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SubjectRe: [PATCH v7 12/13] ACPI / init: Invoke early ACPI initialization earlier
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Hi,

At 07/14/2017 01:52 PM, Dou Liyang wrote:
> Linux uses acpi_early_init() to put the ACPI table management into
> the late stage from the early stage where the mapped ACPI tables is
> temporary and should be unmapped.
>
> But, now initializing interrupt delivery mode should map and parse the
> DMAR table earlier in the early stage. This causes an ACPI error when
> Linux reallocates the ACPI root tables. Because Linux doesn't unmapped
> the DMAR table after using in the early stage.
>
> Invoke acpi_early_init() earlier before late_time_init(), Keep the DMAR
> be mapped and parsed in late stage like before.
>
> Reported-by: Xiaolong Ye <xiaolong.ye@intel.com>
> Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
> Cc: linux-acpi@vger.kernel.org
> Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
> Cc: Zheng, Lv <lv.zheng@intel.com>
> Cc: Julian Wollrath <jwollrath@web.de>
> ---
> Test in my own PC(Lenovo M4340).
> Ask help for doing regression testing for the bug said in commit c4e1acbb35e4
> ("ACPI / init: Invoke early ACPI initialization later").
>

Now, I can prove this patch doesn't result in the bug[1] which made the
fast TSC calibration using PIT failed in a Thinkpad x121e (AMD E-450
APU).

The true reason of the bug is enabling ACPI subsystem earlier than
using PIT, not the SCI setup. invoking acpi_enable_subsystem() later
could fix this bug as Julian tested and said[2].

And, I found that Commit b064a8fa77df (" ACPI / init: Switch over
platform to the ACPI mode later") split the ACPI early initialization
code into acpi_early_init() and acpi_subsystem_init(). executing
acpi_enable_subsystem() at the original early ACPI initialization spot.

The sequence of them shows below:

start_kernel
+---------------+
|
+--> .......
|
| late_time_init()
+--> +-------+
|
+--> .......
|
| acpi_early_init()
+--> +-------+
|
+--> .......
|
| acpi_subsystem_init()
+-> +--------+

We make sure the acpi_subsystem_init() is called later than
late_time_init(), the bug will be avoided.

This patch changes the sequence of late_time_init() and
acpi_early_init(), doesn't effect acpi_subsystem_init().

So, this patch is OK.

Btw, Thanks very much for Borislav Petkov, he will have access to
Thinkpad x121e from Mid-August and will test this series.

[1] https://lkml.org/lkml/2014/3/10/123
[2] https://lkml.org/lkml/2014/3/12/311


Thanks
dou.

> init/main.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/init/main.c b/init/main.c
> index df58a41..7a09467 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -654,12 +654,12 @@ asmlinkage __visible void __init start_kernel(void)
> kmemleak_init();
> setup_per_cpu_pageset();
> numa_policy_init();
> + acpi_early_init();
> if (late_time_init)
> late_time_init();
> calibrate_delay();
> pidmap_init();
> anon_vma_init();
> - acpi_early_init();
> #ifdef CONFIG_X86
> if (efi_enabled(EFI_RUNTIME_SERVICES))
> efi_enter_virtual_mode();
>


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