iwlwifi: mvm: cleanup references to aggregation count limit

Currently the code is mixing defines and is inconsistent.
When enabling a queue, we usually configure the scheduler
with IWL_FRAME_LIMIT - 64.
When sending to firmware the rate scaling, we limit aggregation
to LINK_QUAL_AGG_FRAME_LIMIT_DEF - 63, due to a scheduler bug.
Given that, clean up the following:
- Fix a stray queue enablement with LINK_QUAL_AGG_FRAME_LIMIT_DEF.
- Change the comparison that tests if queue needs to be reconfigured
  to be compared directly to how it was configured.
  This also saves the redundant round down of the buffer size just
  for the sake of comparing it, making the code more readable.
- Better document gen2 logic
Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

drivers/net/wireless/intel/iwlwifi/mvm/sta.c

@@ -644,8 +644,7 @@ int iwl_mvm_scd_queue_redirect(struct iwl_mvm *mvm, int queue, int tid,
 
 	/* Redirect to lower AC */
 	iwl_mvm_reconfig_scd(mvm, queue, iwl_mvm_ac_to_tx_fifo[ac],
-			     cmd.sta_id, tid, LINK_QUAL_AGG_FRAME_LIMIT_DEF,
-			     ssn);
+			     cmd.sta_id, tid, IWL_FRAME_LIMIT, ssn);
 
 	/* Update AC marking of the queue */
 	spin_lock_bh(&mvm->queue_info_lock);
@@ -2544,12 +2543,6 @@ int iwl_mvm_sta_tx_agg_oper(struct iwl_mvm *mvm, struct ieee80211_vif *vif,
 	BUILD_BUG_ON((sizeof(mvmsta->agg_tids) * BITS_PER_BYTE)
 		     != IWL_MAX_TID_COUNT);
 
-	if (!mvm->trans->cfg->gen2)
-		buf_size = min_t(int, buf_size, LINK_QUAL_AGG_FRAME_LIMIT_DEF);
-	else
-		buf_size = min_t(int, buf_size,
-				 LINK_QUAL_AGG_FRAME_LIMIT_GEN2_DEF);
-
 	spin_lock_bh(&mvmsta->lock);
 	ssn = tid_data->ssn;
 	queue = tid_data->txq_id;
@@ -2561,10 +2554,17 @@ int iwl_mvm_sta_tx_agg_oper(struct iwl_mvm *mvm, struct ieee80211_vif *vif,
 
 	if (iwl_mvm_has_new_tx_api(mvm)) {
 		/*
-		 * If no queue iwl_mvm_sta_tx_agg_start() would have failed so
-		 * no need to check queue's status
-		 */
-		if (buf_size < mvmsta->max_agg_bufsize)
+		 * If there is no queue for this tid, iwl_mvm_sta_tx_agg_start()
+		 * would have failed, so if we are here there is no need to
+		 * allocate a queue.
+		 * However, if aggregation size is different than the default
+		 * size, the scheduler should be reconfigured.
+		 * We cannot do this with the new TX API, so return unsupported
+		 * for now, until it will be offloaded to firmware..
+		 * Note that if SCD default value changes - this condition
+		 * should be updated as well.
+		 */
+		if (buf_size < IWL_FRAME_LIMIT)
 			return -ENOTSUPP;
 
 		ret = iwl_mvm_sta_tx_agg(mvm, sta, tid, queue, true);
@@ -2587,7 +2587,7 @@ int iwl_mvm_sta_tx_agg_oper(struct iwl_mvm *mvm, struct ieee80211_vif *vif,
 	 * Only reconfig the SCD for the queue if the window size has
 	 * changed from current (become smaller)
 	 */
-	if (!alloc_queue && buf_size < mvmsta->max_agg_bufsize) {
+	if (!alloc_queue && buf_size < IWL_FRAME_LIMIT) {
 		/*
 		 * If reconfiguring an existing queue, it first must be
 		 * drained