Re: [PATCH] rtc: Disable EFI rtc for x86

Pali Rohár
2014-11-09T17:37:52Z

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On Friday 03 October 2014 17:01:57 Mark Salter wrote:
> On Fri, 2014-10-03 at 13:32 +0100, Matt Fleming wrote:
> > From: Matt Fleming <matt.fleming@intel.com>
> >
> > commit da167ad7638759 ("rtc: ia64: allow other architectures
> > to use EFI RTC") inadvertently introduced a regression for
> > x86. We've been careful not to enable the EFI rtc driver
> > for x86 due to the generally buggy implementations of the
> > time-related EFI runtime services.
> >
> > Previous attempts have been made to us the time EFI
> > services, but all have eventually been reverted due to
> > crashes inside the firmware code.
> >
> > In fact, since the above commit was merged we've seen
> > reports of crashes on 32-bit tablets,
> >
> > https://bugzilla.kernel.org/show_bug.cgi?id=84241#c21
> >
> > Disable it explicitly for x86 so that we don't give users
> > false hope that this driver will work - it won't, and your
> > machine is likely to crash.
> >
> > Cc: Mark Salter <msalter@redhat.com>
> > Cc: Dave Young <dyoung@redhat.com>
> > Cc: Alessandro Zummo <a.zummo@towertech.it>
> > Signed-off-by: Matt Fleming <matt.fleming@intel.com>
> > ---
>
> Acked-by: Mark Salter <msalter@redhat.com>
>
> > Unless anyone objects, I'm happy to take this through the
> > EFI tree.
> >
> > drivers/rtc/Kconfig | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
> > index a168e96142b9..54ef393b0def 100644
> > --- a/drivers/rtc/Kconfig
> > +++ b/drivers/rtc/Kconfig
> > @@ -806,7 +806,7 @@ config RTC_DRV_DA9063
> >
> > config RTC_DRV_EFI
> >
> > tristate "EFI RTC"
> >
> > - depends on EFI
> > + depends on EFI && !X86
> >
> > help
> >
> > If you say yes here you will get support for the EFI
> > Real Time Clock.
>
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Hello,

this patch totally disabled efi rfc driver on x86 machines at
compile time. But on some x86 machines it working without crash
and reading from file /sys/class/rtc/rtc*/since_epoch returns
correct information. So why to disable compiling driver on
machines where driver working?

--
Pali Rohár
pali.rohar@gmail.com

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