From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751301AbdFBJZ1 (ORCPT ); Fri, 2 Jun 2017 05:25:27 -0400 Received: from mail-wm0-f44.google.com ([74.125.82.44]:35350 "EHLO mail-wm0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751124AbdFBJZY (ORCPT ); Fri, 2 Jun 2017 05:25:24 -0400 Subject: Re: [PATCH V2] ARM: cpuidle: Support asymmetric idle definition To: Sudeep Holla , rjw@rjwysocki.net, lorenzo.pieralisi@arm.com Cc: leo.yan@linaro.org, "open list:CPUIDLE DRIVERS" , open list References: <1496317188-15272-1-git-send-email-daniel.lezcano@linaro.org> <3ec88de3-7d18-0ea6-bc27-e98084f2b6f6@arm.com> From: Daniel Lezcano Message-ID: <4fe4558f-5881-11dc-5d36-93c92a272eed@linaro.org> Date: Fri, 2 Jun 2017 11:25:16 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 MIME-Version: 1.0 In-Reply-To: <3ec88de3-7d18-0ea6-bc27-e98084f2b6f6@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/06/2017 11:20, Sudeep Holla wrote: > > > On 01/06/17 12:39, Daniel Lezcano wrote: >> Some hardware have clusters with different idle states. The current code does >> not support this and fails as it expects all the idle states to be identical. >> >> Because of this, the Mediatek mtk8173 had to create the same idle state for a >> big.Little system and now the Hisilicon 960 is facing the same situation. >> >> Solve this by simply assuming the multiple driver will be needed for all the >> platforms using the ARM generic cpuidle driver which makes sense because of the >> different topologies we can support with a single kernel for ARM32 or ARM64. >> >> Every CPU has its own driver, so every single CPU can specify in the DT the >> idle states. >> >> This simple approach allows to support the future dynamIQ system, current SMP >> and HMP. >> >> It is unoptimal from a memory point of view for a system with a large number of >> CPUs but nowadays there is no such system with a cpuidle driver on ARM. >> > > While I agree this may be simple solution, but just not necessary for > systems with symmetric idle states especially one with large number of > CPUs. I don't like to see 96 CPU Idle driver on say ThunderX. So we > *must* have some basic distinction done here. > > IMO, we can't punish a large SMP systems just because they don't have > asymmetric idle states. Can you point me in the upstream kernel a DTS with 96 cpus and using the cpuidle-arm driver ? -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog