linux-kernel - Re: [PATCH v12 10/12] PCI: Assign unassigned bus resources in pci_scan_root

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Message-ID: <CAErSpo5DR+TPYXBWGKRj9SRPjsbJ6kjZmAH1AXT12txEjGdZGQ@mail.gmail.com>
Date:	Tue, 23 Sep 2014 19:41:35 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Liviu Dudau <liviu@...au.co.uk>
Cc:	Liviu Dudau <Liviu.Dudau@....com>, Arnd Bergmann <arnd@...db.de>,
	Rob Herring <robh+dt@...nel.org>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	Russell King <linux@....linux.org.uk>,
	linux-pci <linux-pci@...r.kernel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Tanmay Inamdar <tinamdar@....com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Sinan Kaya <okaya@...eaurora.org>,
	Jingoo Han <jg1.han@...sung.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Suravee Suthikulanit <suravee.suthikulpanit@....com>,
	linux-arch <linux-arch@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Device Tree ML <devicetree@...r.kernel.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v12 10/12] PCI: Assign unassigned bus resources in pci_scan_root_bus()

On Tue, Sep 23, 2014 at 7:18 PM, Liviu Dudau <liviu@...au.co.uk> wrote:
> On Tue, Sep 23, 2014 at 08:01:12PM +0100, Liviu Dudau wrote:
>> If the firmware has not assigned all the bus resources and
>> we are not just probing the PCIe busses, it makes sense to
>> assign the unassigned resources in pci_scan_root_bus().
>>
>> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
>> Cc: Arnd Bergmann <arnd@...db.de>
>> Cc: Jason Gunthorpe <jgunthorpe@...idianresearch.com>
>> Cc: Rob Herring <robh+dt@...nel.org>
>> Signed-off-by: Liviu Dudau <Liviu.Dudau@....com>
>> ---
>>  drivers/pci/probe.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
>> index ef891d2..508cf61 100644
>> --- a/drivers/pci/probe.c
>> +++ b/drivers/pci/probe.c
>> @@ -1953,6 +1953,9 @@ struct pci_bus *pci_scan_root_bus(struct device *parent, int bus,
>>       if (!found)
>>               pci_bus_update_busn_res_end(b, max);
>>
>> +     if (!pci_has_flag(PCI_PROBE_ONLY))
>> +             pci_assign_unassigned_bus_resources(b);
>> +
>>       pci_bus_add_devices(b);
>>       return b;
>>  }
>> --
>> 2.1.0
>>
>
> Bjorn,
>
> If you are OK with this patch, can you let me know how do you feel about
> making pci_scan_root_bus() set up the bus->msi pointer as well?

I'm not opposed to it, but I have the same question as for setting up
the domain: how does pci_scan_root_bus() learn what to assign to
bus->msi?  It currently only gets a "void *sysdata" so there's no
obvious place to put it there.  You could add a pcibios interface to
retrieve it, I suppose, but I'm starting to get uncomfortable with
adding more of those because we have such a mess of them already.

Bjorn

> Side note: I don't know exactly how to do it now, but setting bus->msi is
> needed by platforms that are based on my patches and want to use MSI,
> otherwise they have to open code pci_scan_root_bus() to set it. I haven't
> made any attempts to do it in this series as the GICv2m patches are not
> ready yet, but I can see the need arriving soon.
>
> Best regards,
> Liviu
>
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>
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