From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422819AbcBQMVl (ORCPT ); Wed, 17 Feb 2016 07:21:41 -0500 Received: from foss.arm.com ([217.140.101.70]:60231 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1422802AbcBQMVi (ORCPT ); Wed, 17 Feb 2016 07:21:38 -0500 Subject: Re: [PATCH v3 4/5] ACPI / processor_idle : introduce ARCH_SUPPORTS_ACPI_PROCESSOR_CSTATE To: "Rafael J. Wysocki" References: <1449065446-26115-1-git-send-email-sudeep.holla@arm.com> <1449065446-26115-5-git-send-email-sudeep.holla@arm.com> <12469811.iv3SctjXxl@vostro.rjw.lan> Cc: Sudeep Holla , linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, x86@kernel.org, Al Stone , Lorenzo Pieralisi , Mahesh Sivasubramanian , Ashwin Chaugule , Prashanth Prakash From: Sudeep Holla Organization: ARM Message-ID: <56C465CE.50403@arm.com> Date: Wed, 17 Feb 2016 12:21:34 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <12469811.iv3SctjXxl@vostro.rjw.lan> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16/02/16 20:18, Rafael J. Wysocki wrote: > On Wednesday, December 02, 2015 02:10:45 PM Sudeep Holla wrote: >> ACPI 6.0 adds a new method to specify the CPU idle states(C-states) >> called Low Power Idle(LPI) states. Since new architectures like ARM64 >> use only LPIs, introduce ARCH_SUPPORTS_ACPI_PROCESSOR_CSTATE to >> encapsulate all the code supporting the old style C-states(_CST) > > No. > > The way it really should work is to check if the firmware supports LPI > (and what kind of it) and try to use _CST if LPI is not supported. > Agreed > If LPI is supported by the firmware, use it if the LPI objects are > present as expected or fall back to using _CST otherwise. > I have something similar but I need to reverse the order I think. > This way it all should work without any new Kconfig options. > I agree with you in terms of avoiding new Kconfig option. However the main reason for adding it is to avoid declaring dummy functions and variables on ARM64. It's hard to justify the maintainers as it's totally useless on ARM64. E.g. boot_option_idle_override, IDLE_NOMWAIT, acpi_unlazy_tlb, arch_safe_halt. Other option is to push those under CONFIG_X86, but then I don't have much idea on what are all needed for IA64, so took an option that encapsulates everything under CSTATE feature Kconfig, which is not user visible and selected by archs supporting it by default. I am open to any other alternative. -- Regards, Sudeep