linux-kernel - Re: [PATCH 2/2] arm64: to allow EFI

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Message-ID: <2245172.1ESUGv0DKo@wuerfel>
Date:	Mon, 28 Sep 2015 10:42:42 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	"Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Kefeng Wang <wangkefeng.wang@...wei.com>,
	Xinwei Hu <huxinwei@...wei.com>, Zefan Li <lizefan@...wei.com>,
	Tianhong Ding <dingtianhong@...wei.com>,
	Hanjun Guo <guohanjun@...wei.com>
Subject: Re: [PATCH 2/2] arm64: to allow EFI_RTC can be selected on ARM64

On Monday 28 September 2015 16:29:57 Leizhen wrote:
> 
> On 2015/9/28 15:35, Arnd Bergmann wrote:
> > On Monday 28 September 2015 13:34:38 Zhen Lei wrote:
> >> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> >> index 07d1811..25cec57 100644
> >> --- a/arch/arm64/Kconfig
> >> +++ b/arch/arm64/Kconfig
> >> @@ -85,7 +85,7 @@ config ARM64
> >>         select PERF_USE_VMALLOC
> >>         select POWER_RESET
> >>         select POWER_SUPPLY
> >> -       select RTC_LIB
> >> +       select RTC_LIB if !EFI
> >>         select SPARSE_IRQ
> >>         select SYSCTL_EXCEPTION_TRACE
> >>         select HAVE_CONTEXT_TRACKING
> > 
> > Sorry, we can't do that: enabling EFI has to be done in a way that it only
> > adds features but not disables them.
> 
> I run "make ARCH=arm64 menuconfig" and found that RTC_CLASS is selected by default. Actually, RTC_LIB only
> controls whether to display some configs when run "make menuconfig". I list all informations below:
> 
> ---------make ARCH=arm64 menuconfig-----
>   [*] Real Time Clock  --->
> 
> ---------drivers/rtc/Kconfig-------
> menuconfig RTC_CLASS
>         bool "Real Time Clock"
>         default n
>         depends on !S390 && !UML
>         select RTC_LIB

Ok, I see. So your patch here has no effect at all and can be dropped, or
we can remove the 'select RTC_LIB' without the EFI dependency.

> -----------------------------------
> find . -name "*Kconfig*" | xargs grep RTC_LIB
> ./drivers/rtc/Kconfig:config RTC_LIB
> ./drivers/rtc/Kconfig:	select RTC_LIB
> ./drivers/char/Kconfig:if RTC_LIB=n
> ./drivers/char/Kconfig:endif # RTC_LIB
> ./arch/x86/Kconfig:	select RTC_LIB
> ./arch/arm/Kconfig:	select RTC_LIB
> ./arch/arm64/Kconfig:	select RTC_LIB if !EFI
> ./arch/sh/Kconfig:	select RTC_LIB
> ./arch/mips/Kconfig:	select RTC_LIB if !MACH_LOONGSON64
> 
> --------------drivers/char/Kconfig--------------
> if RTC_LIB=n
> 
> config RTC
>         tristate "Enhanced Real Time Clock Support (legacy PC RTC driver)"
> 
> .......
> 
> endif # RTC_LIB
> 
> 
> > 
> > Your patch breaks RTC on all non-EFI platforms as soon as CONFIG_EFI
> > is selected by the user.
> 
> No, on non-EFI platforms, they can still use RTC as before. As I mentioned above,
> RTC_LIB only controls whether to display some configs when run "make menuconfig".
> On ARM64, (in this patch) I only allowed EFI_RTC can be showed when RTC_LIB was
> not selected.
>

but that is the wrong driver that uses the legacy API, we cannot have that
on ARM because it conflicts with the normal RTC_CLASS drivers.

> --------------drivers/char/Kconfig--------------
> if RTC_LIB=n
> 
> config RTC
> tristate "Enhanced Real Time Clock Support (legacy PC RTC driver)"
> 
> .......
> 
> config EFI_RTC
>         bool "EFI Real Time Clock Services"
>         depends on IA64 || ARM64
> 
> .......
> 
> endif # RTC_LIB

The driver you want is RTC_DRV_EFI, not EFI_RTC.

	Arnd
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