From: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
To: Feng Tang <feng.tang@intel.com>
Cc: John Stultz <john.stultz@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>,
Alessandro Zummo <a.zummo@towertech.it>,
linux-kernel@vger.kernel.org, alek.du@intel.com
Subject: Re: [PATCH 1/3] timekeeping: Add persistent_clock_exist flag
Date: Mon, 17 Dec 2012 11:22:02 -0700 [thread overview]
Message-ID: <20121217182202.GA10368@obsidianresearch.com> (raw)
In-Reply-To: <20121217161433.GB4762@feng-snb>
On Tue, Dec 18, 2012 at 12:14:33AM +0800, Feng Tang wrote:
> > Sure, but my view on this is that it has nothing to do with
> > read_persistent_clock. If the RTC driver can run with IRQs off is a
> > property of the RTC driver and RTC hardware - it has nothing to do
> > with the platform. ARM platforms will vary on a machine by machine
> > basis. The rtc-mv driver used on my ARM system is perfectly
> > re-entrant, lots of rtc on SOC drivers will be the same.
> >
> > If this is the only thing keeping you on read_persistent_clock, for
> > real RTCs, then how about a RTC_DEV_SAFE_READ flag (or whatever) in
> > rtc_device.flags?
> >
> > Reserve read_persistent_clock for things like that very specialized
> > non-RTC ARM counter.
>
> Yes, these non-RTC device is one reason for keeping read_persistent_clock,
> one other reason I can think of is the CONFIG_RTC_LIB is not always on by
> default for all Archs, and some platforms may chose to disable it on purpose.
> When CONFIG_RTC_LIB is not set, we need the read_persistent_clock for
> time init/suspend/resume.
I thought your concern was the case where the RTC was turned on and
read_persistent_clock was also turned on. Having a flag in the RTC and
disabling read_persistent_clock for that situation would help you
avoid the double code path to the same hardware.
What is motivating having a RTC but not using RTC lib? Embedded
doesn't seem to the be the case, nearly all the interesting rtcs are
under class rtc....
Jason
next prev parent reply other threads:[~2012-12-17 18:22 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-13 2:05 [PATCH 1/3] timekeeping: Add persistent_clock_exist flag Feng Tang
2012-12-13 2:05 ` [PATCH 2/3] rtc: Skip the suspend/resume handling if persistent clock exist Feng Tang
2012-12-13 2:05 ` [PATCH 3/3] rtc: Skip setting xtime if persisent " Feng Tang
2012-12-14 1:20 ` [PATCH 1/3] timekeeping: Add persistent_clock_exist flag John Stultz
2012-12-14 1:37 ` Feng Tang
2012-12-14 2:00 ` John Stultz
2012-12-14 2:15 ` Feng Tang
2012-12-14 2:38 ` Jason Gunthorpe
2012-12-14 3:13 ` Feng Tang
2012-12-14 4:10 ` Jason Gunthorpe
2012-12-14 21:22 ` John Stultz
2012-12-14 21:56 ` Jason Gunthorpe
2012-12-14 23:23 ` John Stultz
2012-12-17 16:14 ` Feng Tang
2012-12-17 18:22 ` Jason Gunthorpe [this message]
2012-12-18 2:44 ` Feng Tang
2012-12-14 21:36 ` John Stultz
2012-12-20 7:02 ` Feng Tang
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