iwlwifi: don't count the tfds in HW queue any more

Since packets sent to an RA / TID in AGG are sent from a
separate HW Tx queue, we may get into a race:
the regular queue isn't empty while we already begin to
send packets from the AGG queue. This would result in sending
packets out of order.

In order to cope with this, mac80211 waits until the driver
reports that the legacy queue is drained before it can send
packets to the AGG queue. During that time, mac80211 buffers
packets for the driver. These packets will be sent in order
after the driver reports it is ready.

The way this was implemented in the driver is as follows:
We held a counter that monitors the number of packets for
an RA / TID in the HW queues. When this counter reached 0,
we knew that the HW queues were drained and we reported to
mac80211 that were ready to proceed.

This patch changes the implementation described above. We
now remember what is the wifi sequence number of the first
packet that will be sent in the AGG queue (lets' call it
ssn). When we reclaim the packet before ssn, we know that
the queue is drained, and we are ready to proceed.

This will allow us to move this logic in the upper layer and
eventually remove the tid_data from the shared area.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl-shared.h b/drivers/net/wireless/iwlwifi/iwl-shared.h
index df6d2123fe4f..8a9690714c13 100644
--- a/drivers/net/wireless/iwlwifi/iwl-shared.h
+++ b/drivers/net/wireless/iwlwifi/iwl-shared.h
@@ -231,12 +231,17 @@ enum iwl_agg_state {
  * @state: state of the BA agreement establishment / tear down.
  * @txq_id: Tx queue used by the BA session - used by the transport layer.
  *      Needed by the upper layer for debugfs only.
+ * @ssn: the first packet to be sent in AGG HW queue in Tx AGG start flow, or
+ *      the first packet to be sent in legacy HW queue in Tx AGG stop flow.
+ *      Basically when next_reclaimed reaches ssn, we can tell mac80211 that
+ *      we are ready to finish the Tx AGG stop / start flow.
  * @wait_for_ba: Expect block-ack before next Tx reply
  */
 struct iwl_ht_agg {
         u32 rate_n_flags;
         enum iwl_agg_state state;
         u16 txq_id;
+        u16 ssn;
         bool wait_for_ba;
 };
 
@@ -246,13 +251,13 @@ struct iwl_ht_agg {
  * This structs holds the states for each RA / TID.
 
  * @seq_number: the next WiFi sequence number to use
- * @tfds_in_queue: number of packets sent to the HW queues.
- *      Exported for debugfs only
+ * @next_reclaimed: the WiFi sequence number of the next packet to be acked.
+ *      This is basically (last acked packet++).
  * @agg: aggregation state machine
  */
 struct iwl_tid_data {
         u16 seq_number;
-        u16 tfds_in_queue;
+        u16 next_reclaimed;
         struct iwl_ht_agg agg;
 };