linux-kernel - Re: [RESEND] Fast TSC calibration fails with v3.14-rc1 and later

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Message-ID: <1394596807.26565.135.camel@linux-s257.site>
Date:	Wed, 12 Mar 2014 12:00:07 +0800
From:	joeyli <jlee@...e.com>
To:	Julian Wollrath <jwollrath@....de>
Cc:	Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
	LKML <linux-kernel@...r.kernel.org>, Lee@...utronix.de,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [RESEND] Fast TSC calibration fails with v3.14-rc1 and later

Hi Julian, 

於 二，2014-03-11 於 18:15 +0100，Julian Wollrath 提到：
> Am Tue, 11 Mar 2014 14:56:41 +0100 (CET)
> schrieb Thomas Gleixner <tglx@...utronix.de>:
> > > Ok, via bisecting I found commit
> > > 73f7d1ca32638028e3271f54616773727e2f9f26 (see below) to be the one
> > > that introduced this regression.
> > 
> > Interesting. I have no idea what's going on. But maybe can the ACPI
> > folks shed some light on it.
> 

My patch moved acpi_early_init() to before timekeeping_init() is for
prepare the later using ACPI TAD to set system clock. I think that
because acpi_early_init() setup SCI interrupt and enable acpi subsystem,
it causes fast TSC calibration fail.

> I have absolutely no idea, if it is the right thing to do and why it
> works, but the patch below fixes the problem. Thank you for your help.
> 
> 
> Cheers,
> Julian Wollrath
> 
> From 7664f495039d93adfce073e58840a46549904f04 Mon Sep 17 00:00:00 2001
> From: Julian Wollrath <jwollrath@....de>
> Date: Tue, 11 Mar 2014 18:05:43 +0100
> Subject: [PATCH] Fix fast TSC calibration
> 
> Since commit 73f7d1ca32638028e3271f54616773727e2f9f26 the fast TSC calibration
> failed on a Thinkpad X121e with an AMD E450 APU. Moving acpi_early_init() after
> late_time_init() fixes this.
> 
> Signed-off-by: Julian Wollrath <jwollrath@....de>
> ---
>  init/main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/init/main.c b/init/main.c
> index eb03090cdced..bf9d99148bd6 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -561,7 +561,6 @@ asmlinkage void __init start_kernel(void)
>  	init_timers();
>  	hrtimers_init();
>  	softirq_init();
> -	acpi_early_init();
>  	timekeeping_init();
>  	time_init();
>  	sched_clock_postinit();
> @@ -609,6 +608,7 @@ asmlinkage void __init start_kernel(void)
>  	numa_policy_init();
>  	if (late_time_init)
>  		late_time_init();
> +	acpi_early_init();
>  	sched_clock_init();
>  	calibrate_delay();
>  	pidmap_init();

The late_time_init() dependent on timekeeping_init(), if we don't want
move acpi_early_init() before timekeeping_init() then just direct put it
before efi_enter_virtual_mode() because we tested this changed.

This patch restricts the position to run acpi_early_init() before
timekeeping_init() when only "CMOS RTC Not Present" bit set in FADT.

Could you please help to test it on your machine?


Thanks a lot!
Joey Lee


>>From 8ef4fff76dd2f50bef1e8eb9c96f3b0228a38401 Mon Sep 17 00:00:00 2001
From: Lee, Chun-Yi <jlee@...e.com>
Date: Wed, 12 Mar 2014 11:36:32 +0800
Subject: [PATCH] ACPI / init: Run acpi_early_init() before timekeeping_init() when CMOS RTC Not Present bit set

This is a variant patch from Rafael J. Wysocki's
ACPI / init: Run acpi_early_init() before efi_enter_virtual_mode()

According to Matt Fleming, if acpi_early_init() was executed before
efi_enter_virtual_mode(), the EFI initialization could benefit from
it, so Rafael's patch makes that happen.

And, later we want accessing ACPI TAD device to set system clock, so
move acpi_early_init() before timekeeping_init() when "CMOS RTC Not
Present" bit set. This position is also before efi_enter_virtual_mode().

Signed-off-by: Lee, Chun-Yi <jlee@...e.com>
---
 init/main.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/init/main.c b/init/main.c
index eb03090..e1b69d2 100644
--- a/init/main.c
+++ b/init/main.c
@@ -561,7 +561,9 @@ asmlinkage void __init start_kernel(void)
 	init_timers();
 	hrtimers_init();
 	softirq_init();
-	acpi_early_init();
+	if (acpi_gbl_FADT.header.revision >= 5 &&
+	    acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_CMOS_RTC)
+		acpi_early_init();
 	timekeeping_init();
 	time_init();
 	sched_clock_postinit();
@@ -613,6 +615,9 @@ asmlinkage void __init start_kernel(void)
 	calibrate_delay();
 	pidmap_init();
 	anon_vma_init();
+	if (!(acpi_gbl_FADT.header.revision >= 5 &&
+	      acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_CMOS_RTC))
+		acpi_early_init();
 #ifdef CONFIG_X86
 	if (efi_enabled(EFI_RUNTIME_SERVICES))
 		efi_enter_virtual_mode();
-- 
1.6.4.2



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