Re: acpi_cmbat with charge-limited battery

Date: Mon, 06 Mar 2023 03:58:49 UTC
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On Mon, 6 Mar 2023 at 09:03, Warner Losh <> wrote:

> On Sun, Mar 5, 2023 at 7:20 PM Kyle Evans <> wrote:
>> Hello!
>> I've dealt with this mainly over the weekend, but my solution was to
>> just disable acpi_cmbat entirely, which is maybe not the best solution
>> but I can't tell if this should be considered a firmware bug or if
>> it's something we could find a way to workaround in the kernel.
>> Basically, I've set the firmware on my laptop to limit the
>> battery charge to 80%. When it hits 80% while plugged in, things get a
>> little funky- I assume it's because the firmware's trying to carefully
>> maintain the limit, but I end up getting (at least) one acpi
>> notification per second, alternating between BST_CHANGE/BIX_CHANGE,
>> which in turn drives up CPU usage as we tap it out to devd and upowerd
>> picks it up. upowerd ends up pegging a core consistently.
>> Should we be rate-limiting these devd notifications? Is this even
>> reasonable behavior for the firmware? I'm not really sure how other OS
>> behave here, but I haven't really seen any complaints from other
>> framework'ers.
> Seems like this is crappy firmware behavior and we should rate
> limit in the driver... It's not useful information to be sharing once
> a second...
> Warner