linux-kernel - Re: [RFC PATCH 0/5] clockevents: decouple broadcast mechanism from drivers

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Message-ID: <20130102114148.GB25907@e106331-lin.cambridge.arm.com>
Date:	Wed, 2 Jan 2013 11:41:48 +0000
From:	Mark Rutland <mark.rutland@....com>
To:	Santosh Shilimkar <santosh.shilimkar@...com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"nico@...aro.org" <nico@...aro.org>,
	Marc Zyngier <Marc.Zyngier@....com>,
	Will Deacon <Will.Deacon@....com>,
	"john.stultz@...aro.org" <john.stultz@...aro.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH 0/5] clockevents: decouple broadcast mechanism from
 drivers

On Fri, Dec 21, 2012 at 10:08:02AM +0000, Santosh Shilimkar wrote:
> Mark,
> 
> On Tuesday 18 December 2012 05:36 PM, Mark Rutland wrote:
> > In some SMP systems, cpu-local timers may stop delivering interrupts
> > when in low power states, or not all CPUs may have local timers. To
> > support these systems we have a mechanism for broadcasting timer ticks
> > to other CPUs. This mechanism relies on the struct
> > clock_event_device::broadcast function pointer, which is a
> > driver-specific mechanism for broadcasting ticks to other CPUs.
> >
> > As the broadcast mechanism is architecture-specific, placing the
> > broadcast function on struct clock_event_device ties each driver to a
> > single architecture. Additionally the driver or architecture backend
> > must handle the routing of broadcast ticks to the correct
> > clock_event_device, leading to duplication of the list of active
> > clock_event_devices.
> >
> > These patches introduce a generic mechanism for handling the receipt of
> > timer broadcasts, and an optional architecture-specific broadcast
> > function which allows drivers to be decoupled from a particular
> > architecture will retaining support for timer tick broadcasts. These
> > mechanisms are wired up for the arm port, and have been boot-tested on a
> > pandaboard.
> >
> Apart from the relevant comments given against couple of patches and
> Stephen's printk string comment, the series looks pretty good to me.
> 
> I have tested the series with CPUIdle where the broadcast is actually
> used actively.

Great!

> So feel free to add,
> Reviewed-tested-by: Santosh Shilimkar <santosh.shilimkar@...com>

Thanks!

Mark.

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