Re: [PATCH v3 11/13] ath9k_hw: Disable Walsh spatial spreading for 2 chains

[Rajkumar Manoharan <rmanohar@qca.qualcomm.com>]

On Fri, Aug 05, 2011 at 08:24:53AM +0530, Rajkumar Manoharan wrote:
> On Thu, Aug 04, 2011 at 08:23:28PM +0200, Felix Fietkau wrote:
> > On 2011-08-04 7:54 PM, Rajkumar Manoharan wrote:
> > >The Walsh bit is disabled for regulatory consideration.
> > >
> > >As per the FCC rulings, only transmissions that are completely
> > >non-coherent, are allowed to waive the array gain contribution
> > >to EIRP for multi-transmit configurations. The use of 2-stream
> > >with 2 transmit and use of 3-steam with 3 transmit qualifies
> > >for this spatial multiplexing MIMO classification as long as
> > >the streams are directly mapped to each radio (not Walsh spread
> > >prior to splitting to multiple radios)
> > I think ath9k does not waive the array gain contribution. I haven't
> > checked AR9003, but on AR9002 and older, it explicitly includes the
> > array gain contribution in the tx power limit calculation. I'm not
> > sure that unconditionally disabling spatial spreading is the right
> > way to deal with this.
> >
> We might violate the FCC rule with 2x2 config(3dB higher at 2-stream)
> if this bit is enabled. Based on chainmask we can disable Walsh bit.

This change does not affect 3x3, since we don't use 2-chain for 2-stream.
And Walsh mode would follow INI setting for 2x2 or 3x3 config.

--
Rajkumar