From mboxrd@z Thu Jan  1 00:00:00 1970
From: Robert Meschke <r_meschke@yahoo.de>
Date: Mon, 13 Sep 2010 18:30:57 +0200
Subject: [ath9k-devel] Antenna Configuration
References: 4C8E49AF.7050507@yahoo.de
Message-ID: <4C8E51C1.4010803@yahoo.de>
List-Id: <ath9k-devel.lists.ath9k.org>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
To: ath9k-devel@lists.ath9k.org

  Hi Adrian,

look at the main.c of ath9k.

/*
  * Update tx/rx chainmask. For legacy association,
  * hard code chainmask to 1x1, for 11n association, use
  * the chainmask configuration, for bt coexistence, use
  * the chainmask configuration even in legacy mode.
  */
void ath_update_chainmask(struct ath_softc *sc, int is_ht)
{
     struct ath_hw *ah = sc->sc_ah;
     struct ath_common *common = ath9k_hw_common(ah);

     if ((sc->sc_flags & SC_OP_SCANNING) || is_ht ||
         (ah->btcoex_hw.scheme != ATH_BTCOEX_CFG_NONE)) {
         common->tx_chainmask = ah->caps.tx_chainmask;
         common->rx_chainmask = ah->caps.rx_chainmask;
     } else {
         common->tx_chainmask = 1;
         common->rx_chainmask = 1;
     }

     ath_print(common, ATH_DBG_CONFIG,
           "tx chmask: %d, rx chmask: %d\n",
           common->tx_chainmask,
           common->rx_chainmask);
}

This function is called on every channel change. If there is no 11n mode 
1x1 is used (when no bt coexistence is used)   -> always chain0 is used. 
So i think that antenna diversity is impossible in legacy mode!? with no 
bt coexictence.  I don't know the term bt coexistence (Bluetooth - 
coexictence!?)
My patch only overides the capability field. I don't touch this 
function. So I think my patch can only work well in 11n mode.

Btw. If you setup 2x2 on AR9160 you will use chain0 an chain1. I got 
strange behaviour, when I tried to use for example chain 0 and chain2

Robert