Return-path: Received: from nbd.name ([46.4.11.11]:55273 "EHLO nbd.name" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752931Ab1KJKFG (ORCPT ); Thu, 10 Nov 2011 05:05:06 -0500 Message-ID: <4EBBA1C4.3070007@openwrt.org> (sfid-20111110_110510_958975_A2EE1731) Date: Thu, 10 Nov 2011 11:04:52 +0100 From: Felix Fietkau MIME-Version: 1.0 To: Rajkumar Manoharan CC: linville@tuxdriver.com, linux-wireless@vger.kernel.org, Paul Stewart , Adrian Chadd Subject: Re: [PATCH v2 4/4] ath9k_hw: Fix tx power settings for AR9003 References: <1320918297-1799-1-git-send-email-rmanohar@qca.qualcomm.com> In-Reply-To: <1320918297-1799-1-git-send-email-rmanohar@qca.qualcomm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-wireless-owner@vger.kernel.org List-ID: On 2011-11-10 10:44 AM, Rajkumar Manoharan wrote: > Retriving tx power for 2x2 and 3x3 chainmask is not handled > properly. While calculating tx power for 2x2, 3 dBm was reduced > and for 3x3, 5 dBm was reduced which should be added back when > retriving. > > Cc: Paul Stewart > Signed-off-by: Rajkumar Manoharan I think the tx power reduction for 2x2/3x3 needs to be revisited. In the discussion that led to Walsh spatial spreading being disabled you mentioned this: > In 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) So if I understand this issue correctly, Walsh spatial spreading was disabled so that the tx power for 2x2 or 3x3 would not have to be reduced by the array gain contribution - yet we're still doing that. When Adrian pointed out that tx power is reduced based on the number of chains, you mentioned this: > Those pwrdecrease fields are applicable for AR9280 chips not for AR9003. According to this patch, this doesn't seem to match what the code does, though I didn't notice it back then. So before we merge this patch, let's decide whether we actually need this tx power reduction or not. - Felix