linux-kernel - Re: [PATCH v2 04/18] clocksource: Add ARM System timer driver

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Date:	Mon, 2 Mar 2015 17:53:09 +0100
From:	Maxime Coquelin <mcoquelin.stm32@...il.com>
To:	Paul Bolle <pebolle@...cali.nl>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Cc:	Andreas Färber <afaerber@...e.de>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Rob Herring <robh+dt@...nel.org>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Jonathan Corbet <corbet@....net>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Walleij <linus.walleij@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>, Arnd Bergmann <arnd@...db.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
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	Rusty Russell <rusty@...tcorp.com.au>,
	Kees Cook <keescook@...omium.org>,
	Michal Marek <mmarek@...e.cz>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
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Subject: Re: [PATCH v2 04/18] clocksource: Add ARM System timer driver

Hi Paul, Uwe,

2015-02-20 22:48 GMT+01:00 Paul Bolle <pebolle@...cali.nl>:
> On Fri, 2015-02-20 at 20:54 +0100, Uwe Kleine-König wrote:
>> On Fri, Feb 20, 2015 at 07:01:03PM +0100, Maxime Coquelin wrote:
>> > This patch adds clocksource support for ARMv7-M's System timer,
>> > also known as SysTick.
>> >
>> > Signed-off-by: Maxime Coquelin <mcoquelin.stm32@...il.com>
>> > ---
>> >  drivers/clocksource/Kconfig          |  7 ++++
>> >  drivers/clocksource/Makefile         |  1 +
>> >  drivers/clocksource/armv7m_systick.c | 78 ++++++++++++++++++++++++++++++++++++
>> >  3 files changed, 86 insertions(+)
>> >  create mode 100644 drivers/clocksource/armv7m_systick.c
>> >
>> > diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
>> > index fc01ec2..fb6011e 100644
>> > --- a/drivers/clocksource/Kconfig
>> > +++ b/drivers/clocksource/Kconfig
>> > @@ -124,6 +124,13 @@ config CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
>> >     help
>> >      Use ARM global timer clock source as sched_clock
>> >
>> > +config ARMV7M_SYSTICK
>> > +   bool
>> I assume this symbol is enabled later in the series.
>
> Yes, I noticed it was selected in 14/18 ("ARM: Add STM32 family
> machine").
>
>> Would it make sense
>> to allow enabing the symbol for compile test coverage?
>>
>> > +   select CLKSRC_OF if OF
>> What happens if ARMV7M_SYSTICK=y but OF=n? Doesn't the driver fail to
>> compile?
>>
>> > +   select CLKSRC_MMIO
>> > +   help
>> > +     This options enables support for the ARMv7M system timer unit
>> the right spelling is ARMv7-M.
>
> This Kconfig entry has no prompt, so no one is going to see this text
> during make *config. Perhaps this should be made a comment. In that case
> the right spelling should still be used.

Yes, you are right.
Do you agree if I define it like this:

config ARMV7M_SYSTICK
    bool "Clocksource driver for ARMv7-M System timer"
    depends on OF && (CPU_V7M || COMPILE_TEST)
    select CLKSRC_OF
    select CLKSRC_MMIO
    help
      This options enables clocksource support for the ARMv7-M system
      timer unit.

Thanks,
Maxime
>
> Thanks,
>
>
> Paul Bolle
>
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