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

[Linux regression tracking #adding (Thorsten Leemhuis)]

[TLDR: I'm adding this report to the list of tracked Linux kernel
regressions; the text you find below is based on a few templates
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On 21.09.23 07:02, Oleksandr Natalenko wrote:
> 
> 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@xxxxxxxx>
>> ---
>>  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?

Thanks for the report. To be sure the issue doesn't fall through the
cracks unnoticed, I'm adding it to regzbot, the Linux kernel regression
tracking bot:

#regzbot ^introduced 3ec5ac12ac8a4e..fe0ea395f0a351
#regzbot title wifi: mt76: mt7915: removal of VHT160 capability broke hostap
#regzbot ignore-activity

This isn't a regression? This issue or a fix for it are already
discussed somewhere else? It was fixed already? You want to clarify when
the regression started to happen? Or point out I got the title or
something else totally wrong? Then just reply and tell me -- ideally
while also telling regzbot about it, as explained by the page listed in
the footer of this mail.

Developers: When fixing the issue, remember to add 'Link:' tags pointing
to the report (the parent of this mail). See page linked in footer for
details.

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
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