From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from wolverine02.qualcomm.com ([199.106.114.251]:54371 "EHLO wolverine02.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752724Ab1HEHXx (ORCPT ); Fri, 5 Aug 2011 03:23:53 -0400 Date: Fri, 5 Aug 2011 12:54:12 +0530 From: Rajkumar Manoharan To: Adrian Chadd CC: Felix Fietkau , , Subject: Re: [PATCH v3 11/13] ath9k_hw: Disable Walsh spatial spreading for 2 chains Message-ID: <20110805072411.GA5510@vmraj-lnx.users.atheros.com> (sfid-20110805_092357_532163_AA6EFF08) References: <1312480447-27483-1-git-send-email-rmanohar@qca.qualcomm.com> <4E3AE3A0.2000308@openwrt.org> <20110805025452.GA28266@vmraj-lnx.users.atheros.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" In-Reply-To: Sender: linux-wireless-owner@vger.kernel.org List-ID: On Fri, Aug 05, 2011 at 02:35:44PM +0800, Adrian Chadd wrote: > There's already code in the driver that subtracts 3 and 5 dB from the > max TX power. > > Some NICs have value=0 for pwrdecrease2chain and pwrdecrease3chain; I > have a feeling the EEPROMs in those have been programmed assuming 2 or > 3 chain TX with the current setting (ie, AR_PHY_FC_WALSH in > AR_PHY_TURBO). If they've calibrated the EEPROM settings based on that > bit being set for 2 or 3 chain TX, you may find they're already doing > the "right" thing. Flipping that bit off (and unconditionally > subtracting TX power) may result in a lower TX power than regulatory? > Those pwrdecrease fields are applicable for AR9280 chips not for AR9003. > I do suggest that someone with the relevant test equipment do some > investigation into what the behaviour is of a variety of NICs. I'd > love to survey what's going on but I'd have to acquire access to a > spectrum analyser. > These changes were done based on our system team's comments. -- Rajkumar > > > Adrian > > On 5 August 2011 10:54, 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. > > Any comments? > > > > -- > > Rajkumar > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-wireless" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at  http://vger.kernel.org/majordomo-info.html > >