linux-kernel - Re: [PATCH 1/3] wifi: mt76: mt7915: remove VHT160 capability on MT7915

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Date:   Thu, 21 Sep 2023 07:02:41 +0200
From:   Oleksandr Natalenko <oleksandr@...alenko.name>
To:     linux-wireless@...r.kernel.org
Cc:     Felix Fietkau <nbd@....name>, Sasha Levin <sashal@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] wifi: mt76: mt7915: remove VHT160 capability on MT7915

Hello Felix.

On středa 26. července 2023 11:17:02 CEST Felix Fietkau wrote:
> The IEEE80211_VHT_CAP_EXT_NSS_BW value already indicates support for half-NSS
> 160 MHz support, so it is wrong to also advertise full 160 MHz support.
> 
> Fixes: c2f73eacee3b ("wifi: mt76: mt7915: add back 160MHz channel width support for MT7915")
> Signed-off-by: Felix Fietkau <nbd@....name>
> ---
>  drivers/net/wireless/mediatek/mt76/mt7915/init.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/mediatek/mt76/mt7915/init.c b/drivers/net/wireless/mediatek/mt76/mt7915/init.c
> index ee976657bfc3..78552f10b377 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt7915/init.c
> +++ b/drivers/net/wireless/mediatek/mt76/mt7915/init.c
> @@ -414,7 +414,6 @@ mt7915_init_wiphy(struct mt7915_phy *phy)
>  			if (!dev->dbdc_support)
>  				vht_cap->cap |=
>  					IEEE80211_VHT_CAP_SHORT_GI_160 |
> -					IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_160MHZ |
>  					FIELD_PREP(IEEE80211_VHT_CAP_EXT_NSS_BW_MASK, 1);
>  		} else {
>  			vht_cap->cap |=
> 

For some reason this got backported into the stable kernel:

```
$ git log --oneline v6.5.2..v6.5.4 -- drivers/net/wireless/mediatek/mt76/mt7915/
c43017fbebcc3 wifi: mt76: mt7915: fix power-limits while chan_switch
edb1afe042c74 wifi: mt76: mt7915: fix tlv length of mt7915_mcu_get_chan_mib_info
9ec0dec0baea3 wifi: mt76: mt7915: remove VHT160 capability on MT7915
0e61f73e6ebc0 wifi: mt76: mt7915: fix capabilities in non-AP mode
6bce28ce28390 wifi: mt76: mt7915: fix command timeout in AP stop period
7af917d4864c6 wifi: mt76: mt7915: rework tx bytes counting when WED is active
feae00c6468ce wifi: mt76: mt7915: rework tx packets counting when WED is active
70bbcc4ad6544 wifi: mt76: mt7915: fix background radar event being blocked
```

and this broke my mt7915-based AP.

However, if I remove `[VT160]` capability from the hostapd config, things go back to normal. It does seem that 160 MHz still works even.

Is this expected?

Please check.

Thanks.

-- 
Oleksandr Natalenko (post-factum)
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