From: Preeti U Murthy <preeti@linux.vnet.ibm.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: peterz@infradead.org, fweisbec@gmail.com,
paul.gortmaker@windriver.com, paulus@samba.org, mingo@kernel.org,
shangw@linux.vnet.ibm.com, rafael.j.wysocki@intel.com,
paulmck@linux.vnet.ibm.com, arnd@arndb.de,
linux-pm@vger.kernel.org, rostedt@goodmis.org,
michael@ellerman.id.au, john.stultz@linaro.org,
tglx@linutronix.de, chenhui.zhao@freescale.com,
deepthi@linux.vnet.ibm.com, r58472@freescale.com,
geoff@infradead.org, linux-kernel@vger.kernel.org,
srivatsa.bhat@linux.vnet.ibm.com, schwidefsky@de.ibm.com,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [RFC PATCH] time: Support in tick broadcast framework for archs without an external wakeup source
Date: Fri, 13 Dec 2013 10:51:23 +0530 [thread overview]
Message-ID: <52AA9953.9090909@linux.vnet.ibm.com> (raw)
In-Reply-To: <1386911862.15730.81.camel@pasglop>
Hi Ben,
On 12/13/2013 10:47 AM, Benjamin Herrenschmidt wrote:
> On Fri, 2013-12-13 at 09:49 +0530, Preeti U Murthy wrote:
>> On some architectures, in certain CPU deep idle states the local timers stop.
>> An external clock device is used to wakeup these CPUs. The kernel support for the
>> wakeup of these CPUs is provided by the tick broadcast framework by using the
>> external clock device as the wakeup source.
>
>> However on architectures like PowerPC there is no external clock device.
>
> Minor nit ...
>
> I wouldn't make this an architectural statement. Some PowerPC's do have
> external clock devices (for example the old MPIC interrupt controller
> had timers). In fact, if we really need it, I'm sure we *could* find
> something somewhere in P8 that could act as a timer, probably hijacking
> a bit of the OCC or similar but at this stage, that's not on the radar.
>
> So make it an implementation statement. "However, not all
> implementations, such as some PowerPC ones, provide such an external
> timer ...".
Thanks for this information. I will update this going ahead.
Regards
Preeti U Murthy
next prev parent reply other threads:[~2013-12-13 5:24 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-13 4:19 [RFC PATCH] time: Support in tick broadcast framework for archs without an external wakeup source Preeti U Murthy
2013-12-13 5:17 ` Benjamin Herrenschmidt
2013-12-13 5:21 ` Preeti U Murthy [this message]
2013-12-16 4:36 ` Preeti U Murthy
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