From mboxrd@z Thu Jan 1 00:00:00 1970 From: Preeti U Murthy 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 Message-ID: <52AA9953.9090909@linux.vnet.ibm.com> References: <20131213041901.17199.37383.stgit@preeti.in.ibm.com> <1386911862.15730.81.camel@pasglop> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from e38.co.us.ibm.com ([32.97.110.159]:42561 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750869Ab3LMFYv (ORCPT ); Fri, 13 Dec 2013 00:24:51 -0500 Received: from /spool/local by e38.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 12 Dec 2013 22:24:51 -0700 In-Reply-To: <1386911862.15730.81.camel@pasglop> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Benjamin Herrenschmidt 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 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