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

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Message-ID: <56090C08.8070003@huawei.com>
Date:	Mon, 28 Sep 2015 17:44:40 +0800
From:	"Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To:	Arnd Bergmann <arnd@...db.de>
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 2015/9/28 16:42, Arnd Bergmann wrote:
> 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.

Oh, I described the reason in the reply to Ard Biesheuvel.

https://lkml.org/lkml/2015/9/28/124

> 
>> -----------------------------------
>> 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.

Yes, RTC_CLASS will automatically select RTC_LIB, and will not display EFI_RTC, because
RTC_LIB=y now.

We can select EFI_RTC only when RTC_CLASS is not selected(meanwhile RTC_LIB=n)

> 
>> --------------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.

OK, I will try it tommorrow.

> 
> 	Arnd
> 
> .
> 

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