From mboxrd@z Thu Jan  1 00:00:00 1970
From: tony@atomide.com (Tony Lindgren)
Date: Fri, 2 Dec 2016 10:31:40 -0800
Subject: [PATCH 2/2] ARM: omap: timers: reduce rating of gp_timer
 clocksource
In-Reply-To: <14878d85-1b08-5df1-4e67-6f982ba72019@ti.com>
References: <1479968355-18860-1-git-send-email-j-keerthy@ti.com>
 <1479968355-18860-2-git-send-email-j-keerthy@ti.com>
 <d3a71d3d-3015-bb1f-80a4-4bb9adecaa4c@ti.com>
 <20161202164714.GB4705@atomide.com>
 <14878d85-1b08-5df1-4e67-6f982ba72019@ti.com>
Message-ID: <20161202183139.GF4705@atomide.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

* 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