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

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Message-ID: <2586130.FMgQktF91L@vostro.rjw.lan>
Date:	Thu, 11 Jun 2015 01:17:38 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Hanjun Guo <hanjun.guo@...aro.org>
Cc:	Toshi Kani <toshi.kani@...com>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Len Brown <len.brown@...el.com>,
	Marius Tolzmann <tolzmann@...gen.mpg.de>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Chun-Yi <jlee@...e.com>, Aaron Lu <aaron.lu@...el.com>,
	Lv Zheng <lv.zheng@...el.com>
Subject: Re: [PATCH] ACPI / init: Switch over platform to the ACPI mode later

On Wednesday, June 10, 2015 10:06:40 AM Hanjun Guo wrote:
> 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@...el.com>
> >>>
> >>> 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@...gen.mpg.de>
> >>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >>
> >> 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@...el.com>
> > 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@...gen.mpg.de>
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > Acked-by: Toshi Kani <toshi.kani@...com>
> > ---
> >   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()).

Well, it never says that none of the tables are accessible earlier.

> Other than that,
> 
> Reviewed-by: Hanjun Guo <hanjun.guo@...aro.org>

Thanks!


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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