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

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Message-ID: <20150323165405.GB15676@lukather>
Date:	Mon, 23 Mar 2015 09:54:05 -0700
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Hans de Goede <hdegoede@...hat.com>
Cc:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Chen-Yu Tsai <wens@...e.org>,
	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

On Sat, Mar 21, 2015 at 11:43:56AM +0100, Hans de Goede wrote:
> Hi,
> 
> On 20-03-15 21:56, Maxime Ripard wrote:
> >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?
> 
> I've just given this a test run on an A20 board, using the dmesg
> timestamps are off reproducer discussed before, and the problem no
> longer reproduces on the clockevents/4.0-rc4 branch, and everything
> else still seems to work fine.

Great, thanks!

Maxime

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

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