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From: tony@atomide.com (Tony Lindgren)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 2/2] ARM: omap: timers: reduce rating of gp_timer clocksource
Date: Fri, 2 Dec 2016 10:31:40 -0800	[thread overview]
Message-ID: <20161202183139.GF4705@atomide.com> (raw)
In-Reply-To: <14878d85-1b08-5df1-4e67-6f982ba72019@ti.com>

* Grygorii Strashko <grygorii.strashko@ti.com> [161202 10:02]:
> 
> 
> On 12/02/2016 10:47 AM, Tony Lindgren wrote:
> > * Grygorii Strashko <grygorii.strashko@ti.com> [161129 08:43]:
> > > 
> > > 
> > > On 11/24/2016 12:19 AM, Keerthy wrote:
> > > > From: Grygorii Strashko <grygorii.strashko@ti.com>
> > > > 
> > > > Now ARM Global timer (rating 300) will not be selected as clocksource,
> > > > because it's initialized after OMAP GP Timer (rating 300) and
> > > > Timekeeping core will not allow to replace clocksource with new one if
> > > > both of them have the same rating.
> > > > 
> > > > Reduce rating of OMAP GP Timer (300->290) when it's used as
> > > > clocksource device - this will allow to select ARM Global timer (300)
> > > > as clocksource when enabled.
> > > > 
> > > > Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
> > > > Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
> > > > Signed-off-by: Keerthy <j-keerthy@ti.com>
> > > 
> > > Unfortunately, this patch has dependency [1] and can't be used alone as
> > > it will cause ARM Global timer to be selected as clocksource
> > > always on am437x and this will kill cpuidle, because ARM Global timer
> > > is not in always_on domain.
> > > 
> > > The intention of enabling ARM Global timer is only for non-pm aware use
> > > cases for RT-kernel latency improvement - where deep cpuidle states are not
> > > enabled.
> > 
> > Yeah we need to fix up things to be able to change the clocksource
> > in addition to clockevent. However, currently only cpuidle_coupled
> > knows when the whole system is idle, so quite a bit of work is
> > needed to do that in a sane way.
> 
> Also sched_clock and timer_delay ;)

Yeah sched_clock would need something to save and restore it..
Not nice :)

> > What about the first patch in this series?
> > 
> 
> Fist one is ok. It was originally posted long time ago.

OK so can you please resend that one more time with proper
Fixes tag on it?

Regards,

Tony

  reply	other threads:[~2016-12-02 18:31 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-11-24  6:19 [PATCH 1/2] ARM: omap2: am437x: rollback to use omap3_gptimer_timer_init() Keerthy
2016-11-24  6:19 ` [PATCH 2/2] ARM: omap: timers: reduce rating of gp_timer clocksource Keerthy
2016-11-29 16:43   ` Grygorii Strashko
2016-12-02 16:47     ` Tony Lindgren
2016-12-02 18:02       ` Grygorii Strashko
2016-12-02 18:31         ` Tony Lindgren [this message]
2016-12-05  4:12           ` Keerthy

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