Re: [RFC v2] mac80211: stop tx before doing hw config and rate update

From: Johannes Berg <johannes@sipsolutions.net>
To: Rajkumar Manoharan <rmanohar@qca.qualcomm.com>
Cc: linux-wireless@vger.kernel.org
Subject: Re: [RFC v2] mac80211: stop tx before doing hw config and rate update
Date: Mon, 29 Aug 2011 17:39:01 +0200	[thread overview]
Message-ID: <1314632341.8959.22.camel@jlt3.sipsolutions.net> (raw)
In-Reply-To: <1314617635-27936-1-git-send-email-rmanohar@qca.qualcomm.com>

On Mon, 2011-08-29 at 17:03 +0530, Rajkumar Manoharan wrote:
> The assumption is that during the hw config, transmission was
> already stopped by mac80211. But during channel type change,
> the mac80211 continue to transmit frames. The driver like ath9k
> does chip reset while doing channel set. This could leads to
> buffer overflow at driver side. And also after configuring the channel
> and before doing rate updation, the frames are continued to xmit
> with older rates. This patch ensures that the frames are always
> xmitted with updated rates and avoid buffer overflow.
> 
> Signed-off-by: Rajkumar Manoharan <rmanohar@qca.qualcomm.com>
> ---
> v2: Removed new stop queue reason code by netif

why did you do that?

> +	netif_tx_stop_all_queues(sdata->dev);
> +
> +	drv_flush(local, false);
>  	/* channel_type change automatically detected */
>  	ieee80211_hw_config(local, 0);

it seems to me that if the driver queues were full & stopped, this
happens, then flush will clear the queues & start them, and you'll start
queues during flush again...

johannes