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

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Message-ID: <55795693.2060805@linaro.org>
Date:	Thu, 11 Jun 2015 17:36:19 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
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 06/11/2015 07:17 AM, Rafael J. Wysocki wrote:
> 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.

Ah, that makes sense :)

Thanks
Hanjun
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