From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e32.co.us.ibm.com (e32.co.us.ibm.com [32.97.110.150]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e32.co.us.ibm.com", Issuer "GeoTrust SSL CA" (not verified)) by ozlabs.org (Postfix) with ESMTPS id 9042B2C00AE for ; Fri, 13 Dec 2013 16:24:52 +1100 (EST) Received: from /spool/local by e32.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 12 Dec 2013 22:24:50 -0700 Received: from b03cxnp08027.gho.boulder.ibm.com (b03cxnp08027.gho.boulder.ibm.com [9.17.130.19]) by d03dlp01.boulder.ibm.com (Postfix) with ESMTP id 4F6541FF001B for ; Thu, 12 Dec 2013 22:24:24 -0700 (MST) Received: from d03av05.boulder.ibm.com (d03av05.boulder.ibm.com [9.17.195.85]) by b03cxnp08027.gho.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id rBD3Mqjg7733662 for ; Fri, 13 Dec 2013 04:22:52 +0100 Received: from d03av05.boulder.ibm.com (localhost [127.0.0.1]) by d03av05.boulder.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id rBD5OjR2015441 for ; Thu, 12 Dec 2013 22:24:47 -0700 Message-ID: <52AA9953.9090909@linux.vnet.ibm.com> Date: Fri, 13 Dec 2013 10:51:23 +0530 From: Preeti U Murthy MIME-Version: 1.0 To: Benjamin Herrenschmidt Subject: Re: [RFC PATCH] time: Support in tick broadcast framework for archs without an external wakeup source References: <20131213041901.17199.37383.stgit@preeti.in.ibm.com> <1386911862.15730.81.camel@pasglop> In-Reply-To: <1386911862.15730.81.camel@pasglop> Content-Type: text/plain; charset=ISO-8859-1 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 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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