for Atheros AR5416 and later wireless devices.
This is a very large commit - the complete history can be
found in the user/adrian/if_ath_tx branch.
Legacy (ie, pre-AR5416) devices also use the per-software
TXQ support and (in theory) can support non-aggregation
ADDBA sessions. However, the net80211 stack doesn't currently
support this.
In summary:
TX path:
* queued frames normally go onto a per-TID, per-node queue
* some special frames (eg ADDBA control frames) are thrown
directly onto the relevant hardware queue so they can
go out before any software queued frames are queued.
* Add methods to create, suspend, resume and tear down an
aggregation session.
* Add in software retransmission of both normal and aggregate
frames.
* Add in completion handling of aggregate frames, including
parsing the block ack bitmap provided by the hardware.
* Write an aggregation function which can assemble frames into
an aggregate based on the selected rate control and channel
configuration.
* The per-TID queues are locked based on their target hardware
TX queue. This matches what ath9k/atheros does, and thus
simplified porting over some of the aggregation logic.
* When doing TX aggregation, stick the sequence number allocation
in the TX path rather than net80211 TX path, and protect it
by the TXQ lock.
Rate control:
* Delay rate control selection until the frame is about to
be queued to the hardware, so retried frames can have their
rate control choices changed. Frames with a static rate
control selection have that applied before each TX, just
to simplify the TX path (ie, not have "static" and "dynamic"
rate control special cased.)
* Teach ath_rate_sample about aggregates - both completion and
errors.
* Add an EWMA for tracking what the current "good" MCS rate is
based on failure rates.
Misc:
* Introduce a bunch of dirty hacks and workarounds so TID mapping
and net80211 frame inspection can be kept out of the net80211
layer. Because of the way this code works (and it's from Atheros
and Linux ath9k), there is a consistent, 1:1 mapping between
TID and AC. So we need to ensure that frames going to a specific
TID will _always_ end up on the right AC, and vice versa, or the
completion/locking will simply get very confused. I plan on
addressing this mess in the future.
Known issues:
* There is no BAR frame transmission just yet. A whole lot of
tidying up needs to occur before BAR frame TX can occur in the
"correct" place - ie, once the TID TX queue has been drained.
* Interface reset/purge/etc results in frames in the TX and RX
queues being removed. This creates holes in the sequence numbers
being assigned and the TX/RX AMPDU code (on either side) just
hangs.
* There's no filtered frame support at the present moment, so
stations going into power saving mode will simply have a number
of frames dropped - likely resulting in a traffic "hang".
* Raw frame TX is going to just not function with 11n aggregation.
Likely this needs to be modified to always override the sequence
number if the frame is going into an aggregation session.
However, general raw frame injection currently doesn't work in
general in net80211, so let's just ignore this for now until
this is sorted out.
* HT protection is just not implemented and won't be until the above
is sorted out. In addition, the AR5416 has issues RTS protecting
large aggregates (anything >8k), so the work around needs to be
ported and tested. Thus, this will be put on hold until the above
work is complete.
* The rate control module 'sample' is the only currently supported
module; onoe/amrr haven't been tested and have likely bit rotted
a little. I'll follow up with some commits to make them work again
for non-11n rates, but they won't be updated to handle 11n and
aggregation. If someone wishes to do so then they're welcome to
send along patches.
* .. and "sample" doesn't really do a good job of 11n TX. Specifically,
the metrics used (packet TX time and failure/success rates) isn't as
useful for 11n. It's likely that it should be extended to take into
account the aggregate throughput possible and then choose a rate
which maximises that. Ie, it may be acceptable for a higher MCS rate
with a higher failure to be used if it gives a more acceptable
throughput/latency then a lower MCS rate @ a lower error rate.
Again, patches will be gratefully accepted.
Because of this, ATH_ENABLE_11N is still not enabled by default.
Sponsored by: Hobnob, Inc.
Obtained from: Linux, Atheros
preparation for TX aggregation.
* Add in logic which calls ath_buf bf->bf_comp if it's set.
This allows for AMPDU (and RIFS, and FF, if someone desires) code
to handle completion - which includes freeing subframes, retransmitting
subframes, etc.
* Break out the buffer free, buffer busy/unbusy default completion handler
code into separate functions. This allows bf_comp methods to free and
unbusy each subframe ath_buf as required.
* Break out the statistics update code into a separate function, just
to clean up the TX completion path a little.
Sponsored by: Hobnob, Inc.
* Immediately return NULL if a buffer isn't available;
* Track the "buffers not available" count;
* Clear some fields used for tx aggregation;
* Add ath_buf_clone() which clones the majority of buffer state.
This is needed when retransmission of a "busy" buffer is required.
Sponsored by: Hobnob, Inc.
and interface resets to be marked as ATH_RESET_DEFAULT, ATH_RESET_FULL,
ATH_RESET_NOLOSS.
Currently a reset is still a reset - ie, all tx/rx frames in the hardware
queues are purged. This means that those frames will be lost to the 11n TX
and RX aggregation state tracking, breaking AMPDU sessions.
The (eventual) new semantics:
* ATH_RESET_DEFAULT:
full reset, this is the default for reset situations
which I haven't yet figured out what they should be.
* ATH_RESET_FULL:
A full reset - for things such as channel changes.
* ATH_RESET_NOLOSS:
Don't flush TX/RX queues - handle pending RX frames and leave TX
frames where they are; restart TX DMA from where it was.
There's two reasons for this:
* the raw and non-raw TX path shares a lot of duplicate code which should be
refactored;
* the 11n-ready chip TX path needs a little reworking.
