linux-kernel - Re: [PATCH 02/10] PCI, x86: clip firmware assigned resource under parent bridge's

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Date:	Wed, 14 Jan 2015 11:17:19 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: [PATCH 02/10] PCI, x86: clip firmware assigned resource under
 parent bridge's

On Wed, Jan 14, 2015 at 8:52 AM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> On Mon, Jan 12, 2015 at 11:23:12AM -0800, Yinghai Lu wrote:

> There's a lot of duplicated code in these patches.  Is it possible to
> factor this out a bit, e.g., something like this?
>
>   int pci_claim_bridge_resource(struct pci_dev *dev, int i)
>   {
>     if ((dev->class >> 8) != PCI_CLASS_BRIDGE_PCI)
>       return 0;
>
>     if (pci_claim_resource(dev, i) == 0)
>       return 0;         /* claimed the window */
>
>     if (!pci_bus_clip_resource(dev, i))
>       return -EINVAL;   /* clipping didn't change anything */
>
>     if (dev->subordinate)
>       pci_setup_bridge(dev->subordinate);
>     if (pci_claim_resource(dev, i) == 0)
>       return 0;         /* claimed a smaller window */
>
>     return -EINVAL;
>   }

ok. will have one in setup_bus.c

>
>>  }
>>
>>  static void pcibios_allocate_bus_resources(struct pci_bus *bus)
>> @@ -234,8 +251,12 @@ static void pcibios_allocate_bus_resources(struct pci_bus *bus)
>>       struct pci_bus *child;
>>
>>       /* Depth-First Search on bus tree */
>> -     if (bus->self)
>> -             pcibios_allocate_bridge_resources(bus->self);
>> +     if (bus->self) {
>> +             bool changed = pcibios_allocate_bridge_resources(bus->self);
>> +
>> +             if (changed)
>> +                     pci_setup_bridge(bus);
>> +     }
>>       list_for_each_entry(child, &bus->children, node)
>>               pcibios_allocate_bus_resources(child);
>>  }
>> @@ -274,18 +295,27 @@ static void pcibios_allocate_dev_resources(struct pci_dev *dev, int pass)
>>                               dev_dbg(&dev->dev,
>>                                       "BAR %d: reserving %pr (d=%d, p=%d)\n",
>>                                       idx, r, disabled, pass);
>> -                             if (pci_claim_resource(dev, idx) < 0) {
>> -                                     if (r->flags & IORESOURCE_PCI_FIXED) {
>> -                                             dev_info(&dev->dev, "BAR %d %pR is immovable\n",
>> +
>> +                             if (pci_claim_resource(dev, idx) >= 0)
>> +                                     continue;
>> +
>> +                             if (r->flags & IORESOURCE_PCI_FIXED) {
>> +                                     dev_info(&dev->dev, "BAR %d %pR is immovable\n",
>>                                                        idx, r);
>> -                                     } else {
>> -                                             /* We'll assign a new address later */
>> -                                             pcibios_save_fw_addr(dev,
>> -                                                             idx, r->start);
>> -                                             r->end -= r->start;
>> -                                             r->start = 0;
>> -                                     }
>> +                                     continue;
>> +                             }
>> +
>> +                             /* try again with clip */
>> +                             if (pci_bus_clip_resource(dev, r)) {
>> +                                     pci_update_resource(dev, idx);
>> +                                     if (pci_claim_resource(dev, idx) >= 0)
>> +                                             continue;
>
> This hunk doesn't make sense to me.  This only deals with standard BARs and
> IOV BARS.  It doesn't deal with bridge windows at all.  The sizes of these
> BARs and IOV BARs are fixed and there's no point in trying to clip them
> because we can't tell the hardware that the BAR is now smaller.
>
> It's different for bridge windows because we can adjust their size.

ok, will drop that.
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