RE: [PATCH][RFC,v4] ACPI / PM: Introduce efi poweroff for HW-full platforms without _S5

From: Chen, Yu C
Date: Fri Mar 11 2016 - 11:33:57 EST



Hi Matt,

> -----Original Message-----
> From: Matt Fleming [mailto:matt@xxxxxxxxxxxxxxxxxxx]
> Sent: Friday, March 11, 2016 11:56 PM
> To: Chen, Yu C
> Cc: linux-acpi@xxxxxxxxxxxxxxx; linux-pm@xxxxxxxxxxxxxxx; Rafael J. Wysocki;
> Len Brown; Thomas Gleixner; Ingo Molnar; H. Peter Anvin; Zhang, Rui; linux-
> efi@xxxxxxxxxxxxxxx; x86@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Ard
> Biesheuvel; Mark Salter
> Subject: Re: [PATCH][RFC,v4] ACPI / PM: Introduce efi poweroff for HW-full
> platforms without _S5
>
> On Fri, 11 Mar, at 05:05:33PM, Chen Yu wrote:
> > The problem is Linux registers pm_power_off = efi_power_off only if we
> > are in hardware reduced mode. Actually, what we also want is to do
> > this when ACPI S5 is simply not supported on non-legacy platforms.
> > That should handle both the HW reduced mode, and the HW-full mode
> > where the DSDT fails to supply an _S5 object.
> >
> > This patch introduces pm_power_off_default which would be used by
> > pm_power_off if nothing else is available. And in this case we
> > leverage efi power off to be this role. However since efi power off
> > may not be stable enough thus in order not to interfere with other
> > poweroff path, we only make a minimum enhancement for x86 in
> > native_machine_power_off.
> >
> > Suggested-by: Len Brown <len.brown@xxxxxxxxx>
> > Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
> > ---
> > v4:
> > - Since in v3 efi_poweroff_required() is not guaranteed to run
> > after all of the other code that may register alternative
> > power off handling, add the pm_power_off_default that would
> > be used by pm_power_off if nothing else is available.
> > v3:
> > - Only assign pm_power_off to efi_power_off when there are no
> > other pm_power_off registered at that time, in case other
> > commponents would like to customize their own implementation.
> > ---
> > v2:
> > - Convert the acpi_no_s5 to a global bool variable in sleep.c and
> > add a declaration to include/linux/acpi.h.
> > ---
> > arch/x86/kernel/reboot.c | 3 +++
> > arch/x86/platform/efi/quirks.c | 5 +++++
> > drivers/acpi/sleep.c | 7 +++++++
> > drivers/firmware/efi/reboot.c | 8 ++++++++
> > include/linux/acpi.h | 1 +
> > include/linux/efi.h | 1 +
> > include/linux/pm.h | 1 +
> > kernel/reboot.c | 1 +
> > 8 files changed, 27 insertions(+)
>
> Couple of things,
>
> 1) I'm still waiting for an answer to my question on whether
> platforms without _S5 that need EFI reset actually exist. You
> said they "might" exist, which makes this all sound very
> speculative. It is not obvious to me that this approach makes
> sense.
There is a future Base-IA platform, we are planning to skip
implementing the SLP_TYP register and the S5 object. (already there
will be no S3 and no S4)

>
> 2) In v4 you're modifying the generic EFI reboot code and should Cc
> other developers who might care, e.g. the arm64 folks. I've Cc'd
> them now.
OK, thanks.

yu