linux-kernel - Re: [PATCH v2 6/7] Watchdog: introduce ARM SBSA watchdog driver

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Message-ID: <20150521155950.GA18300@roeck-us.net>
Date:	Thu, 21 May 2015 08:59:50 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Fu Wei <fu.wei@...aro.org>
Cc:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	Linaro ACPI Mailman List <linaro-acpi@...ts.linaro.org>,
	linux-watchdog@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	Wei Fu <tekkamanninja@...il.com>,
	G Gregory <graeme.gregory@...aro.org>,
	Al Stone <al.stone@...aro.org>,
	Hanjun Guo <hanjun.guo@...aro.org>,
	Timur Tabi <timur@...eaurora.org>,
	Ashwin Chaugule <ashwin.chaugule@...aro.org>,
	Arnd Bergmann <arnd@...db.de>, vgandhi@...eaurora.org,
	wim@...ana.be, Jon Masters <jcm@...hat.com>,
	Leo Duran <leo.duran@....com>, Jon Corbet <corbet@....net>,
	Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v2 6/7] Watchdog: introduce ARM SBSA watchdog driver

On Thu, May 21, 2015 at 11:46:53PM +0800, Fu Wei wrote:
> Hi Guenter,
> 
[ ... ]

> >> >> +
> >> >> +       /*
> >> >> +        * Try to determine the frequency from the arch_timer interface
> >> >> +        */
> >> >> +       clk = arch_timer_get_rate();
> >> >
> >> >
> >> > arch_timer_get_rate() does not seem to be exported. Did you try to build
> >> > the driver as module ?
> >>
> >> yes, I have built it as a ko module, that is why I made a patch to
> >> export this interface in the first patch of this patchset
> >>
> >>  but I will confirm it again :-)
> >>
> > Guess I'll give it a try myself. I don't really understand how this
> > can work unless arch_timer_get_rate() is exported in your tree.
> 
> yes, I have exported it , I think it make sense to export it.
> Because other driver maybe need to get system counter info
> 
> Do you agree ? :-)
> 
I don't think it is for me to agree or not. The arm maintainers
will need to be involved. You can not just export such a function
without maintainer Ack.

Having said that, my personal preference would be for the counter
and rate to be exported through the clock subsystem (ie with
clk_get_rate). But that would still not provide the current counter
value, so maybe that isn't even possible.

Thanks,
Guenter
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