linux-kernel - Re: [RFT PATCH v3] PCI: move pci_read_bridge

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Message-ID: <55AFA741.2010703@roeck-us.net>
Date:	Wed, 22 Jul 2015 07:22:57 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pci@...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@....com" <suravee.suthikulpanit@....com>
Subject: Re: [RFT PATCH v3] PCI: move pci_read_bridge_bases to the generic
 PCI layer

On 07/22/2015 02:14 AM, Lorenzo Pieralisi wrote:
> Bjorn, Guenter,
>
> On Thu, Jul 09, 2015 at 11:59:16AM +0100, 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.
>>
>> 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>
>> ---
>> v2->v3:
>>
>> - Dropped RFC status
>> - Removed bridge resources claiming from pci_read_bridge_bases()
>
> What do you want me to do with this patch ? I removed the resource
> claiming - ie the only controversial bit, I can only test on
> arm64, I would like to make some progress on this otherwise
> I will have to add the bridge bases read to arm64 pcibios_fixup_bus()
> and be done with this.
>

Lorenzo,

please give me a few days to test it. I was out on vacation for
the last two weeks, and I am still struggling to get my test systems
back to a working state.

Thanks,
Guenter

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