From: "Singh, Naveen" <navesing@qca.qualcomm.com>
To: "Chadd, Adrian" <achadd@qca.qualcomm.com>,
	"Valo, Kalle" <kvalo@qca.qualcomm.com>,
	"Pedersen, Thomas" <c_tpeder@qca.qualcomm.com>
CC: Luciano Coelho <coelho@ti.com>,
	Johannes Berg <johannes@sipsolutions.net>,
	ath6kl-devel <ath6kl-devel@qualcomm.com>,
	"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
	"victorg@ti.com" <victorg@ti.com>
Subject: RE: [PATCH] nl80211: specify RSSI threshold when scanning
Date: Thu, 14 Jun 2012 21:18:12 +0000
Message-ID: <43ED1A9ABC336248B5D371B7C9CCFB96016F347E@nasanexd02b.na.qualcomm.com> (sfid-20120614_231818_988457_0B5C2DFD)
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May not be possible to do in any platform you listed. I could be wrong here but from SW perspective if we decide to do following, it may be feasible:

1. We break down a single scan into multiple scan commands. Each scan just scanning one channel or a set of few channels. 
2. FW at least as 4 to 6 Kbytes of memory kept for scan results. 

But then there will not be much time left b/w for host to go to sleep.

Regards
Naveen Singh

-----Original Message-----
From: Chadd, Adrian 
Sent: Thursday, June 14, 2012 1:41 PM
To: Singh, Naveen; Valo, Kalle; Pedersen, Thomas
Cc: Luciano Coelho; Johannes Berg; ath6kl-devel; linux-wireless@vger.kernel.org; victorg@ti.com
Subject: RE: [PATCH] nl80211: specify RSSI threshold when scanning

Right. What platforms would this be more doable on? Mckinley? Peregrine?


Adrian

-----Original Message-----
From: Singh, Naveen
Sent: Thursday, June 14, 2012 1:21 PM
To: Chadd, Adrian; Valo, Kalle; Pedersen, Thomas
Cc: Luciano Coelho; Johannes Berg; ath6kl-devel; linux-wireless@vger.kernel.org; victorg@ti.com
Subject: RE: [PATCH] nl80211: specify RSSI threshold when scanning

Fw memory is generally very limited. Maintaining the complete scan results is almost next to impossible. There are also other implications like taking care of duplicates, in case of similar taking the one with higher signal strength, for same AP taking care of size differences b/w probe response and beacon etc. 

Passing the results as you receive avoids lot of these complications.

Regards
Naveen

-----Original Message-----
From: Chadd, Adrian
Sent: Thursday, June 14, 2012 12:40 PM
To: Valo, Kalle; Pedersen, Thomas
Cc: Luciano Coelho; Johannes Berg; ath6kl-devel; linux-wireless@vger.kernel.org; victorg@ti.com
Subject: RE: [PATCH] nl80211: specify RSSI threshold when scanning

Why then doesn't the host just stay asleep and let the firmware aggregate some scan results, and then fire those up in one message, waking the host up only once?


Adrian

-----Original Message-----
From: Valo, Kalle
Sent: Wednesday, June 13, 2012 11:29 PM
To: Pedersen, Thomas
Cc: Luciano Coelho; Johannes Berg; ath6kl-devel; linux-wireless@vger.kernel.org; victorg@ti.com
Subject: Re: [PATCH] nl80211: specify RSSI threshold when scanning

On 06/13/2012 11:50 PM, Pedersen, Thomas wrote:
> On Wed, Jun 13, 2012 at 02:56:26PM +0300, Kalle Valo wrote:
>
>> Funnily enough I don't have any idea how ath6kl has implemented this 
>> feature, but in theory this feature is useful also for the current 
>> normal scan (when the firmware/hardware supports it) as we can avoid 
>> host wakeups. If there are 10 APs, but all are below the RSSI 
>> threshold, we will have only 1 host wakeup (scan ready event) opposed 
>> to 11 wakeups
>> (10 AP found events plus 1 scan ready event).
> 
> But can the host even sleep on normal scans?

It's "implementation defined", the good ones can and bad ones can't :)

But from our (wireless developer) perspective we don't need to care about that, our job is to minimise all possible host wakeup events (timers, interrupts etc) as much as possible. That will allow the host to sleep more.

Kalle