On Wednesday, March 12, 2014 05:39:15 PM Thomas Gleixner wrote:
> On Wed, 12 Mar 2014, Thomas Gleixner wrote:
> > On Wed, 12 Mar 2014, Thomas Gleixner wrote:
> >
> > > On Wed, 12 Mar 2014, joeyli wrote:
> > > > I think maybe still using ACPI_FADT_NO_CMOS_RTC to check does
> > > > acpi_early_init() need run before timekeeping_init().
> > > > If there have any future machine that applied ACPI TAD but "Fast TSC
> > > > calibration" fail, at least the alternate TSC calibration can work
> > > > around issue.
> > >
> > > Well, it can work around, but it sucks as it's way slower than the
> > > fast one. And we really don't want to pay that price for some half
> > > baken ACPI nonsense.
> > >
> > > Why exactly do you need that ACPI stuff before timekeeping_init()?
> >
> > According to the changelog:
> >
> > And, we want accessing ACPI TAD device to set system clock, so move
> > acpi_early_init() before timekeeping_init(). This final position is
> > also before efi_enter_virtual_mode().
> >
> > Why do we need to access that TAD thing (whatever newfangled that is)
> > at this point?
>
> And we have no support for that nonsense in tree, so why do we need to
> disturb functionality which does not need that at all?
>
> We can revisit the issue when we actually have reached a conclusion
> how to deal with that and when we are merging something which supports
> TAD.
>
> Up to then we really can live without that and put the call just
> before efi_enter_virtual_mode().
I agree, and we need to fix that for 3.14. Patch is appended.
Thanks,
Rafael
---
From: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
Subject: ACPI / init: Invoke early ACPI initialization later
Commit 73f7d1ca3263 (ACPI / init: Run acpi_early_init() before
timekeeping_init()) optimistically moved the early ACPI initialization
before timekeeping_init(), but that didn't work, because it broke fast
TSC calibration for Julian Wollrath on Thinkpad x121e (and most likely
for others too). The reason is that acpi_early_init() enables the SCI
and that interferes with the fast TSC calibration mechanism.
Thus follow the original idea to execute acpi_early_init() before
efi_enter_virtual_mode() to help the EFI people for now and we can
revisit the other problem that commit 73f7d1ca3263 attempted to
address in the future (if really necessary).
Fixes: 73f7d1ca3263 (ACPI / init: Run acpi_early_init() before
timekeeping_init())
Reported-by: Julian Wollrath <jwollr...@web.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
---
init/main.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Index: linux-pm/init/main.c
===================================================================
--- linux-pm.orig/init/main.c
+++ linux-pm/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();
@@ -613,6 +612,7 @@ asmlinkage void __init start_kernel(void
calibrate_delay();
pidmap_init();
anon_vma_init();
+ acpi_early_init();
#ifdef CONFIG_X86
if (efi_enabled(EFI_RUNTIME_SERVICES))
efi_enter_virtual_mode();
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
