linux-kernel - Re: [PATCH v3 2/2] PM: ACPI: reboot: Reinstate S5 for reboot

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Date:   Fri, 16 Sep 2022 08:03:16 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Dmitry Osipenko <dmitry.osipenko@...labora.com>
Cc:     rafael.j.wysocki@...el.com, lenb@...nel.org,
        Josef Bacik <josef@...icpanda.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] PM: ACPI: reboot: Reinstate S5 for reboot

On Tue, Sep 13, 2022 at 11:17 PM Dmitry Osipenko
<dmitry.osipenko@...labora.com> wrote:
>
> On 9/13/22 09:20, Kai-Heng Feng wrote:
> > Commit d60cd06331a3 ("PM: ACPI: reboot: Use S5 for reboot") caused Dell
> > PowerEdge r440 hangs at reboot.
> >
> > The issue is fixed by commit 2ca1c94ce0b6 ("tg3: Disable tg3 device on
> > system reboot to avoid triggering AER"), so use the new sysoff API to
> > reinstate S5 for reboot on ACPI-based systems.
> >
> > Cc: Josef Bacik <josef@...icpanda.com>
> > Suggested-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> > ---
> > v3:
> >  - Use new API to invoke ACPI S5.
> >
> > v2:
> >  - Use do_kernel_power_off_prepare() instead.
> >
> >  drivers/acpi/sleep.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c
> > index ad4b2987b3d6e..dce5460902eed 100644
> > --- a/drivers/acpi/sleep.c
> > +++ b/drivers/acpi/sleep.c
> > @@ -1088,6 +1088,10 @@ int __init acpi_sleep_init(void)
> >               register_sys_off_handler(SYS_OFF_MODE_POWER_OFF,
> >                                        SYS_OFF_PRIO_FIRMWARE,
> >                                        acpi_power_off, NULL);
> > +
> > +             register_sys_off_handler(SYS_OFF_MODE_RESTART_PREPARE,
> > +                                      SYS_OFF_PRIO_FIRMWARE,
> > +                                      acpi_power_off_prepare, NULL);
>
> Maybe you could add a small comment to the code explaining why
> acpi_power_off_prepare is used for restarting?

Will do.

>
> Is it safe to use S5 on restart for all devices in general?

S5 should be used, but it may expose some driver bugs like the one
mentioned in the commit message.

Kai-Heng

>
> --
> Best regards,
> Dmitry
>