Subject: Re: [PATCH 08/11] mt76x02u: implement pre TBTT work for USB
To:     Stanislaw Gruszka <sgruszka@redhat.com>
Cc:     linux-wireless@vger.kernel.org,
        Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
References: <1551692896-7062-1-git-send-email-sgruszka@redhat.com>
 <1551692896-7062-9-git-send-email-sgruszka@redhat.com>
 <5844c0b8-3db9-d985-da75-a11318df37c5@nbd.name>
 <20190318095014.GA3323@redhat.com>
From:   Felix Fietkau <nbd@nbd.name>
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Date:   Mon, 18 Mar 2019 10:57:47 +0100
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On 2019-03-18 10:50, Stanislaw Gruszka wrote:
> On Sat, Mar 16, 2019 at 08:44:21PM +0100, Felix Fietkau wrote:
>> On 2019-03-04 10:48, Stanislaw Gruszka wrote:
>> > Program beacons data and PS buffered frames on TBTT work for USB.
>> > We do not have MT_TXQ_PSD queue available via USB endpoints. The way
>> > we can send PS broadcast frames in timely manner before PS stations go
>> > sleep again is program them in beacon data area. Hardware do not modify
>> > those frames since TXWI is properly configured. mt76x02_mac_set_beacon()
>> > already handle this and free no longer used frames.
>> > 
>> > Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
>> I think it's a nice idea, but there is one problem with that approach:
>> beacon slots only have 1024 bytes for TXWI + data.
>> I think to support this properly, you probably need to adjust beacon
>> offsets for USB dynamically and limit the number of frames to what you
>> can fit in SRAM.
> That would be good since we could sent more buffered frames (ARP frames
> are small), but for now I would prefer simpler solution to enable 
> AP support for USB: increase slot size to 1600 and make only 5 slots
> available.
Then you should probably limit the number of AP interfaces for USB as
well. Otherwise, people are going to do crazy things like bring up 4
virtual AP interfaces and expect multicast to work :)

- Felix