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Message-ID: <378a1d63b3752ace7384c44d6f5184753fa7795d.camel@gmail.com>
Subject: Re: [PATCH] wifi: ath11k: Optimize 6 GHz scan time
From:   James Prestwood <prestwoj@gmail.com>
To:     Manikanta Pubbisetty <quic_mpubbise@quicinc.com>,
        Marcel Holtmann <marcel@holtmann.org>
Cc:     ath11k@lists.infradead.org, linux-wireless@vger.kernel.org
Date:   Wed, 28 Dec 2022 13:22:14 -0800
In-Reply-To: <2861463e-a097-7efe-bc75-f13c8faf9547@quicinc.com>
References: <20221220043823.20382-1-quic_mpubbise@quicinc.com>
         <5DAEA8B2-2B44-4A91-9E57-12B6C6B6C1FC@holtmann.org>
         <2861463e-a097-7efe-bc75-f13c8faf9547@quicinc.com>
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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) :)

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.