linux-kernel - Re: [PATCH -v11 00/30] PCI: allocate pci bus num range for unassigned bridge busn

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Date:	Thu, 3 May 2012 02:08:29 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Tony Luck <tony.luck@...el.com>,
	David Miller <davem@...emloft.net>, x86 <x86@...nel.org>,
	Dominik Brodowski <linux@...inikbrodowski.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org
Subject: Re: [PATCH -v11 00/30] PCI: allocate pci bus num range for unassigned
 bridge busn

On Wed, May 2, 2012 at 2:22 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> On Sun, Mar 18, 2012 at 11:42 PM, Yinghai Lu <yinghai@...nel.org> wrote:
>> Set up iobusn_resource tree, and register bus number range to it.
>> Later when need to find bus range, will try to allocate from the tree
>>
>> Need to test on arches other than x86. esp for ia64 and powerpc that support
>>  more than on peer root buses.
>>
>> The patches need to apply to linux v3.3 + pci-next and
>>        [PATCH -v3] PCI: pci_host_bridge related cleanup
>>
>> could be found at:
>>        git://git.kernel.org/pub/scm/linux/kernel/git/yinghai/linux-yinghai.git for-pci-busn-alloc
>
> I started merging this series, but I didn't get very far.  I stopped
> at the "resources: Add probe_resource()" patch because I don't think
> that interface makes sense yet.  My work-in-progress is at
> git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git on the
> topic/yinghai-busn-alloc branch.
>
> I *could* merge that branch, but I don't think they fix anything (that
> would come in the later patches), and there are still some issues in
> my mind.
>
>  - I think we really want a [bus 00-ff] resource for each *domain*,
> with each host bridge in the domain requesting part of that range.  I
> think these patches only track bus number usage within each host
> bridge, and I'm not sure there's any place we would detect conflicts
> between host bridges.

I updated the patch set a bit. now it have domain busn_res.

It could detect the conflicts. later could add code to resolve the conflicts.

int pci_bus_insert_busn_res(struct pci_bus *b, int bus, int bus_max)
{
        struct resource *res = &b->busn_res;
        struct resource *parent_res;
        int ret;

        res->start = bus;
        res->end = bus_max;
        res->flags = IORESOURCE_BUS;

        if (!pci_is_root_bus(b))
                parent_res = &b->parent->busn_res;
        else {
                parent_res = get_pci_domain_busn_res(pci_domain_nr(b));
                res->flags |= IORESOURCE_PCI_FIXED;
        }

        ret = insert_resource(parent_res, res);

        dev_printk(KERN_DEBUG, &b->dev,
                        "busn_res: %pR %s inserted under %s %pR\n",
                        res, ret ? "can not be" : "is",
                        pci_is_root_bus(b) ? "domain":"", parent_res);

        return ret;
}


>
>  - I think I made a mistake in the pci_create_root_bus() and
> pci_scan_root_bus() interfaces.  They currently take a bus number and
> a list of resources, and we expect the arch to include the bus number
> aperture in the list.  The bus number argument should have been
> replaced with a bus number aperture resource.  The bus number aperture
> is essential, while the MMIO/IO aperture list may be empty.  And it's
> stupid to pass both the starting bus number and a bus resource that
> contains the starting bus number.  Fixing this would make some of
> these patches quite a bit simpler.

Yes, could try to address that later to make it more clean.

>  - In some of the arches (sparc, powerpc), you added a bus number
> resource right next to existing first_busno, last_busno fields.  So
> now that data lives two places, which will bite us later.

then later we should kill first_busno and last_busno in those arches.

Yinghai
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