Re: [PATCH] ACPI / init: Switch over platform to the ACPI mode later

[Hanjun Guo]

On 06/10/2015 07:48 AM, Rafael J. Wysocki wrote:
> On Wednesday, June 03, 2015 11:13:57 AM Toshi Kani wrote:
> > On Sat, 2015-05-30 at 14:21 +0200, Rafael J. Wysocki wrote:
> > > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > >
> > > Commit 73f7d1ca3263 "ACPI / init: Run acpi_early_init() before
> > > timekeeping_init()" moved the ACPI subsystem initialization,
> > > including the ACPI mode enabling, to an earlier point in the
> > > initialization sequence, to allow the timekeeping subsystem
> > > use ACPI early.  Unfortunately, that resulted in boot regressions
> > > on some systems and the early ACPI initialization was moved toward
> > > its original position in the kernel initialization code by commit
> > > c4e1acbb35e4 "ACPI / init: Invoke early ACPI initialization later".
> > >
> > > However, that turns out to be insufficient, as boot is still broken
> > > on the Tyan S8812 mainboard.
> > >
> > > To fix that issue, split the ACPI early initialization code into
> > > two pieces so the majority of it still located in acpi_early_init()
> > > and the part switching over the platform into the ACPI mode goes into
> > > a new function, acpi_subsystem_init(), executed at the original early
> > > ACPI initialization spot.
> > >
> > > That fixes the Tyan S8812 boot problem, but still allows ACPI
> > > tables to be loaded earlier which is useful to the EFI code in
> > > efi_enter_virtual_mode().
> > >
> > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=97141
> > > Reported-and-tested-by: Marius Tolzmann <tolzmann@xxxxxxxxxxxxx>
> > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> >
> > Can you add comments to acpi_early_init() and acpi_subsystem_init() to
> > clarify what ACPI features are enabled at each phase, and what
> > dependency they have in the boot sequence?  (The same goes to
> > early_acpi_boot_init() and acpi_boot_init().)
>
> OK, update follows.
>
> ---
> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> Subject: ACPI / init: Switch over platform to the ACPI mode later
>
> Commit 73f7d1ca3263 "ACPI / init: Run acpi_early_init() before
> timekeeping_init()" moved the ACPI subsystem initialization,
> including the ACPI mode enabling, to an earlier point in the
> initialization sequence, to allow the timekeeping subsystem
> use ACPI early.  Unfortunately, that resulted in boot regressions
> on some systems and the early ACPI initialization was moved toward
> its original position in the kernel initialization code by commit
> c4e1acbb35e4 "ACPI / init: Invoke early ACPI initialization later".
>
> However, that turns out to be insufficient, as boot is still broken
> on the Tyan S8812 mainboard.
>
> To fix that issue, split the ACPI early initialization code into
> two pieces so the majority of it still located in acpi_early_init()
> and the part switching over the platform into the ACPI mode goes into
> a new function, acpi_subsystem_init(), executed at the original early
> ACPI initialization spot.
>
> That fixes the Tyan S8812 boot problem, but still allows ACPI
> tables to be loaded earlier which is useful to the EFI code in
> efi_enter_virtual_mode().
>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=97141
> Fixes: 73f7d1ca3263 "ACPI / init: Run acpi_early_init() before timekeeping_init()"
> Reported-and-tested-by: Marius Tolzmann <tolzmann@xxxxxxxxxxxxx>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> Acked-by: Toshi Kani <toshi.kani@xxxxxx>
> ---
>   drivers/acpi/bus.c   |   56 +++++++++++++++++++++++++++++++++++++--------------
>   include/linux/acpi.h |    2 +
>   init/main.c          |    1
>   3 files changed, 44 insertions(+), 15 deletions(-)
>
> Index: linux-pm/drivers/acpi/bus.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/bus.c
> +++ linux-pm/drivers/acpi/bus.c
> @@ -470,6 +470,16 @@ static int __init acpi_bus_init_irq(void
>   	return 0;
>   }
>
> +/**
> + * acpi_early_init - Initialize ACPICA and populate the ACPI namespace.
> + *
> + * The ACPI tables are accessible after this, but the handling of events has not

Maybe we need to explicitly say that it's DSDT/SSDT, because static
tables such as FADT and MADT are accessible in the very early stage
of boot (in setup_arch()).

Other than that,

Reviewed-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx>

Thanks
Hanjun
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