From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B7E87C433E0 for ; Thu, 21 May 2020 14:01:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 836E320721 for ; Thu, 21 May 2020 14:01:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729547AbgEUOBQ (ORCPT ); Thu, 21 May 2020 10:01:16 -0400 Received: from lhrrgout.huawei.com ([185.176.76.210]:2238 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729532AbgEUOBQ (ORCPT ); Thu, 21 May 2020 10:01:16 -0400 Received: from lhreml724-chm.china.huawei.com (unknown [172.18.7.107]) by Forcepoint Email with ESMTP id 3CC2F38420F11539B82D; Thu, 21 May 2020 15:01:14 +0100 (IST) Received: from [127.0.0.1] (10.47.6.132) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1913.5; Thu, 21 May 2020 15:01:13 +0100 Subject: Re: [PATCH V1 RESEND 1/3] perf/imx_ddr: Add system PMU identifier for userspace To: Will Deacon , Rob Herring CC: Joakim Zhang , Mark Rutland , Shawn Guo , NXP Linux Team , "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" , , "linux-kernel@vger.kernel.org" References: <20200512073115.14177-1-qiangqing.zhang@nxp.com> <20200512073115.14177-2-qiangqing.zhang@nxp.com> <20200519185125.GB453195@bogus> <20200520073304.GA23534@willie-the-truck> <20200521130415.GB5949@willie-the-truck> From: John Garry Message-ID: Date: Thu, 21 May 2020 15:00:13 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.1.2 MIME-Version: 1.0 In-Reply-To: <20200521130415.GB5949@willie-the-truck> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.47.6.132] X-ClientProxiedBy: lhreml715-chm.china.huawei.com (10.201.108.66) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 21/05/2020 14:04, Will Deacon wrote: > On Wed, May 20, 2020 at 09:23:41AM -0600, Rob Herring wrote: >> On Wed, May 20, 2020 at 1:33 AM Will Deacon wrote: >>> >>> On Tue, May 19, 2020 at 12:51:25PM -0600, Rob Herring wrote: >>>> On Tue, May 12, 2020 at 03:31:13PM +0800, Joakim Zhang wrote: >>>>> +static ssize_t ddr_perf_identifier_show(struct device *dev, >>>>> + struct device_attribute *attr, >>>>> + char *page) >>>>> +{ >>>>> + struct ddr_pmu *pmu = dev_get_drvdata(dev); >>>>> + >>>>> + return sprintf(page, "%s\n", pmu->devtype_data->identifier); >>>> >>>> Why do we need yet another way to identify the SoC from userspace? >>> >>> I also really dislike this. What's the preferred way to identify the SoC >>> from userspace? >> >> /proc/cpuinfo? ;) > > The *SoC*! > >> For an non-firmware specific case, I'd say soc_device should be. I'd >> guess ACPI systems don't use it and for them it's dmidecode typically. >> The other problem I have with soc_device is it is optional. > Hi Will, > John -- what do you think about using soc_device to expose this information, > with ACPI systems using DMI data instead? Generally I don't think that DMI is reliable, and I saw this as the least preferred choice. I'm looking at the sysfs DMI info for my dev board, and I don't even see anything like a SoC identifier. As for the event_source device sysfs identifier file, it would not always contain effectively the same as the SoC ID. Certain PMUs which I'm interested in plan to have probe-able identification info available in future. Thanks, John