linux-kernel - Re: [PATCH 2/2] ARM: omap: timers: reduce rating of gp

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Message-ID: <20161202183139.GF4705@atomide.com>
Date:   Fri, 2 Dec 2016 10:31:40 -0800
From:   Tony Lindgren <tony@...mide.com>
To:     Grygorii Strashko <grygorii.strashko@...com>
Cc:     Keerthy <j-keerthy@...com>, t-kristo@...com, linux@...linux.org.uk,
        linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Dave Gerlach <d-gerlach@...com>
Subject: Re: [PATCH 2/2] ARM: omap: timers: reduce rating of gp_timer
 clocksource

* Grygorii Strashko <grygorii.strashko@...com> [161202 10:02]:
> 
> 
> On 12/02/2016 10:47 AM, Tony Lindgren wrote:
> > * Grygorii Strashko <grygorii.strashko@...com> [161129 08:43]:
> > > 
> > > 
> > > On 11/24/2016 12:19 AM, Keerthy wrote:
> > > > From: Grygorii Strashko <grygorii.strashko@...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@...com>
> > > > Signed-off-by: Dave Gerlach <d-gerlach@...com>
> > > > Signed-off-by: Keerthy <j-keerthy@...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