linux-kernel - [regression] Bug 216753 - 6e 6 ghz bands are disabled since 5.16 on intel ax211

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Date:   Thu, 1 Dec 2022 11:14:38 +0100
From:   Thorsten Leemhuis <regressions@...mhuis.info>
To:     Luca Coelho <luciano.coelho@...el.com>
Cc:     "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        Johannes Berg <johannes@...solutions.net>,
        "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>,
        LKML <linux-kernel@...r.kernel.org>, Dave <chiluk@...ntu.com>
Subject: [regression] Bug 216753 - 6e 6 ghz bands are disabled since 5.16 on intel ax211

Hi, this is your Linux kernel regression tracker.

Luca, I noticed a regression report in bugzilla where I'd like your
advice on. To quote https://bugzilla.kernel.org/show_bug.cgi?id=216753

> It looks like the self-managed regulatory information is causing the 6ghz band to be disabled on my AX211 (in the US).  
> iw reg get shows no 6ghz bands (output at the bottom).
> 
> $ sudo iw phy0 channel 
> ...
> Band 4:
> 	* 5955 MHz [1] (disabled)
> 	* 5975 MHz [5] (disabled)
> 	* 5995 MHz [9] (disabled)
>         ....(continues with all disabled 
>         * 7115 MHz [233] (disabled)
> ...
> 
> I was able to narrow this down to having been introduced during the 5.16 development window, as 5.15.79 linux-stable kernel works and the 5.16.12 does 
> not (earlier builds of 5.16 kernel fail to boot on my machine for some reason). 
> 
> I found https://community.frame.work/t/kernel-5-16-6ghz-disabled-ax210/15675/5
> and they imply that this regression was introduced by 
> 698b166ed3464e1604a0e6a3e23cc1b529a5adc1
> I haven't independently verified this commit as the definitive issue.

You authored 698b166ed346 ("iwlwifi: mvm: read 6E enablement flags from
DSM and pass to FW"). As it is a regressions is ideally should be dealt
with. But this area in tricky due to the legal implications. Hence I
wonder: is there anything we can do about this, or is this simply a case
where we have to bite the bullet and live with this regression?

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

P.S.: As the Linux kernel's regression tracker I deal with a lot of
reports and sometimes miss something important when writing mails like
this. If that's the case here, don't hesitate to tell me in a public
reply, it's in everyone's interest to set the public record straight.