linux-kernel - Re: [PATCHv1] ACPI: processor idle: Allow playing dead in C3 state

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Date:   Fri, 24 Sep 2021 18:31:44 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Richard Gong <richard.gong@....com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        lijo.lazar@....com, Mario Limonciello <mario.limonciello@....com>
Subject: Re: [PATCHv1] ACPI: processor idle: Allow playing dead in C3 state

On Wed, Sep 22, 2021 at 3:31 PM Richard Gong <richard.gong@....com> wrote:
>
> When some cores are disabled on AMD platforms, the system will no longer
> be able to enter suspend-to-idle s0ix.
>
> Update to allow playing dead in C3 state so that the CPUs can enter the
> deepest state on AMD platforms.
>
> BugLink: https://gitlab.freedesktop.org/drm/amd/-/issues/1708
> Suggested-by: Mario Limonciello <mario.limonciello@....com>
> Signed-off-by: Richard Gong <richard.gong@....com>
> ---
>  drivers/acpi/processor_idle.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index f37fba9e5ba0..61d5a72d218e 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -789,7 +789,8 @@ static int acpi_processor_setup_cstates(struct acpi_processor *pr)
>                 state->enter = acpi_idle_enter;
>
>                 state->flags = 0;
> -               if (cx->type == ACPI_STATE_C1 || cx->type == ACPI_STATE_C2) {
> +               if (cx->type == ACPI_STATE_C1 || cx->type == ACPI_STATE_C2
> +                       || cx->type == ACPI_STATE_C3) {
>                         state->enter_dead = acpi_idle_play_dead;
>                         drv->safe_state_index = count;
>                 }
> --

Tentatively applied as 5.16 material, but have you done any research
on why this restriction has been there in the first place?