From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751164AbdFBJj1 (ORCPT ); Fri, 2 Jun 2017 05:39:27 -0400 Received: from foss.arm.com ([217.140.101.70]:37776 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750813AbdFBJjZ (ORCPT ); Fri, 2 Jun 2017 05:39:25 -0400 Cc: Sudeep Holla , leo.yan@linaro.org, "open list:CPUIDLE DRIVERS" , open list Subject: Re: [PATCH V2] ARM: cpuidle: Support asymmetric idle definition To: Daniel Lezcano , rjw@rjwysocki.net, lorenzo.pieralisi@arm.com References: <1496317188-15272-1-git-send-email-daniel.lezcano@linaro.org> <3ec88de3-7d18-0ea6-bc27-e98084f2b6f6@arm.com> <4fe4558f-5881-11dc-5d36-93c92a272eed@linaro.org> From: Sudeep Holla Organization: ARM Message-ID: Date: Fri, 2 Jun 2017 10:39:21 +0100 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: <4fe4558f-5881-11dc-5d36-93c92a272eed@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/06/17 10:25, Daniel Lezcano wrote: > 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 ? > The bindings are upstream right. Not all DTS are upstream, firmware generate them especially for large systems. Check arch/arm64/boot/dts/cavium/thunder{,2}-{88,99}xx.dtsi, it has supports PSCI and firmware can update DTB to add the idle states. They are systems with 96 and 128 CPUs. -- Regards, Sudeep