Re: [PATCH 3.14] ath9k: fix ps-poll responses under a-mpdu sessions

[Felix Fietkau <nbd@openwrt.org>]

On 2014-03-11 15:22, Helmut Schaa wrote:
> On Tue, Mar 11, 2014 at 10:36 AM, Felix Fietkau <nbd@openwrt.org> wrote:
>> On 2014-03-11 10:28, Helmut Schaa wrote:
>>> On Sat, Feb 22, 2014 at 1:48 PM, Felix Fietkau <nbd@openwrt.org> wrote:
>>>> When passing tx frames to the U-APSD queue for powersave poll responses,
>>>> the ath_atx_tid pointer needs to be passed to ath_tx_setup_buffer for
>>>> proper sequence number accounting.
>>>>
>>>> This fixes high latency and connection stability issues with ath9k
>>>> running as AP and a few kinds of mobile phones as client, when PS-Poll
>>>> is heavily used
>>>>
>>>> Cc: stable@vger.kernel.org
>>>> Signed-off-by: Felix Fietkau <nbd@openwrt.org>
>>>> ---
>>>
>>> Hi Felix,
>>>
>>> this commit introduced a regression for me when using Intel Win7
>>> clients on a ath9k AP.
>>>
>>> I was not able to track the exact issue down yet :( but it seems to be
>>> related to the Intel
>>> client constantly tearing down the BA session and entering/leaving PS mode.
>>>
>>> Any idea?
>> Please make some packet captures and describe more clearly what the
>> regression is. Do you see connections stalling, big latencies, etc?
> 
> From what I can see with this patch action frames (like ADDBA and DELBA) get
> sequence numbers from TID 0 assigned instead of a seq number from the global
> counter. And that seems to "confuse" the client.
> 
> The following patch solves the issue for me and seems to still keep
> Felix original intention ...
Looks good to me, also because it ensures that action/mgmt frames are
sent out faster, even with filled data queues.
To really make sure that this issue does not happen again, we should
also have a check in ath_tx_setup_buffer where it actually assigns the
seqno.
This will become useful in case we need to buffer non-data packets (e.g.
for things like P2P powersave).

- Felix