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Date:   Tue, 10 Jan 2023 10:49:46 +0530
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Subject: Re: [PATCH] wifi: ath11k: Optimize 6 GHz scan time
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To:     James Prestwood <prestwoj@gmail.com>,
        Marcel Holtmann <marcel@holtmann.org>
CC:     <ath11k@lists.infradead.org>, <linux-wireless@vger.kernel.org>
References: <20221220043823.20382-1-quic_mpubbise@quicinc.com>
 <5DAEA8B2-2B44-4A91-9E57-12B6C6B6C1FC@holtmann.org>
 <2861463e-a097-7efe-bc75-f13c8faf9547@quicinc.com>
 <378a1d63b3752ace7384c44d6f5184753fa7795d.camel@gmail.com>
From:   Manikanta Pubbisetty <quic_mpubbise@quicinc.com>
In-Reply-To: <378a1d63b3752ace7384c44d6f5184753fa7795d.camel@gmail.com>
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On 12/29/2022 2:52 AM, James Prestwood wrote:
> Hi Manikanta,
>> By the way, userspace itself selects the frequencies to scan, not the
>> driver.
>>
>> If we see the split scan implementation in cfg80211, this is the how
>> it
>> is implemented. If NL80211_SCAN_FLAG_COLOCATED_6GHZ is set, it
>> selects
>> all PSC channels and those non-PSC channels where RNR IE information
>> is
>> found in the legacy scan results. If this flag is not set, all
>> channels
>> in 6 GHz are included in the scan freq list. It is upto userspace to
>> decide what it wants.
> 
> 
> This isn't your problem, but it needs to be said:
> 
> The nl80211 docs need and update to reflect this behavior (or remove
> the PSC logic). IMO this is really weird that the kernel selects PSC's
> based on the co-located flag. The docs don't describe this behavior and
> the flag's name is misleading (its not
> SCAN_FLAG_COLOCATED_AND_PSC_6GHZ) :)
>

Sorry for the late reply, I was on vacation.

What you said make sense. The existing flag should not add PSC channels 
according to the flag description.

We can add another flag something like you pointed out 
SCAN_FLAG_COLOCATED_AND_PSC_6GHZ and include PSC channels if this flag 
is set. What do you say?

> If userspace doesn't specify a channel list then the kernel can do
> whatever it wants, but otherwise it should stick to the requested
> channels and scan only for co-located APs if the flag was set, not
> PSC's too.
> 
> This basically adds ~3x the time to IWD's quick scan's for 6GHz capable
> cards regardless if there are any co-located AP's. ugh.

True.

Thanks,
Manikanta