Re: [PATCHv2] ipw2200: fix scanning while associated

[Zhu Yi <yi.zhu@intel.com>]

On Wed, 2008-12-10 at 05:17 -0700, Helmut Schaa wrote:
> This patch fixes sporadic firmware restarts when scanning while associated.
> 
> The firmware will quietly cancel a scan (while associated) if the dwell time
> for a channel to be scanned is larger than the time it may stay away from the
> operating channel (because of DTIM catching). Unfortunately the driver is not
> notified about the canceled scan and therefore the scan watchdog timeout will
> be hit and the driver causes a firmware restart which results in
> disassociation. This mainly happens on passive channels which use a dwell time
> of 120 whereas a typical beacon interval is around 100.
> 
> The patch changes the dwell time for passive channels to be slightly smaller
> than the actual beacon interval to work around the firmware issue. Furthermore
> the number of allowed beacon misses is increased from one to three as otherwise
> most scans (while associated) won't complete successfully.
> 
> However scanning while associated will still fail in corner cases such as a
> beacon intervals below 30.
> 
> Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>

Acked-by: Zhu Yi <yi.zhu@intel.com>

Thanks,
-yi

> ---
> 
> diff --git a/drivers/net/wireless/ipw2x00/ipw2200.c b/drivers/net/wireless/ipw2x00/ipw2200.c
> index dc6eb49..8e7affa 100644
> --- a/drivers/net/wireless/ipw2x00/ipw2200.c
> +++ b/drivers/net/wireless/ipw2x00/ipw2200.c
> @@ -4347,7 +4347,8 @@ static void ipw_handle_missed_beacon(struct ipw_priv *priv,
>  		return;
>  	}
>  
> -	if (priv->status & STATUS_SCANNING) {
> +	if (priv->status & STATUS_SCANNING &&
> +	    missed_count > IPW_MB_SCAN_CANCEL_THRESHOLD) {
>  		/* Stop scan to keep fw from getting
>  		 * stuck (only if we aren't roaming --
>  		 * otherwise we'll never scan more than 2 or 3
> @@ -6282,6 +6283,20 @@ static void ipw_add_scan_channels(struct ipw_priv *priv,
>  	}
>  }
>  
> +static int ipw_passive_dwell_time(struct ipw_priv *priv)
> +{
> +	/* staying on passive channels longer than the DTIM interval during a
> +	 * scan, while associated, causes the firmware to cancel the scan
> +	 * without notification. Hence, don't stay on passive channels longer
> +	 * than the beacon interval.
> +	 */
> +	if (priv->status & STATUS_ASSOCIATED
> +	    && priv->assoc_network->beacon_interval > 10)
> +		return priv->assoc_network->beacon_interval - 10;
> +	else
> +		return 120;
> +}
> +
>  static int ipw_request_scan_helper(struct ipw_priv *priv, int type, int direct)
>  {
>  	struct ipw_scan_request_ext scan;
> @@ -6328,7 +6343,7 @@ static int ipw_request_scan_helper(struct ipw_priv *priv, int type, int direct)
>  	  	IPW_DEBUG_WX("use passive scanning\n");
>  	  	scan_type = IPW_SCAN_PASSIVE_FULL_DWELL_SCAN;
>  		scan.dwell_time[IPW_SCAN_PASSIVE_FULL_DWELL_SCAN] =
> -			cpu_to_le16(120);
> +			cpu_to_le16(ipw_passive_dwell_time(priv));
>  		ipw_add_scan_channels(priv, &scan, scan_type);
>  		goto send_request;
>  	}
> @@ -6344,7 +6359,8 @@ static int ipw_request_scan_helper(struct ipw_priv *priv, int type, int direct)
>  	scan.dwell_time[IPW_SCAN_ACTIVE_BROADCAST_AND_DIRECT_SCAN] =
>  		cpu_to_le16(20);
>  
> -  	scan.dwell_time[IPW_SCAN_PASSIVE_FULL_DWELL_SCAN] = cpu_to_le16(120);
> +  	scan.dwell_time[IPW_SCAN_PASSIVE_FULL_DWELL_SCAN] =
> +		cpu_to_le16(ipw_passive_dwell_time(priv));
>  	scan.dwell_time[IPW_SCAN_ACTIVE_DIRECT_SCAN] = cpu_to_le16(20);
>  
>  #ifdef CONFIG_IPW2200_MONITOR
> diff --git a/drivers/net/wireless/ipw2x00/ipw2200.h b/drivers/net/wireless/ipw2x00/ipw2200.h
> index 0a84d52..277b274 100644
> --- a/drivers/net/wireless/ipw2x00/ipw2200.h
> +++ b/drivers/net/wireless/ipw2x00/ipw2200.h
> @@ -245,6 +245,7 @@ enum connection_manager_assoc_states {
>  #define HOST_NOTIFICATION_S36_MEASUREMENT_REFUSED       31
>  
>  #define HOST_NOTIFICATION_STATUS_BEACON_MISSING         1
> +#define IPW_MB_SCAN_CANCEL_THRESHOLD                    3
>  #define IPW_MB_ROAMING_THRESHOLD_MIN                    1
>  #define IPW_MB_ROAMING_THRESHOLD_DEFAULT                8
>  #define IPW_MB_ROAMING_THRESHOLD_MAX                    30