wifi: mt76: mt7921 Survey is missing noise floor

[Martin Blumenstingl]

Hello,

On Sun, Oct 13, 2024 at 1:19 PM Martin Blumenstingl
<martin.blumenstingl at googlemail.com> wrote:
>
> Hello,
>
> I'm using an MT7921 PCIe card in AP mode on the 5GHz band.
> It works well when I manually set a channel in hostapd.conf.
>
> Setting channel=0 or channel=acs_survey (both have the same meaning)
> should make hostapd check for a suitable channel and pick that
> automatically.
> Unfortunately this does not work as hostapd reports the following (for
> all frequencies/channels):
>     ACS: Survey for freq 5180 is missing noise floor
>     ACS: Survey for freq 5180 is missing noise floor
>     ACS: Survey for freq 5180 is missing noise floor
>     ACS: Survey for freq 5180 is missing noise floor
>     ACS: Survey for freq 5180 is missing noise floor
>     ACS: Channel 36 has insufficient survey data
>
> I suspect that this is due to mt792x_phy_update_channel() (from
> drivers/net/wireless/mediatek/mt76/mt792x_mac.c) which calls
> mt792x_phy_get_nf(). The latter just returns zero - so it seems
> reading the noise floor from the hardware/firmware is not
> supported yet.
>
> What is needed to implement this? I can test patches or - if
> someone describes which registers to program - I can also write
> a patch and submit it upstream.
It's been a while so I'd like to ping the mt76 maintainers.

Also I want to point out again that I can submit a patch if someone
can provide me with the info on how to get the noise floor from the
hardware/firmware.


Best regards,
Martin