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From: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
To: Liviu Dudau <Liviu.Dudau@arm.com>
Cc: Rob Herring <robherring2@gmail.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Arnd Bergmann <arnd@arndb.de>, Rob Herring <robh+dt@kernel.org>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Catalin Marinas <Catalin.Marinas@arm.com>,
	Will Deacon <Will.Deacon@arm.com>,
	Russell King <linux@arm.linux.org.uk>,
	linux-pci <linux-pci@vger.kernel.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	Tanmay Inamdar <tinamdar@apm.com>,
	Grant Likely <grant.likely@secretlab.ca>,
	Sinan Kaya <okaya@codeaurora.org>,
	Jingoo Han <jg1.han@samsung.com>,
	Kukjin Kim <kgene.kim@samsung.com>,
	Suravee Suthikulanit <suravee.suthikulpanit@amd.com>,
	linux-arch <linux-arch@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Device Tree ML <devicetree@vger.kernel.org>,
	LAKML <linux-arm-kernel@lists.infradead.org>,
	"grant.likely@linaro.org" <grant.likely@linaro.org>
Subject: Re: [PATCH v10 07/10] OF: Introduce helper function for getting PCI domain_nr
Date: Mon, 8 Sep 2014 10:39:05 -0600	[thread overview]
Message-ID: <20140908163905.GC29679@obsidianresearch.com> (raw)
In-Reply-To: <20140908155931.GP27864@e106497-lin.cambridge.arm.com>

On Mon, Sep 08, 2014 at 04:59:31PM +0100, Liviu Dudau wrote:

> > I don't really understand how domains are used so it's hard to provide
> > a recommendation here. Do domains even belong in the DT?
> 
> ACPI calls them segments and the way Bjorn explained it to me at some moment was
> that it was an attempt to split up a bus in different groups (or alternatively,
> merge a few busses together). To be honest I haven't seen systems where the domain
> is anything other than zero, but JasonG (or maybe Benjamin) were floating an
> idea of using the domain number to identify physical slots.

A PCI domain qualifies the bus:device.function addressing so that we
can have duplicate BDFs in the system.

So, yes, they belong in DT - each 'top level' PCI node naturally
represents a unique set of BDF addressing below it, and could alias
other top level nodes. The first step to resolve a BDF to a DT node is
to find the correct 'top level' by mapping the domain number.

In an ideal world no small scale system should ever have domains. They
were primarily introduced for large scale NUMA system that actually
have more than 256 PCI busses.

However, from a DT prespective, we've been saying that if the SOC
presents a PCI-E root port that shares nothing with other root ports
(ie aperture, driver instance, config space) then those ports must be
represented by unique 'top level' DT nodes, and each DT node must be
assigned to a Linux PCI domain.

IMHO, designing such a SOC ignores the API guidelines provides by the
PCI-E spec itself, and I hope such a thing won't be considered SBSA
compatible..

Jason

  reply	other threads:[~2014-09-08 16:39 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-08 13:54 [PATCH v10 00/10] Support for creating generic PCI host bridges from DT Liviu Dudau
2014-09-08 13:54 ` [PATCH v10 01/10] Fix ioport_map() for !CONFIG_GENERIC_IOMAP cases Liviu Dudau
2014-09-08 13:54 ` [PATCH v10 02/10] PCI: Introduce helper functions to deal with PCI I/O ranges Liviu Dudau
2014-09-08 13:54 ` [PATCH v10 03/10] ARM: Define PCI_IOBASE as the base of virtual PCI IO space Liviu Dudau
2014-09-08 13:54 ` [PATCH v10 04/10] PCI: OF: Fix the conversion of IO ranges into IO resources Liviu Dudau
2014-09-08 13:54 ` [PATCH v10 05/10] PCI: Create pci_host_bridge before its associated bus in pci_create_root_bus Liviu Dudau
2014-09-08 13:54 ` [PATCH v10 06/10] PCI: Introduce generic domain handling for PCI busses Liviu Dudau
2014-09-08 14:03   ` Catalin Marinas
2014-09-08 14:05     ` Liviu Dudau
2014-09-08 13:54 ` [PATCH v10 07/10] OF: Introduce helper function for getting PCI domain_nr Liviu Dudau
2014-09-08 14:27   ` Rob Herring
2014-09-08 14:54     ` Liviu Dudau
2014-09-08 15:27       ` Rob Herring
2014-09-08 15:59         ` Liviu Dudau
2014-09-08 16:39           ` Jason Gunthorpe [this message]
2014-09-09  5:54           ` Yijing Wang
2014-09-09  8:46             ` Liviu Dudau
2014-09-09  9:16               ` Arnd Bergmann
2014-09-09 11:20                 ` Catalin Marinas
2014-09-10 18:19                   ` Arnd Bergmann
2014-09-11 14:11                     ` Phil Edworthy
2014-09-11 14:49                       ` Arnd Bergmann
2014-09-09 14:17                 ` Bjorn Helgaas
2014-09-09  9:30               ` Yijing Wang
2014-09-09 14:11                 ` Liviu Dudau
2014-09-10  1:44                   ` Yijing Wang
2014-09-09 14:26                 ` Bjorn Helgaas
2014-09-09 15:41                   ` Jason Gunthorpe
2014-09-10  2:44                     ` Rob Herring
2014-09-10 16:32                       ` Jason Gunthorpe
2014-09-10  1:55                   ` Yijing Wang
2014-09-10 13:04           ` Liviu Dudau
2014-09-08 13:54 ` [PATCH v10 08/10] OF: PCI: Add support for parsing PCI host bridge resources from DT Liviu Dudau
2014-09-09 13:35   ` Lorenzo Pieralisi
2014-09-10 14:22     ` Liviu Dudau
2014-09-10 15:10       ` Lorenzo Pieralisi
2014-09-10 15:32         ` Liviu Dudau
2014-09-10 16:37           ` Lorenzo Pieralisi
2014-09-10 16:53             ` Liviu Dudau
2014-09-10 17:06               ` Lorenzo Pieralisi
2014-09-08 13:54 ` [PATCH v10 09/10] PCI: Assign unassigned bus resources in pci_scan_root_bus() Liviu Dudau
2014-09-12 10:13   ` Suravee Suthikulpanit
2014-09-12 10:34     ` Liviu Dudau
2014-09-08 13:54 ` [PATCH v10 10/10] PCI: Introduce pci_remap_iospace() for remapping PCI I/O bus resources into CPU space Liviu Dudau
2014-09-08 16:07 ` [PATCH v10 00/10] Support for creating generic PCI host bridges from DT Liviu Dudau
2014-09-12  8:25 ` Suravee Suthikulpanit
2014-09-12  9:30   ` Liviu Dudau
2014-09-12 10:00     ` Suravee Suthikulpanit

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