linux-kernel - Re: [RFC/RFT PATCH v2] PCI: move pci_read_bridge

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Date:	Fri, 12 Jun 2015 01:04:34 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
CC:	Ralf Baechle <ralf@...ux-mips.org>,
	"James E.J. Bottomley" <jejb@...isc-linux.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Richard Henderson <rth@...ddle.net>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	David Howells <dhowells@...hat.com>,
	Russell King <linux@....linux.org.uk>,
	Tony Luck <tony.luck@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	Ingo Molnar <mingo@...hat.com>,
	Michal Simek <monstr@...str.eu>,
	Chris Zankel <chris@...kel.net>, Arnd Bergmann <arnd@...db.de>,
	Krzysztof Halasa <khalasa@...p.pl>,
	Phil Edworthy <phil.edworthy@...esas.com>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Jingoo Han <jg1.han@...sung.com>,
	Lucas Stach <l.stach@...gutronix.de>,
	Simon Horman <horms@...ge.net.au>,
	Minghuan Lian <minghuan.Lian@...escale.com>,
	Murali Karicheri <m-karicheri2@...com>,
	Tanmay Inamdar <tinamdar@....com>,
	Kishon Vijay Abraham I <kishon@...com>,
	Thierry Reding <thierry.reding@...il.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Will Deacon <will.deacon@....com>,
	Jayachandran C <jchandra@...adcom.com>,
	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
Subject: Re: [RFC/RFT PATCH v2] PCI: move pci_read_bridge_bases to the generic
 PCI layer

On 06/09/2015 02:01 AM, Lorenzo Pieralisi wrote:
> When a PCI bus is scanned, upon PCI bridge detection the kernel
> has to read the bridge registers to set-up its resources so that
> the PCI resource hierarchy can be validated properly.
>
> Most if not all architectures read PCI bridge registers in the
> pcibios_fixup_bus hook, that is called by the PCI generic layer
> whenever a PCI bus is scanned.
>
> Since pci_read_bridge_bases is an arch agnostic operation (and it
> is carried out on all architectures) it can be moved to the generic
> PCI layer in order to consolidate code and remove the respective
> calls from the architectures back-ends.
>
> The PCI_PROBE_ONLY flag is not checked before calling
> pci_read_bridge_buses in the generic layer since reading the bridge
> bases is not related to resources assignment; this implies that it
> can be carried out safely on PCI_PROBE_ONLY systems too and should
> not affect architectures (alpha, mips) that check the PCI_PROBE_ONLY
> flag before reading the bridge bases.
>
> In order to validate the resource hierarchy as soon as the resources
> themselves are probed (ie read from the bridge), this patch also adds
> code to pci_read_bridge_bases that claims the bridge resources, so that
> they are validated and inserted in the resource hierarchy as soon as
> the bridge bases are probed.
>
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
> Cc: Ralf Baechle <ralf@...ux-mips.org>
> Cc: James E.J. Bottomley <jejb@...isc-linux.org>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: Richard Henderson <rth@...ddle.net>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: David Howells <dhowells@...hat.com>
> Cc: Russell King <linux@....linux.org.uk>
> Cc: Tony Luck <tony.luck@...el.com>
> Cc: David S. Miller <davem@...emloft.net>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Guenter Roeck <linux@...ck-us.net>
> Cc: Michal Simek <monstr@...str.eu>
> Cc: Chris Zankel <chris@...kel.net>

Working fine on powerpc (tested with Freescale P2020 and P5020) as well as x86
(tested on two different server class systems).

Tested-by: Guenter Roeck <linux@...ck-us.net>

Guenter

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