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

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Date:	Fri, 01 Jul 2016 23:01:57 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:	Hanjun Guo <hanjun.guo@...aro.org>, Fu Wei <fu.wei@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.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 Friday, July 01, 2016 04:00:34 PM Daniel Lezcano wrote:
> On 06/30/2016 03:27 PM, Rafael J. Wysocki wrote:
> 
> [ ... ]
> 
> >> 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/ ?
> 
> Hi Rafael,
> 
> what is the problem of having it in drivers/acpi ?

There's no reason for it to be there.

> There are cpufreq-dt, speedstep*, tegra124-* in drivers/cpufreq.

Yes, they are, but for a reason.  Having them in there makes it easier to
rework and clean up the core.

> clocksource-probe which is DT based with different drivers using it in 
> drivers/clocksource with a pletore of different archs.

So maybe the GTDT code should be there too?

> Cstate code which is only used by x86 is in drivers/acpi, it is only 
> used by x86/ia64 and it isn't a problem.

It is a problem.  drivers/acpi/ is not the right place for arch-specific code.

> There is a small chunk in arch/x86/kernel/acpi and it doesn't facilitate the
> comprehension of the code.
> 
> IMHO, having all ACPI code in the same directory will encourage the 
> consolidation.

The consolidation of what exactly?

In particular, how does the GTDT code in drivers/acpi/ help to consolidate
anything?

Thanks,
Rafael