From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mtiwmhc12.worldnet.att.net ([204.127.131.116]:49112 "EHLO mtiwmhc12.worldnet.att.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754704AbZAWDjg (ORCPT ); Thu, 22 Jan 2009 22:39:36 -0500 Message-ID: <49793BE7.3020509@lwfinger.net> (sfid-20090123_043941_213202_831B7915) Date: Thu, 22 Jan 2009 21:39:19 -0600 From: Larry Finger MIME-Version: 1.0 To: Felix Fietkau CC: wireless , =?ISO-8859-1?Q?Mart=EDn_?= =?ISO-8859-1?Q?Ernesto_Barreyro?= , Johannes Berg Subject: Re: Minstrel rate-setting question References: <496CE438.6020408@lwfinger.net> <496D2772.4060104@lwfinger.net> <496D3118.7060906@lwfinger.net> <496D665A.90608@lwfinger.net> <4972B1E7.7000005@lwfinger.net> <4977612D.7050500@lwfinger.net> <1232664643.4589.5.camel@note-tatin> <49790C43.5050100@lwfinger.net> <497929C1.9060804@openwrt.org> In-Reply-To: <497929C1.9060804@openwrt.org> Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-wireless-owner@vger.kernel.org List-ID: Felix Fietkau wrote: > I believe that it's not minstrel's fault. According to the information that > I have about RTL8187L, the chip implements rate fallback. If the chip changes > rates during retransmissions, the status information the way you gather it > will not be accurate and will trick minstrel into believing that higher rates > actually work (which in fact they don't). > Please do some transmissions at 54M and run a monitor mode capture on a different > card to see if it changes the rate during transmission and how frequently it > uses one rate before falling back (if indeed my theory is correct). > This information could be used to provide some more accurate feedback through > multi-rate retry status information. I believe you have the clue. There is a register named RATE_FALLBACK and a bit called RTL818X_RATE_FALLBACK_ENABLE. I'm testing a patch that leaves this bit unset. Thanks, Larry