linux-kernel - Re: [PATCH v2 3/3] time: clocksource: Add a comment to CLOCK_SOURCE_SUSPEND

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Date:	Thu, 22 Jan 2015 22:07:57 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Xunlei Pang <pang.xunlei@...aro.org>
cc:	linux-kernel@...r.kernel.org, rtc-linux@...glegroups.com,
	Alessandro Zummo <a.zummo@...ertech.it>,
	John Stultz <john.stultz@...aro.org>,
	Arnd Bergmann <arnd.bergmann@...aro.org>
Subject: Re: [PATCH v2 3/3] time: clocksource: Add a comment to
 CLOCK_SOURCE_SUSPEND_NONSTOP

On Thu, 22 Jan 2015, Xunlei Pang wrote:
> When doing timekeeping_resume(), if the nonstop clocksource
> wraps back, "cycle_delta" will miss the wrap time.
> 
> It's hard to determine the right CLOCKSOURCE_MASK(xxx) or
> something to add code for inspecting such behavior, and we
> don't have many existent nonstop clocksources, so just add
> a comment to indicate that if have this flag set, people
> are aware that this nonstop clocksource won't wrap back
> during system suspend/resume.

-ENOPARSE

What has the CLOCKSOURCE_MASK() to do with this and why is the fact
relevant, that we only have a few suspend_nonstop clock sources?

> +
> +/*
> + * When setting this flag, you're also supposed to mean that it doesn't
> + * wrap back during system suspend/resume. See timekeeping_resume().

-ENOPARSE

I guess what you want to say here is:

/*
 * clocksource continues to run during suspend and is guaranteed not to
 * wrap around during long suspend periods.
 */

> + */
>  #define CLOCK_SOURCE_SUSPEND_NONSTOP		0x80

Thanks,

	tglx
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