linux-kernel - Re: [PATCH v3 0/5] clocksource: sun5i: Support parent clock rate changes

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Date:	Fri, 20 Mar 2015 21:56:55 +0100
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Hans de Goede <hdegoede@...hat.com>,
	Chen-Yu Tsai <wens@...e.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 0/5] clocksource: sun5i: Support parent clock rate
 changes

Hi,

On Fri, Mar 20, 2015 at 03:04:28PM +0100, Daniel Lezcano wrote:
> On 03/19/2015 11:53 PM, Maxime Ripard wrote:
> >Hi Daniel,
> >
> >On Thu, Mar 05, 2015 at 11:20:51AM +0100, Maxime Ripard wrote:
> >>Hi,
> >>
> >>The Allwinner HS timers have the AHB clock as their parent
> >>clock. Since this clock is shared with other devices, we could very
> >>well have another driver requesting a rate change of that clock,
> >>making our timer change frequency at the same time.
> >>
> >>This is especially true on the A31, where the DMA controller needs to
> >>do such a rate change, making the HS timer unreliable at the time on
> >>the A31.
> >>
> >>This serie makes some cleanups and implements clock notifiers to be
> >>able to reflect such rate changes and make sure that the timer is
> >>always working.
> >>
> >>Maxime
> >>
> >>Changes from v2:
> >>   - Rebased on top of v4.0-rc1
> >>   - Removed the local_irq_save/restore around clockevents_update_freq
> >>
> >>Changes from v1:
> >>   - Changed the interrupt name to its previous value
> >>
> >>Maxime Ripard (5):
> >>   clocksource: sun5i: Switch to request_irq
> >>   clocksource: sun5i: Use of_io_request_and_map
> >>   clocksource: sun5i: Remove sched_clock
> >>   clocksource: sun5i: Refactor the current code
> >>   clocksource: sun5i: Add clock notifiers
> >
> >Have these patches been merged?
> >
> >If not, it woulde be great if the third one ("clocksource: sun5i:
> >Remove sched_clock") was merged for 4.0.
> >
> >The sched_clock we use on some system is this timer's, and since we
> >started using cpufreq, the cpu clock (that is one of the timer's clock
> >indirect parent) now changes, along with the actual sched_clock rate.
> >
> >We can safely remove the sched_clock on those systems, since we have
> >other reliable sched_clock in the system.
> 
> Ok, I applied the patch for v4.0-rc5 but I had to fix a conflict and change
> the changelog.

It looks fine.

Note that the rest of the serie should also be merged, this is just a
temporary measure for 4.0.

> Mind to test it works ?
> 
> git.linaro.org/people/daniel.lezcano/linux.git clockevents/v4.0-rc4

Unfortunately, I won't have access to my boards for ~10 days due to
travel to ELC. Chen-Yu, Hans, could you test this and see if it works?

Thanks,
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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