[rt2x00-users] rt2800: missing parts for 11n support

Ivo Van Doorn ivdoorn at gmail.com
Fri May 7 21:53:33 AEST 2010

On Fri, May 7, 2010 at 1:51 PM, Helmut Schaa
<helmut.schaa at googlemail.com> wrote:
> Hi,
> Am Freitag 07 Mai 2010 schrieb Ivo Van Doorn:
>> > using 11n MCS rates works already fine with the rt2800 devices when hardcoded
>> > in the tx descriptor ;) as far as I could see also reception of MCS rates works
>> > fine as long as HT20 is used.
>> Even for receiving?
> I'm pretty sure I saw this, yes. I guess there is something wrong in the
> way we set up the receiver for HT40.
>> > Did I miss anything here or is it really only this one bit missing to get
>> > 11n support?
>> Aggregation support is missing, both on the receiving as sending side.
>> That is one of the most important things which must be implemented for
>> full 11n support. I believe the receiving side must be implemented to fix
>> some loss of RX frames. The hardware seems to receive multiple frames
>> in one block, as-if it was aggregated for some regular frames as well. This
>> was at least reported some months ago by somebody.
> Hmm, AFAIK mac80211 handles all of the MAC layer stuff like negotiating ba
> sessions and will tell us about the results via ampdu_action. So, I'm not
> sure if we have to implement a lot or if we only have to set a few registers
> up for aggregation. Hopefully the second approach is enough ;)

Negotiating stuff is indeed for mac80211. But we assume only one frame is
placed in the RX entry. Which is not the case. There can be multiple, each
with its own RX descriptor. So we have to parse that correctly.

AFAIK for sending we have the same issue, we need to give each frame
in the aggregated
frame its own TX descriptor.


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