[PATCH] ARM: formalize an IPI for CPU wake-ups

[Kukjin Kim]

Colin Cross wrote:
> 
> On Wed, Aug 1, 2012 at 2:42 AM, Kukjin Kim <kgene.kim at samsung.com> wrote:
> > Stephen Boyd wrote:
> >>
> >> On 07/10/12 23:34, Kukjin Kim wrote:
> >> > Stephen Boyd wrote:
> >> >> Great. Kukjin Kim, can exynos use SGI0? It looks like exynos is the
> >> only
> >> >> one left to move to SGI0.
> >> >>
> >> > Yeah, EXYNOS can use SGI0 instead of SGI1 :)
> >> >
> >> >
> >>
> >> Russell, can we apply something like this?
> >>
> > Please feel free to add my ack on following change.
> >
> > Acked-by: Kukjin Kim <kgene.kim at samsung.com>
> >
> 
> When testing coupled cpuidle on Exynos5, I found that sending an IPI
> does not successfully wake up CPU1.  CPU1 is in a wfe with interrupts
> masked, not a wfi, so an interrupt is not able to wake it up.  It
> tends to wake up anyways because the next time a spin lock is
> unlocked, often during a timer interrupt on CPU0, CPU0 executes an sev
> which wakes up CPU1.  You can see that the IPI is unnecessary by
> removing the gic_raise_softirq and replacing it with dsb_sev().

Hmm...could be. Let me check you commented in detail. And if any updates,
I'll let you know.

Thanks for your information.

Best regards,
Kgene.
--
Kukjin Kim <kgene.kim at samsung.com>, Senior Engineer,
SW Solution Development Team, Samsung Electronics Co., Ltd.