I couldn't think of a way to maintain the hardware TXQ locks _and_ layer
on top of that per-TXQ software queuing and any other kind of fine-grained
locks (eg per-TID, or per-node locks.)
So for now, to facilitate some further code refactoring and development
as part of the final push to get software queue ps-poll and u-apsd handling
into this driver, just do away with them entirely.
I may eventually bring them back at some point, when it looks slightly more
architectually cleaner to do so. But as it stands at the present, it's
not really buying us much:
* in order to properly serialise things and not get bitten by scheduling
and locking interactions with things higher up in the stack, we need to
wrap the whole TX path in a long held lock. Otherwise we can end up
being pre-empted during frame handling, resulting in some out of order
frame handling between sequence number allocation and encryption handling
(ie, the seqno and the CCMP IV get out of sequence);
* .. so whilst that's the case, holding the lock for that long means that
we're acquiring and releasing the TXQ lock _inside_ that context;
* And we also acquire it per-frame during frame completion, but we currently
can't hold the lock for the duration of the TX completion as we need
to call net80211 layer things with the locks _unheld_ to avoid LOR.
* .. the other places were grab that lock are reset/flush, which don't happen
often.
My eventual aim is to change the TX path so all rejected frame transmissions
and all frame completions result in any ieee80211_free_node() calls to occur
outside of the TX lock; then I can cut back on the amount of locking that
goes on here.
There may be some LORs that occur when ieee80211_free_node() is called when
the TX queue path fails; I'll begin to address these in follow-up commits.
of small (< 256 byte) aggregate frames.
This needs to be done or 11n aggregation TX just simply doesn't work
on these NICs.
Whilst here, extend some debug printing; I was using this whilst
debugging the TX power setup in the TX descriptor(s) on the AR9380.
the ATH_TXQ_* macros.
* Introduce the new macros;
* rename the TID queue and TID filtered frame queue so the compiler
tells me I'm using the wrong macro.
These should correspond 1:1 to the existing code.
This had the side effect of clearing HAL_TXDESC_CLRDMASK for a bunch of
frames, meaning they'd end up being potentially filtered if there were
an error. This is fine in the previous world as they'd just be
software retried but now that I'm working on filtered frames, these
descriptors would be endlessly retried until another valid frame would
come along that had CLRDMASK set.
code is called and remove it from ath_buf_set_rate().
For the legacy (non-11n API) TX routines, ath_hal_filltxdesc() takes care
of setting up the intermediary and final descriptors right, complete
with copying the rate control info into the final descriptor so the
rate modules can grab it.
The 11n version doesn't do this - ath_hal_chaintxdesc() doesn't
copy the rate control bits over, nor does it clear isaggr/moreaggr/
pad delimiters. So the call to setuplasttxdesc() is needed here.
So:
* legacy NICs - never call the 11n rate control stuff, so filltxdesc
copies the rate control info right;
* 11n NICs transmitting legacy or 11n non-aggregate frames -
ath_hal_set11nratescenario() is called to setup rate control and
then ath_hal_filltxdesc() chains them together - so the rate control
info is right;
* 11n aggregate frames - set11nratescenario() is called, then
ath_hal_chaintxdesc() is called to chain a list of aggregate and subframes
together. This requires a call to ath_hal_setuplasttxdesc() to complete
things.
Tested:
* AR9280 in station mode
TODO:
* I really should make sure that the descriptor contents get blanked
out correctly or garbage left over from aggregate frames may show
up in non-aggregate frames, leading to badness.
(future) TPC support in the AR9300 HAL.
This is effectively a no-op for the moment as (a) TPC isn't really
supported, (b) the AR9300 HAL isn't yet public, and (c) the existing
HAL code doesn't use these fields.
Obtained from: Qualcomm Atheros
* Introduce TX DMA setup/teardown methods, mirroring what's done in
the RX path.
Although the TX DMA descriptor is setup via ath_desc_alloc() /
ath_desc_free(), there TX status descriptor ring will be allocated
in this path.
* Remove some of the TX EDMA capability probing from the RX path and
push it into the new TX EDMA path.
* Use ATH_RC_NUM instead of '4' when iterating over the ratecontrol series
array.
* A few style(9) fixes, hopefully no regressions here.
* Add some comments that better describe what's going on.
This showed up when doing heavy UDP throughput on SMP machines.
The problem with this is because the 802.11 sequence number is being
allocated separately to the CCMP PN replay number (which is assigned
during ieee80211_crypto_encap()).
Under significant throughput (200+ MBps) the TX path would be stressed
enough that frame TX/retry would force sequence number and PN allocation
to be out of order. So once the frames were reordered via 802.11 seqnos,
the CCMP PN would be far out of order, causing most frames to be discarded
by the receiver.
I've fixed this in some local work by being forced to:
(a) deal with the issues that lead to the parallel TX causing out of
order sequence numbers in the first place;
(b) fix all the packet queuing issues which lead to strange (but mostly
valid) TX.
I'll begin fixing these in a subsequent commit or five.
PR: kern/166190
if any subframes in an aggregate have different protection from the
first frame in the formed aggregate, don't add that frame to the
aggregate.
This is likely a suboptimal method (I think we'll mostly be OK marking
frames that have seqno's with the same protection as normal data frames)
but I'll just be cautious for now.
within the BAW.
This regression was introduced in ane earlier commit by me to fix the
BAW seqno allocation-but-not-insertion-into-BAW race. Since it was only
ever using the to-be allocated sequence number, any frame retries
with the first frame in the BAW still in the software queue would
have constantly failed, as ni_txseqs[tid] would always be outside
the BAW.
TODO:
* Extract out the mostly common code here in the agg and non-agg ADDBA
case and stuff it into a single function.
PR: kern/166357
is queued to the hardware.
Because multiple concurrent paths can execute ath_start(), multiple
concurrent paths can push frames into the software/hardware TX queue
and since preemption/interrupting can occur, there's the possibility
that a gap in time will occur between allocating the sequence number
and queuing it to the hardware.
Because of this, it's possible that a thread will have allocated a
sequence number and then be preempted by another thread doing the same.
If the second thread sneaks the frame into the BAW, the (earlier) sequence
number of the first frame will be now outside the BAW and will result
in the frame being constantly re-added to the tail of the queue.
There it will live until the sequence numbers cycle around again.
This also creates a hole in the RX BAW tracking which can also cause
issues.
This patch delays the sequence number allocation to occur only just before
the frame is going to be added to the BAW. I've been wanting to do this
anyway as part of a general code tidyup but I've not gotten around to it.
This fixes the PR.
However, it still makes it quite difficult to try and ensure in-order
queuing and dequeuing of frames. Since multiple copies of ath_start()
can be run at the same time (eg one TXing process thread, one TX completion
task/one RX task) the driver may end up having frames dequeued and pushed
into the hardware slightly/occasionally out of order.
And, to make matters more annoying, net80211 may have the same behaviour -
in the non-aggregation case, the TX code allocates sequence numbers
before it's thrown to the driver. I'll open another PR to investigate
this and potentially introduce some kind of final-pass TX serialisation
before frames are thrown to the hardware. It's also very likely worthwhile
adding some debugging code into ath(4) and net80211 to catch when/if this
does occur.
PR: kern/166190
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
hardware supports it.
Since ni->ni_htcap in hostap mode is what the remote end has advertised,
not what has been negotiated/decided, we need to check ourselves what
the current channel width is and what the hardware supports before
enabling short-GI.
It's important that short-GI isn't enabled when it isn't negotiated
and when the hardware doesn't support it (ie, short-gi for 20mhz channels
on any chip < AR9287.)
I've quickly verified this on the AR9285 in 11n mode.
the channel width is ni->ni_chw, which is set to the negotiated channel
width. ni->ni_htflags is the capability, rather than the negotiated
value.
Teach both the TX path and the sample rate module about this.
This seems to work fine for STA but not HT/20 AP mode.
Further discussion with net80211 people will need to take place
to ensure that the right flags are set based on the negotiated
capabilities of the remote peer, rather than whatever the local
parameters are.
Sending short-gi frames in 20mhz may work on some chips but
it certainly isn't supported on anything currently supported
by the HAL; and sending HT40 frames in HT20 mode just plain
won't work.
These flags are just plain wrong - they're the node flags from negotiation,
not the configured flags. I'll jump in later on and figure out exactly
what should be done to properly set these two flags when in both STA mode
(ie, what the AP says is possible and what's configured) and AP mode
(ie, where the AP has a configuration, but then negotiates what's possible
with each node, so per-node configuration can and will differ.)
This allows the 11n 2.4ghz/ht20 mode to associate (but perform poorly still)
and exchange MCS rates with atheros reference APs and a Cisco/Linksys
E3000 AP.
correctly:
* pass in whether to allow the hardware to override the duration field
in the main data frame (durupdate_en) - PS_POLL frames in particular
don't have the duration bit overriden;
* there's no rts/cts duration here; that's done elsehwere
The AR5416 and later TX descriptors have new fields for supporting
11n bits (eg 20/40mhz mode, short/long GI) and enabling/disabling
RTS/CTS protection per rate.
These functions will be responsible for initialising the TX descriptors
for the AR5416 and later chips for both HT and legacy frames.
Beacon frames will remain using the non-11n TX descriptor setup for now;
Linux ath9k does much the same.
Note that these functions aren't yet used anywhere; a few more framework
changes are needed before all of the right rate information is available
for TX.
