Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753423AbbFDM3B (ORCPT ); Thu, 4 Jun 2015 08:29:01 -0400 Received: from mail-pa0-f44.google.com ([209.85.220.44]:33728 "EHLO mail-pa0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752671AbbFDM27 (ORCPT ); Thu, 4 Jun 2015 08:28:59 -0400 Message-ID: <5570447D.3020705@linaro.org> Date: Thu, 04 Jun 2015 20:28:45 +0800 From: Hanjun Guo User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Lorenzo Pieralisi CC: Tomasz Nowicki , Will Deacon , Bjorn Helgaas , Arnd Bergmann , Catalin Marinas , "Rafael J. Wysocki" , Jiang Liu , Liviu Dudau , Thomas Gleixner , Yijing Wang , "suravee.suthikulpanit@amd.com" , "msalter@redhat.com" , "linux-pci@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-acpi@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linaro-acpi@lists.linaro.org" Subject: Re: [PATCH 05/11] x86, pci, acpi: Move arch-agnostic MMCONFIG (aka ECAM) and ACPI code out of arch/x86/ directory References: <1432644564-24746-1-git-send-email-hanjun.guo@linaro.org> <1432644564-24746-6-git-send-email-hanjun.guo@linaro.org> <20150526170817.GU1565@arm.com> <55657B02.5090805@linaro.org> <20150602133215.GC23650@red-moon> <55701A31.808@linaro.org> <20150604102253.GA31773@red-moon> In-Reply-To: <20150604102253.GA31773@red-moon> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4784 Lines: 106 On 2015年06月04日 18:22, Lorenzo Pieralisi wrote: > Hi Hanjun, > > On Thu, Jun 04, 2015 at 10:28:17AM +0100, Hanjun Guo wrote: >> Hi Lorenzo, >> >> On 2015???06???02??? 21:32, Lorenzo Pieralisi wrote: >>> On Wed, May 27, 2015 at 09:06:26AM +0100, Tomasz Nowicki wrote: >>>> On 26.05.2015 19:08, Will Deacon wrote: >>>>> On Tue, May 26, 2015 at 01:49:18PM +0100, Hanjun Guo wrote: >>>>>> From: Tomasz Nowicki >>>>>> >>>>>> ECAM standard and MCFG table are architecture independent and it makes >>>>>> sense to share common code across all architectures. Both are going to >>>>>> corresponding files - ecam.c and mcfg.c >>>>>> >>>>>> While we are here, rename pci_parse_mcfg to acpi_parse_mcfg. >>>>>> We already have acpi_parse_mcfg prototype which is used nowhere. >>>>>> At the same time, we need pci_parse_mcfg been global so acpi_parse_mcfg >>>>>> can be used perfectly here. >>>>>> >>>>>> Signed-off-by: Tomasz Nowicki >>>>>> Signed-off-by: Hanjun Guo >>>>>> Tested-by: Suravee Suthikulpanit >>>>>> --- >>>>>> arch/x86/Kconfig | 3 + >>>>>> arch/x86/include/asm/pci_x86.h | 33 ------ >>>>>> arch/x86/pci/acpi.c | 1 + >>>>>> arch/x86/pci/mmconfig-shared.c | 244 +--------------------------------------- >>>>>> arch/x86/pci/mmconfig_32.c | 1 + >>>>>> arch/x86/pci/mmconfig_64.c | 1 + >>>>>> arch/x86/pci/numachip.c | 1 + >>>>>> drivers/acpi/Makefile | 1 + >>>>>> drivers/acpi/mcfg.c | 57 ++++++++++ >>>>>> drivers/pci/Kconfig | 7 ++ >>>>>> drivers/pci/Makefile | 5 + >>>>>> drivers/pci/ecam.c | 245 +++++++++++++++++++++++++++++++++++++++++ >>>>> >>>>> Why can't we make use of the ECAM implementation used by pci-host-generic >>>>> and drivers/pci/access.c? >>>> >>>> We had that question when I had posted MMCFG patch set separately, >>>> please see: >>>> https://lkml.org/lkml/2015/3/11/492 >>> >>> Yes, but the real question is, why do we need to have PCI config space >>> up and running before a bus struct is even created ? I think the reason is >>> the PCI configuration address space format (ACPI 6.0, Table 5-27, page >>> 108): >>> >>> "PCI Configuration space addresses must be confined to devices on >>> PCI Segment Group 0, bus 0. This restriction exists to accommodate >>> access to fixed hardware prior to PCI bus enumeration". >>> >>> On HW reduced platforms I do not even think this is required at all, >>> we have to look into this to avoid code duplication that might well >>> turn out useless. >> >> This is only for the fixed hardware, which will be not available for >> ARM64 (reduced hardware mode), but in Generic Hardware Programming >> Model, we using OEM-provided ACPI Machine Language (AML) code to access >> generic hardware registers, this will be available for reduced hardware >> too. >> >> So in ACPI spec, it says: (ACPI 6.0 page 66, last paragraph) >> >> ACPI defines eight address spaces that may be accessed by generic >> hardware implementations. These include: >> * System I/O space >> * System memory space >> * PCI configuration space >> * Embedded controller space >> * System Management Bus (SMBus) space >> * CMOS >> * PCI BAR Target >> * IPMI space >> >> So if any device using the PCI address space for control, such >> as a system reset control device, its address space can be reside >> in PCI configuration space (who can prevent a OEM do that crazy >> thing? :) ), and it should be accessible before the PCI bus is >> created. > > Us, by changing attitude and questioning features whose usefulness > is questionable. I will look into this and raise the point, I am not > thrilled by the idea of adding another set of PCI accessor functions > and drivers because we have to access a register through PCI before > enumerating the bus (and on arm64 this is totally useless since > we are not meant to support fixed HW anyway). Maybe we can make acpica > code use a "special" stub (ACPI specific, PCI configuration space address > space has restrictions anyway), I have to review this set in its > entirety to see how to do that (and I would kindly ask you to do > it too, before saying it is not possible to implement it). I'm willing to do that, actually, if we don't need a mechanism to access PCI config space before the bus is created, the code can be simplified a lot. Thanks for your help and patient. Hanjun -- 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/