From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752666Ab3LJIpI (ORCPT ); Tue, 10 Dec 2013 03:45:08 -0500 Received: from mail-pd0-f173.google.com ([209.85.192.173]:33968 "EHLO mail-pd0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750789Ab3LJIpF (ORCPT ); Tue, 10 Dec 2013 03:45:05 -0500 Message-ID: <52A6D48A.4000507@linaro.org> Date: Tue, 10 Dec 2013 16:44:58 +0800 From: Alex Shi User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 To: Daniel Lezcano , Frederic Weisbecker , LAK , "tglx@linutronix.de" , "linux-kernel@vger.kernel.org" , preeti@linux.vnet.ibm.com, "len.brown@intel.com" Subject: Re: questions of cpuidle References: <52A5C846.30308@linaro.org> <52A5D0E0.7050201@linaro.org> <52A6B5BB.3060506@linaro.org> <52A6C24B.3030800@linaro.org> In-Reply-To: <52A6C24B.3030800@linaro.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/10/2013 03:27 PM, Daniel Lezcano wrote: > >> And does the wake up pass via GIC to CPU? If so, does the GIC need >> keep awake when all cpu idle? If not, how the firmware give the >> interrupt to CPU? And I am wondering if the deep idle cpu voltage get >> to near 0. How the cpu get the interrupt signal? > > If a deep idle state powers down the GIC, it is up to the PMU to proxy > the interrupts. When an interrupt occurs, the PMU powers up the logic, > including the GIC. The notifier call chain with cpu_suspend / cpu_resume > will save and restore the GIC registers. > > But this is hardware specific and will depend on how the PMU is > implemented and how far it goes in the power management. > > You have a good example in the drivers/cpuidle/cpuidle-ux500.c to > understand with the comments how the interrupts are handled through the > power management unit. > > In the Xillinx documentation available on the web [1], the chapter 24.4 > gives the information about one kind of PMU. > > I believe the mechanism is pretty similar on all the hardware but it is > obfuscated by a generic power instruction like mwait. > > -- Daniel > > [1] > http://www.xilinx.com/support/documentation/user_guides/ug585-Zynq-7000-TRM.pdf > Thanks a lot, Daniel. You are a expert of ARM cpu idle! :) -- Thanks Alex