linux-kernel - Re: [PATCH V7 08/11] pci, acpi: Support for ACPI based generic PCI host controller

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Date:	Tue, 10 May 2016 19:54:17 +0200
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Tomasz Nowicki <tn@...ihalf.com>
Cc:	Bjorn Helgaas <helgaas@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	Will Deacon <will.deacon@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Hanjun Guo <hanjun.guo@...aro.org>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Sinan Kaya <okaya@...eaurora.org>, jchandra@...adcom.com,
	robert.richter@...iumnetworks.com, mw@...ihalf.com,
	Liviu.Dudau@....com, David Daney <ddaney@...iumnetworks.com>,
	wangyijing@...wei.com,
	Suravee Suthikulanit <Suravee.Suthikulpanit@....com>,
	Mark Salter <msalter@...hat.com>,
	Linux PCI <linux-pci@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>,
	Jon Masters <jcm@...hat.com>, andrea.gallo@...aro.org,
	dhdang@....com, jeremy.linton@....com, liudongdong3@...wei.com,
	Christopher Covington <cov@...eaurora.org>
Subject: Re: [PATCH V7 08/11] pci, acpi: Support for ACPI based generic PCI
 host controller

On Tue, May 10, 2016 at 5:19 PM, Tomasz Nowicki <tn@...ihalf.com> wrote:
> This patch is going to implement generic PCI host controller for
> ACPI world, similar to what pci-host-generic.c driver does for DT world.
>
> All such drivers, which we have seen so far, were implemented within
> arch/ directory since they had some arch assumptions (x86 and ia64).
> However, they all are doing similar thing, so it makes sense to find
> some common code and abstract it into the generic driver.
>
> In order to handle PCI config space regions properly, we define new
> MCFG interface which does sanity checks on MCFG table and keeps its
> root pointer. User is able to lookup MCFG regions based on that root
> pointer and specified domain:bus_start:bus_end touple. We are using
> pci_mmcfg_late_init old prototype to avoid another function name.
>
> The implementation of pci_acpi_scan_root() looks up the MCFG entries
> and sets up a new mapping (regions are not mapped until host controller ask
> for it). Generic PCI functions are used for accessing config space.
> Driver selects PCI_ECAM and uses functions from drivers/pci/ecam.h
> to create and access ECAM mappings.
>
> As mentioned in Kconfig help section, ACPI_PCI_HOST_GENERIC choice
> should be made on a per-architecture basis.
>
> Signed-off-by: Tomasz Nowicki <tn@...ihalf.com>
> Signed-off-by: Jayachandran C <jchandra@...adcom.com>
> ---
>  drivers/acpi/Kconfig            |   8 +++
>  drivers/acpi/Makefile           |   1 +
>  drivers/acpi/pci_mcfg.c         |  97 ++++++++++++++++++++++++++
>  drivers/acpi/pci_root_generic.c | 149 ++++++++++++++++++++++++++++++++++++++++

Why do we need a new file?  Would there be any problem with adding
that code to pci_root.c?