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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 CBFAFC33CB3 for ; Tue, 28 Jan 2020 15:01:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A89832467E for ; Tue, 28 Jan 2020 15:01:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726444AbgA1PBk (ORCPT ); Tue, 28 Jan 2020 10:01:40 -0500 Received: from lhrrgout.huawei.com ([185.176.76.210]:2319 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726243AbgA1PBj (ORCPT ); Tue, 28 Jan 2020 10:01:39 -0500 Received: from LHREML713-CAH.china.huawei.com (unknown [172.18.7.106]) by Forcepoint Email with ESMTP id 5BFBE50E8A17CDAF3232; Tue, 28 Jan 2020 14:46:08 +0000 (GMT) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by LHREML713-CAH.china.huawei.com (10.201.108.36) with Microsoft SMTP Server (TLS) id 14.3.408.0; Tue, 28 Jan 2020 14:46:07 +0000 Received: from [127.0.0.1] (10.202.226.43) 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 15.1.1713.5; Tue, 28 Jan 2020 14:46:07 +0000 Subject: Re: [PATCH RFC 2/2] soc: Add a basic ACPI generic driver To: Arnd Bergmann CC: "Rafael J. Wysocki" , Len Brown , , Olof Johansson , "linux-kernel@vger.kernel.org" , "ACPI Devel Maling List" , Hanjun Guo , gregkh References: <1580210059-199540-1-git-send-email-john.garry@huawei.com> <1580210059-199540-3-git-send-email-john.garry@huawei.com> From: John Garry Message-ID: <683fc9df-3655-5044-f81c-00e2896a268d@huawei.com> Date: Tue, 28 Jan 2020 14:46:07 +0000 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: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.202.226.43] X-ClientProxiedBy: lhreml732-chm.china.huawei.com (10.201.108.83) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28/01/2020 12:50, Arnd Bergmann wrote: Hi Arnd, > On Tue, Jan 28, 2020 at 12:18 PM John Garry wrote: >> >> Add a generic driver for platforms which populate their ACPI PPTT >> processor package ID Type Structure according to suggestion in the ACPI >> spec - see ACPI 6.2, section 5.2.29.3 ID structure Type 2. >> >> The soc_id is from member LEVEL_2_ID. >> >> For this, we need to use a whitelist of platforms which are known to >> populate the structure as suggested. >> >> For now, only the vendor and soc_id fields are exposed. >> >> Signed-off-by: John Garry > > Would it be possible to make this the root device for all on-chip devices > to correctly reflect the hierarchy inside of the soc? I don't think so. The information about the SoC is got from the PPTT, which only describes processors, caches, and physical package boundaries. It doesn't include references to on-chip devices. Having said that (and unrelated to this series), we could add /sys/devices/system/soc folder, similar to node folder. > >> +/* >> + * Known platforms that fill in PPTT package ID structures according to >> + * ACPI spec examples, that being: >> + * - Custom driver attribute is in ID Type Structure VENDOR_ID member >> + * - SoC id is in ID Type Structure LEVEL_2_ID member >> + * See ACPI SPEC 6.2 Table 5-154 for PPTT ID Type Structure >> + */ >> +static struct acpi_platform_list plat_list[] = { >> + {"HISI ", "HIP08 ", 0, ACPI_SIG_PPTT, all_versions}, >> + { } /* End */ >> +}; > > That matches a single machine, right? It doesn't seem very generic > that way. Yes :) The problem is that the PPTT ID structure is open to use how the implementer wants, so we can't assume everything/anything implemented according to the spec examples. Maybe we could call it type1 or something like that for platforms which did use the convention in the spec example. > >> +struct acpi_generic_soc_struct { >> + struct soc_device_attribute dev_attr; >> + u32 vendor; >> +}; >> + >> +static ssize_t vendor_show(struct device *dev, >> + struct device_attribute *attr, >> + char *buf) >> +{ >> + struct acpi_generic_soc_struct *soc = dev_get_drvdata(dev); >> + u8 vendor_id[5] = {}; >> + >> + *(u32 *)vendor_id = soc->vendor; >> + >> + return sprintf(buf, "%s\n", vendor_id); >> +} > > I'd rather not see nonstandard attributes in a "generic" driver at > all. Maybe the > you can simply concatenate the vendor and LEVEL_2_ID into a single string > here? I actually don't really require the vendor attr. And since "vendor" is not in the set of standard soc driver attrs, it can just be omitted. > >> + soc = kzalloc(sizeof(*soc), GFP_KERNEL); >> + if (!soc) >> + return -ENOMEM; >> + >> + soc_dev_attr = &soc->dev_attr; >> + soc_dev_attr->soc_id = kasprintf(GFP_KERNEL, "%s", >> + soc_id); > > On the other hand, it would make sense to fill out additional fields here. > You have already matched the name of the board from the > acpi_platform_list, so there are two strings available that could be put > into the "machine" field, and it would make sense to fill out "family" with > something that identifies it as coming from ACPI PPTT data. OK, maybe the ones you suggested could be added. I did just want to start out with a minimal sets of files, especially since we don't always have a direct mapping between soc driver attrs and this PPTT ID structure. Thanks, John