linux-kernel - Re: [RFC part3 PATCH 2/2] ARM64 / clocksource: Use arch_timer_acpi

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Message-ID: <20131204150709.GF29200@e106331-lin.cambridge.arm.com>
Date:	Wed, 4 Dec 2013 15:07:09 +0000
From:	Mark Rutland <mark.rutland@....com>
To:	Hanjun Guo <hanjun.guo@...aro.org>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Olof Johansson <olof@...om.net>,
	Linus Walleij <linus.walleij@...aro.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	Jon Masters <jonathan@...masters.org>,
	"patches@...aro.org" <patches@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>
Subject: Re: [RFC part3 PATCH 2/2] ARM64 / clocksource: Use
 arch_timer_acpi_init()

On Wed, Dec 04, 2013 at 02:27:22PM +0000, Hanjun Guo wrote:
> On 2013年12月04日 01:08, Mark Rutland wrote:
> > On Tue, Dec 03, 2013 at 04:41:31PM +0000, Hanjun Guo wrote:
> >> Use arch_timer_acpi_init() on ARM64 to initialise arch timer
> >> in ACPI way when DT is not available.
> >>
> >> Signed-off-by: Hanjun Guo <hanjun.guo@...aro.org>
> >> ---
> >>   arch/arm64/kernel/time.c |    4 ++++
> >>   1 file changed, 4 insertions(+)
> >>
> >> diff --git a/arch/arm64/kernel/time.c b/arch/arm64/kernel/time.c
> >> index 29c39d5..fb009da 100644
> >> --- a/arch/arm64/kernel/time.c
> >> +++ b/arch/arm64/kernel/time.c
> >> @@ -67,6 +67,10 @@ void __init time_init(void)
> >>   
> >>   	clocksource_of_init();
> >>   
> >> +	/* if can't be initialised from DT, try ACPI way */
> >> +	if (!arch_timer_get_rate())
> >> +		arch_timer_acpi_init();
> >> +
> > As mentioned on the previous patch, I think for the timebeing we should
> > rely on CNTFREQ.
> >
> > Additionally, if you need to do this we should have an analagous
> > mechanism to clocksource_of_init() that performs this initialisation for
> > ACPI, and here we can call a clocksource_*_init function that does the
> > right thing.
> >
> > There's no need for this file to know anything about ACPI.
> 
> Oh, Amit already have some patches to introduce clocksource_acpi_init()
> like clocksource_of_init() did, please refer to the link below.
> 
> http://marc.info/?l=linaro-acpi&m=138131929721943&w=2
> 
> is this the idea you mentioned in your comments?

Something along those lines is far better than hardcoding
arch_timer_acpi_init here.

Thanks,
Mark.
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