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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 E3A72C3279B for ; Mon, 2 Jul 2018 10:01:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A4311255D7 for ; Mon, 2 Jul 2018 10:01:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A4311255D7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933912AbeGBKBy (ORCPT ); Mon, 2 Jul 2018 06:01:54 -0400 Received: from foss.arm.com ([217.140.101.70]:56438 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753269AbeGBKBx (ORCPT ); Mon, 2 Jul 2018 06:01:53 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BF52A18A; Mon, 2 Jul 2018 03:01:52 -0700 (PDT) Received: from [10.1.210.28] (e107155-lin.cambridge.arm.com [10.1.210.28]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B712E3F5BA; Mon, 2 Jul 2018 03:01:50 -0700 (PDT) Cc: Sudeep Holla , linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Jeremy Linton , shunyong.yang@hxt-semitech.com, yu.zheng@hxt-semitech.com, catalin.marinas@arm.com, will.deacon@arm.com, Lorenzo Pieralisi , "Rafael J. Wysocki" Subject: Re: [PATCH] ACPI/PPTT: use ACPI ID whenever ACPI_PPTT_ACPI_PROCESSOR_ID_VALID is set To: Andrew Jones References: <1530289077-2444-1-git-send-email-sudeep.holla@arm.com> <20180630071620.gszzib7oha3jn3j2@hawk.localdomain> From: Sudeep Holla Organization: ARM Message-ID: Date: Mon, 2 Jul 2018 11:01:49 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <20180630071620.gszzib7oha3jn3j2@hawk.localdomain> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 30/06/18 08:16, Andrew Jones wrote: > On Fri, Jun 29, 2018 at 05:17:57PM +0100, Sudeep Holla wrote: >> Currently we use the ACPI processor ID only for the leaf/processor nodes >> as the specification states it must match the value of ACPI processor ID >> field in the processor’s entry in the MADT. >> >> However, if a PPTT structure represents processors group, it match a >> processor container UID in the namespace and ACPI_PPTT_ACPI_PROCESSOR_ID_VALID >> flag describe whether the ACPI processor ID is valid. >> >> Lets use UID whenever ACPI_PPTT_ACPI_PROCESSOR_ID_VALID is set to be >> consistent instead of using table offset as it's currently done for non >> leaf nodes. >> >> Cc: "Rafael J. Wysocki" >> Signed-off-by: Sudeep Holla >> --- >> drivers/acpi/pptt.c | 10 ++++++++-- >> 1 file changed, 8 insertions(+), 2 deletions(-) >> >> Hi, >> >> There's ongoing discussion on assigning ID based in OS using simple >> counters. It can never be consistent with firmware's view. So if the >> firmware provides valid UID for non-processors node, we must use it. > > I agree with this. I've been so focused on the fact that the ACPI offsets > are arbitrary, and thus counters can't be worse, that I nearly forgot how > these IDs are actually defined: > Yes, it's platform dependent and I now realize that I never explicitly mentioned that, let alone emphasize on that. I was for UID for the same reason. [...] > > When the valid flag is set we'll now return a [hopefully] correct platform > dependent ID, but when it's not we'll return an ACPI table offset. How > will users of the ID know? Also, it's possible to return -ENOENT for the > ID when calling find_acpi_cpu_topology(). How can we distinguish that from > an arbitrary platform dependent ID? > But why should one need to distinguish that ? Even offset is kind of sparsely distributed UID. -- Regards, Sudeep