mac80211: Add airtime account and scheduling to TXQs

This adds airtime accounting and scheduling to the mac80211 TXQ
scheduler. A new hardware flag, AIRTIME_ACCOUNTING, is added that
drivers can set if they support reporting airtime usage of
transmissions. When this flag is set, mac80211 will expect the actual
airtime usage to be reported in the tx_time and rx_time fields of the
respective status structs.

When airtime information is present, mac80211 will schedule TXQs
(through ieee80211_next_txq()) in a way that enforces airtime fairness
between active stations. This scheduling works the same way as the ath9k
in-driver airtime fairness scheduling.

Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 45155803c875..531b526a10db 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -1188,6 +1188,8 @@ enum mac80211_rx_encoding {
  *	HT or VHT is used (%RX_FLAG_HT/%RX_FLAG_VHT)
  * @nss: number of streams (VHT and HE only)
  * @flag: %RX_FLAG_\*
+ * @airtime: Duration of frame in usec. See @IEEE80211_HW_AIRTIME_ACCOUNTING for
+ *       how to use this.
  * @encoding: &enum mac80211_rx_encoding
  * @bw: &enum rate_info_bw
  * @enc_flags: uses bits from &enum mac80211_rx_encoding_flags
@@ -1202,6 +1204,7 @@ struct ieee80211_rx_status {
 	u32 device_timestamp;
 	u32 ampdu_reference;
 	u32 flag;
+	u16 airtime;
 	u16 freq;
 	u8 enc_flags;
 	u8 encoding:2, bw:3;
@@ -2066,6 +2069,26 @@ struct ieee80211_txq {
  * @IEEE80211_HW_SUPPORTS_TDLS_BUFFER_STA: Hardware supports buffer STA on
  *	TDLS links.
  *
+ * @IEEE80211_HW_AIRTIME_ACCOUNTING: Hardware supports accounting the airtime
+ *      usage of other stations and reports it in the @tx_time and/or @airtime
+ *      fields of the TX/RX status structs.
+ *      When setting this flag, the driver should ensure that the respective
+ *      fields in the TX and RX status structs are always either zero or
+ *      contains a valid duration for the frame in usec. The driver can choose
+ *      to report either or both of TX and RX airtime, but it is recommended to
+ *      report both.
+ *      The reported airtime should as a minimum include all time that is spent
+ *      transmitting to the remote station, including overhead and padding, but
+ *      not including time spent waiting for a TXOP. If the time is not reported
+ *      by the hardware it can in some cases be calculated from the rate and
+ *      known frame composition. When possible, the time should include any
+ *      failed transmission attempts.
+ *      For aggregated frames, there are two possible strategies to report the
+ *      airtime: Either include the airtime of the entire aggregate in the first
+ *      (or last) frame and leave the others at zero. Alternatively, include the
+ *      overhead of the full aggregate in the first or last frame and report the
+ *      time of each frame + padding not including the full aggregate overhead.
+ *
  * @NUM_IEEE80211_HW_FLAGS: number of hardware flags, used for sizing arrays
  */
 enum ieee80211_hw_flags {
@@ -2109,6 +2132,7 @@ enum ieee80211_hw_flags {
 	IEEE80211_HW_REPORTS_LOW_ACK,
 	IEEE80211_HW_SUPPORTS_TX_FRAG,
 	IEEE80211_HW_SUPPORTS_TDLS_BUFFER_STA,
+	IEEE80211_HW_AIRTIME_ACCOUNTING,
 
 	/* keep last, obviously */
 	NUM_IEEE80211_HW_FLAGS