linux-kernel - Re: [PATCH v6 00/10] acpi, clocksource: add GTDT driver and GTDT support in arm_arch

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Date:	Thu, 30 Jun 2016 21:48:02 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>
Cc:	Fu Wei <fu.wei@...aro.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Marc Zyngier <marc.zyngier@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	rruigrok@...eaurora.org, harba@...eaurora.org,
	Christopher Covington <cov@...eaurora.org>,
	Timur Tabi <timur@...eaurora.org>,
	G Gregory <graeme.gregory@...aro.org>,
	Al Stone <al.stone@...aro.org>, Jon Masters <jcm@...hat.com>,
	wei@...hat.com, Arnd Bergmann <arnd@...db.de>,
	Wim Van Sebroeck <wim@...ana.be>,
	Suravee Suthikulanit <Suravee.Suthikulpanit@....com>,
	Leo Duran <leo.duran@....com>
Subject: Re: [PATCH v6 00/10] acpi, clocksource: add GTDT driver and GTDT
 support in arm_arch_timer

On 2016/6/30 21:27, Rafael J. Wysocki wrote:
> On Thursday, June 30, 2016 10:10:02 AM Hanjun Guo wrote:
>> Hi Rafael,
>>
>> On 2016/6/30 9:37, Rafael J. Wysocki wrote:
>>> On Thursday, June 30, 2016 09:29:59 AM Fu Wei wrote:
>>>> Hi Rafael,
>>>>
>>>> On 30 June 2016 at 05:32, Rafael J. Wysocki <rafael@...nel.org> wrote:
>>>>> On Wed, Jun 29, 2016 at 8:15 PM,  <fu.wei@...aro.org> wrote:
>>>>>> From: Fu Wei <fu.wei@...aro.org>
>>>>>>
>>>>>> This patchset:
>>>>>>     (1)Preparation for adding GTDT support in arm_arch_timer
>>>>>>         1. Move some enums and marcos to header file
>>>>>>         2. Add a new enum for spi type.
>>>>>>         3. Improve printk relevant code
>>>>>>
>>>>>>     (2)Introduce ACPI GTDT parser: drivers/acpi/gtdt.c
>>>>>>     Parse all kinds of timer in GTDT table of ACPI:arch timer,
>>>>>>     memory-mapped timer and SBSA Generic Watchdog timer.
>>>>>>     This driver can help to simplify all the relevant timer drivers,
>>>>>>     and separate all the ACPI GTDT knowledge from them.
>>>>>>
>>>>>>     (3)Simplify ACPI code for arm_arch_timer
>>>>>>
>>>>>>     (4)Add GTDT support for ARM memory-mapped timer
>>>>>
>>>>> GTDT is ARM-specific AFAICS.
>>>>
>>>> yes, you are right, it is.
>>>>
>>>>>
>>>>> If so, why do we need that code to reside in drivers/acpi/ ?
>>>>
>>>> Although  the GTDT is just for ARM64, but this driver is parsing one
>>>> of ACPI table,
>>>> I think that could be treated as ACPI driver.  Do I miss something? :-)
>>>
>>> Yes, you are.  Nobody except for ARM64 will ever need it.
>>
>> GTDT is part of ACPI spec, drivers/acpi/ is for driver code of
>> ACPI spec, I think it can stay in drivers/acpi/ from this point
>> of view, am I right?
>
> The question is not "Can it?", but "Does it need to?".
>
> It is in the spec, but still there's only one architecture needing it.
>
> There is no way to test it on any other architecture and no reason to build it
> for any other architecture, so why does it need to be located in drivers/acpi/ ?

I'm fine to move it to other places such as arch/arm64/kernel/, but I
would like to ask ARM64 maintainer's suggestion for this.

Will, Catalin, what's your opinion on this?

Thanks
Hanjun