From mboxrd@z Thu Jan 1 00:00:00 1970 From: tony@atomide.com (Tony Lindgren) Date: Fri, 2 Dec 2016 08:47:14 -0800 Subject: [PATCH 2/2] ARM: omap: timers: reduce rating of gp_timer clocksource In-Reply-To: References: <1479968355-18860-1-git-send-email-j-keerthy@ti.com> <1479968355-18860-2-git-send-email-j-keerthy@ti.com> Message-ID: <20161202164714.GB4705@atomide.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org * Grygorii Strashko [161129 08:43]: > > > On 11/24/2016 12:19 AM, Keerthy wrote: > > From: Grygorii Strashko > > > > 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 > > Signed-off-by: Dave Gerlach > > Signed-off-by: Keerthy > > 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. What about the first patch in this series? Regards, Tony > [1] https://patchwork.kernel.org/patch/8940051/ > > > --- > > arch/arm/mach-omap2/timer.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c > > index b2f2448..a0dbb0b 100644 > > --- a/arch/arm/mach-omap2/timer.c > > +++ b/arch/arm/mach-omap2/timer.c > > @@ -376,7 +376,7 @@ static cycle_t clocksource_read_cycles(struct clocksource *cs) > > } > > > > static struct clocksource clocksource_gpt = { > > - .rating = 300, > > + .rating = 290, > > .read = clocksource_read_cycles, > > .mask = CLOCKSOURCE_MASK(32), > > .flags = CLOCK_SOURCE_IS_CONTINUOUS, > > > > -- > regards, > -grygorii