linux-kernel - Re: [PATCH 4/4] ACPI: PM: Avoid cache flush on entering S4

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Date:   Wed, 8 Dec 2021 17:16:11 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tony Luck <tony.luck@...el.com>,
        "the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: [PATCH 4/4] ACPI: PM: Avoid cache flush on entering S4

On Wed, Dec 8, 2021 at 5:04 PM Kirill A. Shutemov
<kirill.shutemov@...ux.intel.com> wrote:
>
> On Wed, Dec 08, 2021 at 04:10:52PM +0100, Rafael J. Wysocki wrote:
> > On Mon, Dec 6, 2021 at 1:30 PM Kirill A. Shutemov
> > <kirill.shutemov@...ux.intel.com> wrote:
> > >
> > > According to the ACPI spec v6.4, section 16.2 the cache flushing
> > > required on entering to S1, S2, and S3.
> > >
> > > No need to flush caches on hibernation (S4).
> > >
> > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> > > ---
> > >  drivers/acpi/sleep.c | 2 --
> > >  1 file changed, 2 deletions(-)
> > >
> > > diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c
> > > index 14e8df0ac762..8166d863ed6b 100644
> > > --- a/drivers/acpi/sleep.c
> > > +++ b/drivers/acpi/sleep.c
> > > @@ -902,8 +902,6 @@ static int acpi_hibernation_enter(void)
> > >  {
> > >         acpi_status status = AE_OK;
> > >
> > > -       ACPI_FLUSH_CPU_CACHE();
> > > -
> > >         /* This shouldn't return.  If it returns, we have a problem */
> > >         status = acpi_enter_sleep_state(ACPI_STATE_S4);
> > >         /* Reprogram control registers */
> > > --
> >
> > Applied (with some edits in the subject and changelog) as 5.17 material, thanks!
>
> Is it for the series or only 4/4?

Just for the [4/4].

> Do I need to do something for 2/4 and 3/4?

For [2/4] you do as per the comment and let me reply to the [3/4].