mt76: MT7921K monitor mode not working

[sean.wang at mediatek.com]

From: Sean Wang <sean.wang at mediatek.com>

>> On Thursday, 2 December 2021 23:13:31 CET Lorenzo Bianconi wrote:
>> > IIRC you need to disable runtime-pm and deep-sleep to proper enable
>> > monitor
>> > mode:
>> >
>> > echo 0 > /sys/kernel/debug/ieee80211/phy<x>/mt76/runtime-pm
>> > echo 0 > /sys/kernel/debug/ieee80211/phy<x>/mt76/deep-sleep
>> >
>> > Can you please give it whirl?
>>
>> Jan gave me the card. I've set it to a rather busy channel (2.4GHz
>> channel 11), created a monitor interface, attached tcpdump and then
>> waited what happens. I didn't get anything and then I've tried to set
>> runtime-pm and deep- sleep to 0. This didn't change the behavior for
>> me at lot. I saw two packets and then it went silent again.
>>
>> I wanted to try the same on a different card (ath11k) in the same
>> system. But it crashed my complete system - so I had to recreate the
>> test setup. This time, I've set runtime-pm + deep-sleep to 0 before
>> creating mon0. After doing this, it seemed to work.
>
>interesting, adding Sean to the loop here.
>It seems the fw is mainting a different state in this case.

fw cannot receive any frame on monitor mode in deeply doze mode

so it seemed to me we need a patch to explicitly disable pm runtime in driver when monitor interface is enabled until it is being disabled.

>
>@Sean: any pointers?
>
>Regards,
>Lorenzo
>
>>
>> Kind regards,
>>	Sven
>