Return-path: Received: from charlotte.tuxdriver.com ([70.61.120.58]:51977 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751944Ab1HOSpW (ORCPT ); Mon, 15 Aug 2011 14:45:22 -0400 Date: Mon, 15 Aug 2011 11:39:44 -0700 From: "John W. Linville" To: Rajkumar Manoharan Cc: Felix Fietkau , linux-wireless@vger.kernel.org Subject: Re: [PATCH v2 11/13] ath9k_hw: Disable Walsh spatial spreading for 2 chains Message-ID: <20110815183944.GB4134@tuxdriver.com> (sfid-20110815_204525_732674_63ECBD73) References: <1311941300-2590-1-git-send-email-rmanohar@qca.qualcomm.com> <1311941300-2590-11-git-send-email-rmanohar@qca.qualcomm.com> <4E32AA85.1030204@openwrt.org> <20110802094610.GA1235@vmraj-lnx.users.atheros.com> <4E3834CC.8010001@openwrt.org> <20110804174519.GB26255@vmraj-lnx.users.atheros.com> <4E3ADD14.6030802@openwrt.org> <20110815075503.GA898@vmraj-lnx.users.atheros.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20110815075503.GA898@vmraj-lnx.users.atheros.com> Sender: linux-wireless-owner@vger.kernel.org List-ID: On Mon, Aug 15, 2011 at 01:25:04PM +0530, Rajkumar Manoharan wrote: > On Thu, Aug 04, 2011 at 07:55:32PM +0200, Felix Fietkau wrote: > > On 2011-08-04 7:45 PM, Rajkumar Manoharan wrote: > > >On Tue, Aug 02, 2011 at 07:33:00PM +0200, Felix Fietkau wrote: > > >> On 2011-08-02 11:46 AM, Rajkumar Manoharan wrote: > > >> >On Fri, Jul 29, 2011 at 02:41:41PM +0200, Felix Fietkau wrote: > > >> >> On 2011-07-29 2:08 PM, Rajkumar Manoharan wrote: > > >> >> >Signed-off-by: Rajkumar Manoharan > > >> >> >--- > > >> >> > .../net/wireless/ath/ath9k/ar9003_2p2_initvals.h | 2 +- > > >> >> > 1 files changed, 1 insertions(+), 1 deletions(-) > > >> >> > > > >> >> >diff --git a/drivers/net/wireless/ath/ath9k/ar9003_2p2_initvals.h b/drivers/net/wireless/ath/ath9k/ar9003_2p2_initvals.h > > >> >> >index 2339728..28b44b0 100644 > > >> >> >--- a/drivers/net/wireless/ath/ath9k/ar9003_2p2_initvals.h > > >> >> >+++ b/drivers/net/wireless/ath/ath9k/ar9003_2p2_initvals.h > > >> >> >@@ -636,7 +636,7 @@ static const u32 ar9300_2p2_baseband_postamble[][5] = { > > >> >> > {0x00009e44, 0x02321e27, 0x02321e27, 0x02291e27, 0x02291e27}, > > >> >> > {0x00009e48, 0x5030201a, 0x5030201a, 0x50302012, 0x50302012}, > > >> >> > {0x00009fc8, 0x0003f000, 0x0003f000, 0x0001a000, 0x0001a000}, > > >> >> >- {0x0000a204, 0x000037c0, 0x000037c4, 0x000037c4, 0x000037c0}, > > >> >> >+ {0x0000a204, 0x000036c0, 0x000036c4, 0x000036c4, 0x000036c0}, > > >> >> > {0x0000a208, 0x00000104, 0x00000104, 0x00000004, 0x00000004}, > > >> >> > {0x0000a22c, 0x01026a2f, 0x01026a2f, 0x01026a2f, 0x01026a2f}, > > >> >> > {0x0000a230, 0x0000000a, 0x00000014, 0x00000016, 0x0000000b}, > > >> >> That patch makes no sense, it disables Walsh spatial spreading in > > >> >> the initvals, but the driver still enables it in > > >> >> ar9003_hw_set_channel_regs. > > >> >> By the way, why should we disable Walsh spatial spreading? > > >> >> > > >> >The initval table is filled with default values recommended in register spec. > > >> >This patch does that. And these default value can be altered during chip bringup > > >> >based on chip family. > > >> OK, then the patch description should probably mention that this > > >> change has no effect and does not actually disable this feature in > > >> general, since the driver unconditionally enables it elsewhere. > > >> > > >Felix, > > > > > >The Walsh bit is disabled for regulatory consideration. > > > > > >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) > > > > > >And also Walsh has to be disabled in ar9003_hw_set_channel_regs. > > >Thanks for finding out. Will send followup patch. > > Wouldn't that only be relevant if the regdomain/country setting is a > > FCC one *and* the configured tx power is close to the limit? > > It seems to me that if either of those is not the case, it should be > > valid to keep walsh spatial spreading enabled. > > > Sorry for the delayed response. > FCC limit for walsh enable is lower than that for walsh disable. > So disabling walsh bit will NOT limit tx power/affect tx power > even in cases where we are not FCC limited (most client cards). > > If the Tx power is not FCC limited, then enabling/disabling walsh > bit will not affect Avg. EVM/overall performance in any visible manner. > When this is the case, I do not see a strong reason to have any channel > based logic to enable/disable walsh bit. The simplest solution would be > to change 1 bit in INI. > > John, > > Do you want me to rebase and send it again? > > -- > Rajkumar Yes, please. Thanks, John -- John W. Linville Someday the world will need a hero, and you linville@tuxdriver.com might be all we have. Be ready.