Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932452AbaJ2Knh (ORCPT ); Wed, 29 Oct 2014 06:43:37 -0400 Received: from service87.mimecast.com ([91.220.42.44]:53112 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932259AbaJ2Knf convert rfc822-to-8bit (ORCPT ); Wed, 29 Oct 2014 06:43:35 -0400 Date: Wed, 29 Oct 2014 10:43:22 +0000 From: Lorenzo Pieralisi To: Hanjun Guo Cc: Catalin Marinas , "Rafael J. Wysocki" , Mark Rutland , Olof Johansson , "grant.likely@linaro.org" , Will Deacon , "graeme.gregory@linaro.org" , Arnd Bergmann , Sudeep Holla , "jcm@redhat.com" , Jason Cooper , Marc Zyngier , Bjorn Helgaas , Daniel Lezcano , Mark Brown , Rob Herring , Robert Richter , Lv Zheng , Robert Moore , Liviu Dudau , Randy Dunlap , Charles Garcia-Tobin , "Kangkang.Shen@huawei.com" , "linux-acpi@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linaro-acpi@lists.linaro.org" Subject: Re: [PATCH v5 12/18] ACPI / processor: Make it possible to get CPU hardware ID via GICC Message-ID: <20141029104321.GA8896@e102568-lin.cambridge.arm.com> References: <1413553034-20956-1-git-send-email-hanjun.guo@linaro.org> <1413553034-20956-13-git-send-email-hanjun.guo@linaro.org> <20141024173920.GB8303@red-moon> <544E1732.5090902@linaro.org> MIME-Version: 1.0 In-Reply-To: <544E1732.5090902@linaro.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-OriginalArrivalTime: 29 Oct 2014 10:43:30.0091 (UTC) FILETIME=[2DB1D7B0:01CFF365] X-MC-Unique: 114102910433205001 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 27, 2014 at 09:58:10AM +0000, Hanjun Guo wrote: [...] > >> +static int map_gicc_mpidr(struct acpi_subtable_header *entry, > >> + int device_declaration, u32 acpi_id, int *mpidr) > >> +{ > >> + struct acpi_madt_generic_interrupt *gicc = > >> + container_of(entry, struct acpi_madt_generic_interrupt, header); > >> + > >> + if (!(gicc->flags & ACPI_MADT_ENABLED)) > >> + return -ENODEV; > >> + > >> + /* In the GIC interrupt model, logical processors are > >> + * required to have a Processor Device object in the DSDT, > >> + * so we should check device_declaration here > >> + */ > >> + if (device_declaration && (gicc->uid == acpi_id)) { > >> + /* > >> + * Only bits [0:7] Aff0, bits [8:15] Aff1, bits [16:23] Aff2 > >> + * and bits [32:39] Aff3 are meaningful, so pack the Affx > >> + * fields into a single 32 bit identifier to accommodate the > >> + * acpi processor drivers. > >> + */ > >> + *mpidr = ((gicc->arm_mpidr & 0xff00000000) >> 8) > >> + | gicc->arm_mpidr; > > > > The simple fact that you define a function to pack the mpidr value and > > you can't use it here because this is *generic* code is telling, and > > a very bad omen. At the cost of sounding like a broken record, I do not > > like this mpidr->apic->logical_cpu song and dance at all. > > ACPI is peppered with code (eg hotplug is another example, CPUidle driver > > even worse) that is supposed to be generic but contains x86 code to carry > > out this cpuid conversion, I really think that in order to start an ARM64 > > ACPI port properly we should at least try to factor out this physical to > > logical cpu id conversion, and it is not the first time that I mention this > > on the lists. > > I know, thanks for pointing this out. As I replied in previous version > of this patch set, apic_id is x86/ia64 specific, but the meaning behind > it is not. It means the CPU hardware id to identify itself in the system, > it just like MPIDR on ARM. Yes, except that it is called apic_id. > I will send out a patch for RFC to convert apic_id to physid which > is generic for all platforms. That seems a good idea to sound out if I am the only one having an issue with the current approach. > > I will also talk to Rafael about this at the earliest opportunity, I > > guess that x86 code relies on apic-id because some ACPI versions could > > not rely on the acpi-id or some other reasons I have to investigate. > > As ACPI spec (section 8.4, Declaring Processors) said, Each processor > in the system must be declared in the ACPI namespace, so each cpu will > have acpi_id in all ACPI versions, and in theory we can map acpi_id to > logical cpu id if we want to. > > But things are complicated, apic_id is connected to many > tables, MADT for smp init, DSDT for device driver, and SRAT for NUMA (there > is no acpi_id in it, ONLY has apic_id in the table for x86/ia64), so if we > want to factor the code to map acpi_id to logical cpu id, we need to modify: > > - ACPI drivers; > - SMP init for x86 and ia64 > - the mappings for NUMA init for x86 and ia64 > that will be lots of work I think. > > I'm willing to discuss this further and come out a solution, please > comment on what I said and share your ideas :) Factoring out apic_id to a common cpu_physical_id is ok to me, because basically that's what you are doing except for the naming. I do not have any particular preference for the acpi_id, I mentioned that only as a means to implement a generic cpu_physical_id, arch agnostic. Drop the RFC you mentioned above please on the list, we will restart debating from there. Thanks, Lorenzo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/