linux-kernel - Re: [GIT PULL] ACPI fixes for v5.18-rc5

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Date:   Thu, 28 Apr 2022 21:49:53 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] ACPI fixes for v5.18-rc5

On Thu, Apr 28, 2022 at 8:50 PM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> On Thu, Apr 28, 2022 at 8:30 AM Rafael J. Wysocki <rafael@...nel.org> wrote:
> >
> >  - Make the ACPI processor driver avoid falling back to C3 type of
> >    C-states when C3 cannot be requested (Ville Syrjälä).
>
> Hmm.
>
> Doesn't this avoid C3 for _everybody_ rather than some conditional
> "when C3 cannot be requested"?

The bug was that if acpi_idle_bm_check() returned 1, it would "fall
back"  to the same state via safe_state_index.

> Of course, it looks like the 'has_lpi' state still potentially allows
> C3 even for busmastering sleeps. Maybe that is what you meant.

That too.

Thanks for pulling!

Rafael