Message-ID: <7ddf99b1-4aef-c950-f61b-ba79ed086095@quicinc.com>
Date:   Mon, 27 Feb 2023 09:53:43 +0530
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101
 Thunderbird/102.6.1
Subject: Re: [PATCH] wifi: ath11k: Optimize 6 GHz scan time
To:     Johannes Berg <johannes@sipsolutions.net>,
        James Prestwood <prestwoj@gmail.com>,
        Marcel Holtmann <marcel@holtmann.org>
CC:     <ath11k@lists.infradead.org>, <linux-wireless@vger.kernel.org>,
        <ilan.peer@intel.com>
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>
 <0b06dea9-d5be-1edc-62ca-576398d1bcd8@quicinc.com>
 <0e7644cbfa9e4ba0d534681166ca467ea1684719.camel@gmail.com>
 <10e4b6bf-f375-e50f-063a-b44471359d25@quicinc.com>
 <56a3651e48ae621afa4c50f1ba0d9fedeefb2c31.camel@sipsolutions.net>
Content-Language: en-US
From:   Manikanta Pubbisetty <quic_mpubbise@quicinc.com>
In-Reply-To: <56a3651e48ae621afa4c50f1ba0d9fedeefb2c31.camel@sipsolutions.net>
Content-Type: text/plain; charset="UTF-8"; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 2/24/2023 3:45 PM, Johannes Berg wrote:
> On Fri, 2023-02-24 at 15:38 +0530, Manikanta Pubbisetty wrote:
>> On 1/10/2023 10:35 PM, James Prestwood wrote:
>>> On Tue, 2023-01-10 at 10:49 +0530, Manikanta Pubbisetty wrote:
>>>> 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?
>>>
>>> I'm no authority here, just wanted to point this out. This is something
>>> that would need to be in mac80211 though, not just a specific driver.
>>> It would be up to the maintainers and would require changing the
>>> behavior of the existing flag, which then changes behavior in
>>> wpa_supplicant/hostapd. So its somewhat intrusive.
>>>
>>> But personally I'd be for it. And just require userspace include PSC's
>>> like any other channels if they need those.
>>>
>>
>> Hi Johannes,
>>
>> What is your opinion on the changes being proposed to the 6 GHz scan in
>> cfg80211 that is being discussed in this thread?
>>
> 
> I don't think we can/should change the semantics of an existing flag
> now, but we can certainly update the documentation to match the
> implementation, and add more flags to make it more flexible.
> 
> johannes

Sure, makes sense. I'll make the changes and send them out for review.

Thanks,
Manikanta