From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hanjun Guo Subject: Re: [Linaro-acpi] [RFC part1 PATCH 1/7] ACPI: Make ACPI core running without PCI on ARM64 Date: Mon, 09 Dec 2013 12:12:24 +0800 Message-ID: <52A54328.3000709@linaro.org> References: <1386088611-2801-1-git-send-email-hanjun.guo@linaro.org> <201312052304.22302.arnd@arndb.de> <52A1E794.1040008@linaro.org> <201312061823.26481.arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mail-pd0-f174.google.com ([209.85.192.174]:43089 "EHLO mail-pd0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760547Ab3LIENE (ORCPT ); Sun, 8 Dec 2013 23:13:04 -0500 Received: by mail-pd0-f174.google.com with SMTP id y13so4444435pdi.33 for ; Sun, 08 Dec 2013 20:13:03 -0800 (PST) In-Reply-To: <201312061823.26481.arnd@arndb.de> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Arnd Bergmann , Tomasz Nowicki Cc: Mark Rutland , Matthew Garrett , linaro-kernel@lists.linaro.org, Russell King - ARM Linux , patches@linaro.org, Olof Johansson , Catalin Marinas , Linus Walleij , Daniel Lezcano , "Rafael J. Wysocki" , linux-kernel@vger.kernel.org, Will Deacon , linaro-acpi@lists.linaro.org, linux-acpi@vger.kernel.org, Rob Herring , Bjorn Helgaas , linux-arm-kernel@lists.infradead.org On 2013-12-7 1:23, Arnd Bergmann wrote: > On Friday 06 December 2013, Tomasz Nowicki wrote: >> On 05.12.2013 23:04, Arnd Bergmann wrote: >>> On Wednesday 04 December 2013, Hanjun Guo wrote: >>>> On 2013=E5=B9=B412=E6=9C=8804=E6=97=A5 00:41, Matthew Garrett wrot= e: >>>>> Given the number of #ifdefs you're adding, wouldn't it make more = sense >>>>> to just add stub functions to include/linux/pci.h? >>>> >>>> Thanks for the suggestion :) >>>> >>>> I can add stub functions in include/linux/pci.h for raw_pci_read()= / >>>> raw_pci_write(), then can remove #ifdefs for acpi_os_read/write_pc= i_configuration(). >>> >>> Actually I wonder about the usefulness of this patch in either form= : Since ACPI >>> on ARM64 is only for servers, I would very much expect them to alwa= ys come with >>> PCI, either physical host bridges with attached devices, or logical= PCI functions >>> used to describe the on-SoC I/O devices. Even in case of virtual ma= chines, you'd >>> normally use PCI as the method to communicate data about the virtio= channels. >>> >>> Can you name a realistic use-case where you'd want ACPI but not PCI= ? >> >> Yes you can describe SoC I/O devices using logical PCI functions onl= y if=20 >> they are on PCI, correct me if I am wrong. Also, devices can be plac= ed=20 >> only on IOMEM (like for ARM SoC) and it is hard to predict which way= =20 >> vendors chose. So way don't let it be configurable? ACPI spec says=20 >> nothing like PCI is needed for ACPI, AFAIK. >=20 > You are right that today's ARM SoCs basically never use PCI to descri= be > internal devices (IIRC VIA VT8500 is an exception, but their PCI was > just a software fabrication). >=20 > However, when we're talking about ACPI on ARM64, that is nothing like= classic > ARM SoCs: As Jon Masters mentioned, this is about new server hardware= following > a (still secret, but hopefully not much longer) hardware specificatio= n that is > explicitly designed to allow interoperability between vendors, so the= y > must have put some thought into how to make the hardware discoverable= =2E It > seems that they are modeling things after how it's done on x86, and t= he > only sensible way to have discoverable hardware there is PCI. This is > also what all x86 SoCs do. I think the concern here is that ACPI is only for server platform or no= t. Since ACPI has lots of content related to power management, I think ACP= I can be used for mobile devices and other platform too, not only for ARM servers, and with this patch, we can support both requirement. Thanks Hanjun -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html