This switches ath9k over to using the mac80211 intermediate software queueing mechanism for data packets. It removes the queueing inside the driver, except for the retry queue, and instead pulls from mac80211 when a packet is needed. The retry queue is used to store a packet that was pulled but can't be sent immediately. The old code path in ath_tx_start that would queue packets has been removed completely, as has the qlen limit tunables (since there's no longer a queue in the driver to limit). The mac80211 intermediate software queues offer significant latency reductions, and this patch allows ath9k to realise them. The exact gains from this varies with the test scenario, but in an access point scenario we have seen latency reductions ranging from 1/3 to as much as an order of magnitude. We also achieve slightly better aggregation. Median latency (ping) figures with this patch applied at the access point, with two high-rate stations and one low-rate station (HT20 5Ghz), running a Flent rtt_fair_var_up test with one TCP flow and one ping flow going to each station: Fast station Slow station Default pfifo_fast qdisc: 430.4 ms 638.7 ms fq_codel qdisc on iface: 35.5 ms 211.8 ms This patch set: 22.4 ms 38.2 ms Median aggregation sizes over the same test: Default pfifo_fast qdisc: 9.5 pkts 1.9 pkts fq_codel qdisc on iface: 11.2 pkts 1.9 pkts This patch set: 13.9 pkts 1.9 pkts This patch is based on Tim's original patch set, but reworked quite thoroughly. Cc: Tim Shepard <shep@alum.mit.edu> Cc: Felix Fietkau <nbd@nbd.name> Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk> Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>