From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753025AbbJNJD6 (ORCPT ); Wed, 14 Oct 2015 05:03:58 -0400 Received: from eu-smtp-delivery-143.mimecast.com ([146.101.78.143]:64690 "EHLO eu-smtp-delivery-143.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751559AbbJNJDz convert rfc822-to-8bit (ORCPT ); Wed, 14 Oct 2015 05:03:55 -0400 Subject: Re: [PATCH v3 24/24] arm64: cpuinfo: Expose MIDR_EL1 and REVIDR_EL1 to sysfs To: linux-arm-kernel@lists.infradead.org References: <1444756952-31145-1-git-send-email-suzuki.poulose@arm.com> <1444756952-31145-25-git-send-email-suzuki.poulose@arm.com> Cc: catalin.marinas@arm.com, will.deacon@arm.com, mark.rutland@arm.com, dave.martin@arm.com, Vladimir.Murzin@arm.com, steve.capper@linaro.org, linux-kernel@vger.kernel.org, ard.biesheuvel@linaro.org, james.morse@arm.com, marc.zyngier@arm.com, christoffer.dall@linaro.org, andre.przywara@arm.com, edward.nevill@linaro.org, aph@redhat.com, ryan.arnold@linaro.org From: "Suzuki K. Poulose" Message-ID: <561E1A77.1060902@arm.com> Date: Wed, 14 Oct 2015 10:03:51 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <1444756952-31145-25-git-send-email-suzuki.poulose@arm.com> X-OriginalArrivalTime: 14 Oct 2015 09:03:51.0798 (UTC) FILETIME=[3EEF3960:01D1065F] X-MC-Unique: PHwxJZ_LTaKa9GihTJcVVw-1 Content-Type: text/plain; charset=WINDOWS-1252; format=flowed Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 13/10/15 18:22, Suzuki K. Poulose wrote: > From: Steve Capper > > It can be useful for JIT software to be aware of MIDR_EL1 and > REVIDR_EL1 to ascertain the presence of any core errata that could > affect codegen. > > This patch exposes these registers through sysfs: > > /sys/devices/system/cpu/cpu$ID/identification/midr > /sys/devices/system/cpu/cpu$ID/identification/revidr > > where $ID is the cpu number. For big.LITTLE systems, one can have a > mixture of cores (e.g. Cortex A53 and Cortex A57), thus all CPUs need > to be enumerated. > > If the kernel does not have valid information to populate these entries > with, an empty string is returned to userspace. > For the record: > Signed-off-by: Steve Capper [ Added error code for cpus !present in show_xxx_name ] > Signed-off-by: Suzuki K. Poulose Suzuki