linux-kernel - Re: [PATCHv2 0/4] clockevents: decouple broadcast mechanism from drivers

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Message-ID: <20130110094435.GA17741@e106331-lin.cambridge.arm.com>
Date:	Thu, 10 Jan 2013 09:44:44 +0000
From:	Mark Rutland <mark.rutland@....com>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"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: [PATCHv2 0/4] clockevents: decouple broadcast mechanism from
 drivers

On Wed, Jan 09, 2013 at 08:46:18PM +0000, Stephen Boyd wrote:
> On 01/09/13 06:46, Mark Rutland wrote:
> > This is an updated version of the series I posted back in December:
> > http://lists.infradead.org/pipermail/linux-arm-kernel/2012-December/137929.html
> >
> > Changes since v1:
> > * Drop removal of guards in smp.c
> > * Removed useless evt->evt_handler check in tick_receive_broadcast
> > * Fix up tick_receive_broadcast when !GENERIC_CLOCKEVENTS_BROADCAST
> > * Fix checkpatch issues (multi-line strings)
> >
> > Thanks go to Stephen Boyd and Santosh Shilimkar for their commments.
> >
> > 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.
> >
> 
> For the series:
> 
> Reviewed-by: Stephen Boyd <sboyd@...eaurora.org>

Thanks!

> 
> -- 
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> hosted by The Linux Foundation
> 
> 

Mark.

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