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

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Date:   Fri, 2 Dec 2022 17:02:47 +0100
From:   Thorsten Leemhuis <regressions@...mhuis.info>
To:     Dave Chiluk <chiluk@...ntu.com>,
        "Coelho, Luciano" <luciano.coelho@...el.com>
Cc:     "Greenman, Gregory" <gregory.greenman@...el.com>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "johannes@...solutions.net" <johannes@...solutions.net>,
        "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [regression] Bug 216753 - 6e 6 ghz bands are disabled since 5.16
 on intel ax211

On 02.12.22 16:37, Dave Chiluk wrote:
> The other possibility is that this is actually a bios bug, as the DSM
> is being read out of ACPI.  In which case that would be Dell's fault.

Yes and no, but no:

A kernel change exposed this problem, hence it doesn't matter if the
BIOS is faulty: it's makes it a kernel regression and those are not
allowed. For more on this see
https://docs.kernel.org/admin-guide/reporting-issues.html

That at least would be the normal approach. But the thing is: the legal
implications when it comes to things like wifi make this somewhat
trickier. :-/

> On Thu, Dec 1, 2022 at 5:33 AM Coelho, Luciano <luciano.coelho@...el.com> wrote:
>>
>> On Thu, 2022-12-01 at 11:14 +0100, Thorsten Leemhuis wrote:
>>> 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
>>
>> Hi Thorsten wearing-the-regression-hat, 🙂

:-D

>> I'm not the maintainer of iwlwifi anymore, so I'm adding the new
>> maintainer here, Gregory Greenman.

Well, you where the author of the commit, that's why I addressed you.
But if Gregory or someone else steps in that's of course totally fine
for me as well. :-D

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.

>> Gregory, can you take a look?
>>
>>
>>>> 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.
> 
>