Message-ID: <f0dcee96-3509-01db-2c24-f38183f1e314@quicinc.com>
Date:   Thu, 9 Mar 2023 15:13:57 +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
Content-Language: en-US
From:   Manikanta Pubbisetty <quic_mpubbise@quicinc.com>
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>
 <7ddf99b1-4aef-c950-f61b-ba79ed086095@quicinc.com>
In-Reply-To: <7ddf99b1-4aef-c950-f61b-ba79ed086095@quicinc.com>
Content-Type: text/plain; charset="UTF-8"; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 2/27/2023 9:53 AM, Manikanta Pubbisetty wrote:
> 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.
> 

Sent out a patch to update the documentation for review.
https://patchwork.kernel.org/project/linux-wireless/patch/20230308104556.9399-1-quic_mpubbise@quicinc.com/

Thanks,
Manikanta