Date: Thu, 2 Feb 2012 08:38:43 -0600
From: Seth Forshee <seth.forshee@canonical.com>
To: Felix Fietkau <nbd@openwrt.org>
Cc: linux-wireless@vger.kernel.org,
	"Luis R. Rodriguez" <mcgrof@qca.qualcomm.com>,
	Jouni Malinen <jouni@qca.qualcomm.com>,
	Vasanthakumar Thiagarajan <vthiagar@qca.qualcomm.com>,
	Senthil Balasubramanian <senthilb@qca.qualcomm.com>
Subject: Re: CTS timeout issue with AR9285
Message-ID: <20120202143843.GB24483@ubuntu-macmini> (sfid-20120202_153850_756742_4BFF3A71)
References: <20120202042521.GA20635@ubuntu-macmini>
 <4F2A830A.8000905@openwrt.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
In-Reply-To: <4F2A830A.8000905@openwrt.org>
Sender: linux-wireless-owner@vger.kernel.org

On Thu, Feb 02, 2012 at 01:35:22PM +0100, Felix Fietkau wrote:
> On 2012-02-02 5:25 AM, Seth Forshee wrote:
> > I recently updated a machine with AR9285 wireless from kernel version
> > 3.0 to 3.2 and saw that wireless had become slow and unreliable. It
> > seems that the problem is extremely frequent CTS timeouts, which began
> > happening with commit adb5066 (ath9k_hw: do not apply the 2.4 ghz ack
> > timeout workaround to cts). Restoring the CTS timeout to the value prior
> > to this commit on top of 3.2 gets performance back to what it was with
> > 3.0.
> > 
> > I don't have any other ath9k cards lying around, but various other cards
> > are working fine with this router. Any ideas what's wrong here?
> Please try this patch:
> 
> --- a/drivers/net/wireless/ath/ath9k/hw.c
> +++ b/drivers/net/wireless/ath/ath9k/hw.c
> @@ -1061,13 +1061,16 @@ void ath9k_hw_init_global_settings(struc
>  
>  	/*
>  	 * Workaround for early ACK timeouts, add an offset to match the
> -	 * initval's 64us ack timeout value.
> +	 * initval's 64us ack timeout value. Use 48us for the CTS timeout.
>  	 * This was initially only meant to work around an issue with delayed
>  	 * BA frames in some implementations, but it has been found to fix ACK
>  	 * timeout issues in other cases as well.
>  	 */
> -	if (conf->channel && conf->channel->band == IEEE80211_BAND_2GHZ)
> +	if (conf->channel && conf->channel->band == IEEE80211_BAND_2GHZ) {
>  		acktimeout += 64 - sifstime - ah->slottime;
> +		ctstimeout += 48 - sifstime - ah->slottime;
> +	}
> +
>  
>  	ath9k_hw_set_sifs_time(ah, sifstime);
>  	ath9k_hw_setslottime(ah, slottime);
> 

The wireless seems to be working fine with this patch.