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

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Date:   Wed, 8 Dec 2021 16:10:52 +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 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!