linux-kernel - Re: [PATCH] rtc: Disable EFI rtc for x86

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Message-ID: <1412348517.5410.13.camel@deneb.redhat.com>
Date:	Fri, 03 Oct 2014 11:01:57 -0400
From:	Mark Salter <msalter@...hat.com>
To:	Matt Fleming <matt@...sole-pimps.org>
Cc:	Alessandro Zummo <a.zummo@...ertech.it>,
	rtc-linux@...glegroups.com, linux-efi@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Matt Fleming <matt.fleming@...el.com>,
	Dave Young <dyoung@...hat.com>
Subject: Re: [PATCH] rtc: Disable EFI rtc for x86

On Fri, 2014-10-03 at 13:32 +0100, Matt Fleming wrote:
> From: Matt Fleming <matt.fleming@...el.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@...hat.com>
> Cc: Dave Young <dyoung@...hat.com>
> Cc: Alessandro Zummo <a.zummo@...ertech.it>
> Signed-off-by: Matt Fleming <matt.fleming@...el.com>
> ---

Acked-by: Mark Salter <msalter@...hat.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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