linux-kernel - Re: [PATCH 4/4] ARM: timer-sp: Set dynamic irq affinity

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Date:	Wed, 27 Feb 2013 10:29:11 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Santosh Shilimkar <santosh.shilimkar@...com>
Cc:	Daniel Lezcano <daniel.lezcano@...aro.org>, john.stultz@...aro.org,
	tglx@...utronix.de, jacob.jun.pan@...ux.intel.com,
	linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linaro-kernel@...ts.linaro.org,
	patches@...aro.org, linus.walleij@...ricsson.com
Subject: Re: [PATCH 4/4] ARM: timer-sp: Set dynamic irq affinity

On 27 February 2013 10:26, Santosh Shilimkar <santosh.shilimkar@...com> wrote:
> On Wednesday 27 February 2013 03:47 AM, Daniel Lezcano wrote:
>>
>> From: Viresh Kumar <viresh.kumar@...aro.org>
>>
>> When a cpu goes to a deep idle state where its local timer is shutdown, it
>> notifies the time frame work to use the broadcast timer instead.
>>
>> Unfortunately, the broadcast device could wake up any CPU, including an
>> idle one
>> which is not concerned by the wake up at all.
>>
> Broad-cast device will only open the CPU for which the timer IRQ
> affined to. And infact with subject series the affinity also is
> updated for the CPU which owns the last timer expiry event.
>
> What am I missing here ?

Dynamic affinity will work only if the following flag is set for a
clock_event_device: CLOCK_EVT_FEAT_DYNIRQ, otherwise wakeup
would happen on the cpu to which static affinity was set to.
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