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

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Date:	Sun, 28 Sep 2014 16:16:21 -0500
From:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>,
	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>,
	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 09/23/2014 08:41 PM, Bjorn Helgaas wrote:
> 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

[Suravee] Liviu and I had a talk during Linaro Connect, and we came up
with a new binding for the pcie controller called "msi-parent" which is
supposed to contain phandle to the corresponded msi-controller.

>
>> 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.

[Suravee] I just sent out an RFC which implements the described binding 
here.

https://lkml.org/lkml/2014/9/28/149

Any feedback/comments are welcome :)

Thanks,

Suravee
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