Re: [PATCH] brcmfmac: firmware: Treat EFI nvram ccode=XT the same as ccode=XV

[Kalle Valo <kvalo@codeaurora.org>]

Arend van Spriel <aspriel@gmail.com> writes:

> On Tue, Oct 5, 2021 at 10:02 AM Hans de Goede <hdegoede@redhat.com> wrote:
>>
>> Hi Kalle,
>>
>> On 10/5/21 7:36 AM, Kalle Valo wrote:
>> > Hans de Goede <hdegoede@redhat.com> writes:
>> >
>> >> In some cases the EFI-var stored nvram contains "ccode=ALL", "ccode=XV"
>> >> or "ccode=XT", to specify "worldwide" compatible settings, but these
>> >> ccode-s do not work properly. "ccode=ALL" causes channels 12 and 13 to
>> >> not be available, "ccode=XV" / "ccode=XT" may cause all 5GHz channels
>> >> to not be available.
>> >>
>> >> ccode="ALL" and ccode="XV" where already being replaced with ccode="X2"
>> >> with a bit of special handling for nvram settings coming from an EFI
>> >> variable. Extend this handling to also deal with nvram settings from
>> >> EFI variables which contain "ccode=XT", which has similar issues to
>> >> "ccode=XV".
>> >>
>> >> This fixes 5GHz wifi not working on the HP ElitePad 1000 G2.
>> >>
>> >> This was also tested on a Lenovo Thinkpad 8 tablet which also uses
>> >> "ccode=XT" and this causes no adverse effects there.
>> >>
>> >> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> >
>> > To me worldwide compatible settings mean that channels 12 and 13 should
>> > be disabled, so I'm quite hesitant about this patch.
>>
>> The X2 setting puts channel 12 and 13 in passive / listen-only modes
>> and only starts using them if there is an AP on them.
>>
>> AFAIK this is the same with the XT/XV settings. The problem is that the XT
>> setting results in 5G not being available on some boards even though the
>> hw supports it.
>>
>> Also note that we already use the X2 setting for any EFI supplied nvram
>> files where ccode=ALL or ccode=XV, this just extends the handling we
>> already have to also patch ccode=XT.
>
> I am not overly excited about this approach that is already in use.
> AFAIK these worldwide codes are tailored for specific
> devices/customers based on their RF components. Using it as fallback
> for other devices in such a generic way could even result in exceeding
> regulatory limits. However, I do not have a better solution for this.
> I am surprised to learn there are nvram out there with ccode=ALL as
> that is for internal use only, but if these devices has SROM than the
> nvram value is ignored. Hopefully, that is the case although given the
> fact that changing it to X2 helps suggests otherwise :-(

What's the conclusion? Should I take this or drop it?

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