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

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Message-ID: <4862789.31r3eYUQgx@natalenko.name>
Date:   Thu, 21 Sep 2023 18:03:23 +0200
From:   Oleksandr Natalenko <oleksandr@...alenko.name>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-wireless@...r.kernel.org, Felix Fietkau <nbd@....name>,
        Sasha Levin <sashal@...nel.org>, stable@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] wifi: mt76: mt7915: remove VHT160 capability on MT7915

Hello.

On čtvrtek 21. září 2023 9:19:58 CEST Greg Kroah-Hartman wrote:
> On Thu, Sep 21, 2023 at 07:02:41AM +0200, Oleksandr Natalenko wrote:
> > 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?
> 
> Is your device also broken in 6.6-rc2?

Yes, the same behaviour is observed with v6.6-rc2:

```
hostapd[1316]: Configured VHT capability [VHT_CAP_SUPP_CHAN_WIDTH_MASK] exceeds max value supported by the driver (1 > 0)
```

while having `[VT160]` in `vht_capab=`.

Thanks.

> thanks,
> 
> greg k-h
> 


-- 
Oleksandr Natalenko (post-factum)
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