Re: [PATCH] scan: limit COLOCATED_6GHZ flag to 6ghz devices

[James Prestwood <prestwoj@gmail.com>]

Hi Keith,

On 1/3/24 6:57 AM, KeithG wrote:
> On Wed, Jan 3, 2024 at 6:58 AM James Prestwood <prestwoj@gmail.com> wrote:
>> Hi Keith,
>>
>> On 1/3/24 4:56 AM, James Prestwood wrote:
>>> It was seen that this flag seems to cause issues when in AP mode on
>>> brcmfmac devices (e.g. the raspberry Pi 3). When in AP mode an a
>>> scan is issued clients will disconnect. After testing this behavior
>>> was isolated to the use of the COLOCATED_6GHZ flag.
>>>
>>> Besides working around the problem on this specific hardware the
>>> patch itself makes sense as a non-6GHz capable device shouldn't use
>>> this flag anyways.
>>>
>>> As stated in the patch comment, this isn't really a catch all
>>> workaround since the flag is still used for devices supporting 6GHz.
>>> If additional hardware exhibits this behavior we may need additional
>>> changes like a hardware blacklist or an explicit option to disable
>>> the flag.
>>>
>>> Reported-By: Keith G <ys3al35l@gmail.com>
>> Could you double check it still fixes the issue you were seeing on brcmfmac?
>>
>> Thanks,
>>
>> James
>>
>>> ---
>>>    src/scan.c | 15 ++++++++++++++-
>>>    1 file changed, 14 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/src/scan.c b/src/scan.c
>>> index f48ffdef..8c6fdc08 100644
>>> --- a/src/scan.c
>>> +++ b/src/scan.c
>>> @@ -394,7 +394,20 @@ static struct l_genl_msg *scan_build_cmd(struct scan_context *sc,
>>>        if (params->ap_scan)
>>>                flags |= NL80211_SCAN_FLAG_AP;
>>>
>>> -     flags |= NL80211_SCAN_FLAG_COLOCATED_6GHZ;
>>> +     /*
>>> +      * TODO: This flag appears to cause some undesired behavior on brcmfmac
>>> +      *       when the device is in AP mode, or has a secondary AP interface
>>> +      *       running, causing clients to disconnect when a scan is issued.
>>> +      *
>>> +      *       Only using this flag for 6GHz capable devices will limit this
>>> +      *       behavior to only 6GHz devices and in reality makes sense
>>> +      *       because a non-6GHz device shouldn't use this flag anyways. If
>>> +      *       more issues still are seen related to this we may need an
>>> +      *       explicit workaround, either brcmfmac-specific or a disable
>>> +      *       option.
>>> +      */
>>> +     if (wiphy_band_is_disabled(sc->wiphy, BAND_FREQ_6_GHZ) != -ENOTSUP)
>>> +             flags |= NL80211_SCAN_FLAG_COLOCATED_6GHZ;
>>>
>>>        if (flags)
>>>                l_genl_msg_append_attr(msg, NL80211_ATTR_SCAN_FLAGS, 4, &flags);
> James,
>
> I will do this tonight. I was playing a lot with iwd that I had
> patched with your suggestion last night. I was trying to resolve a
> related problem and I did note that it was significantly more stable
> with this patch, but I was still getting disconnected periodically. I
> do not yet know if those disconnects were due to me or iwd and am
> still investigating. I will continue this investigation with this new
> patch applied. SHould this patch be against HEAD or can I safely patch
> 2.12?

Either works, there haven't been changes to that area in a while.

Thanks,

James

>
> Keith