dp_mst_topology_mgr *mgr;
+};
+
 /**
  * struct drm_dp_mst_topology_mgr - DisplayPort MST manager
  *
@@ -481,6 +488,16 @@ struct drm_dp_mst_topology_mgr {
 	int pbn_div;
 
 	/**
+	 * @state: State information for topology manager
+	 */
+	struct drm_dp_mst_topology_state *state;
+
+	/**
+	 * @funcs: Atomic helper callbacks
+	 */
+	const struct drm_private_state_funcs *funcs;
+
+	/**
 	 * @qlock: protects @tx_msg_downq, the &drm_dp_mst_branch.txslost and
 	 * &drm_dp_sideband_msg_tx.state once they are queued
 	 */
@@ -596,4 +613,7 @@ void drm_dp_mst_dump_topology(struct seq_file *m,
 
 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);
+
 #endif
-- 
2.7.4