linux-kernel - Re: [Resend PATCH 5/5] IA64/PCI/ACPI: Rework PCI root bridge ACPI resource conversion

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Date:	Mon, 28 Oct 2013 11:32:30 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Lan Tianyu <tianyu.lan@...el.com>
Cc:	Tony Luck <tony.luck@...el.com>, Len Brown <lenb@...nel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Yinghai Lu <yinghai@...nel.org>,
	"linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"Yoknis, Mike" <mike.yoknis@...com>,
	"Pearson, Greg" <greg.pearson@...com>
Subject: Re: [Resend PATCH 5/5] IA64/PCI/ACPI: Rework PCI root bridge ACPI
 resource conversion

On Sat, Oct 26, 2013 at 10:53 AM, Lan Tianyu <tianyu.lan@...el.com> wrote:
> On 10/24/2013 06:39 AM, Bjorn Helgaas wrote:
>> On Fri, Oct 18, 2013 at 08:44:12PM +0800, Lan Tianyu wrote:
>>>
>>> On 10/18/2013 04:33 AM, Bjorn Helgaas wrote:

>>>> I wonder if it would make sense to make
>>>> acpi_dev_resource_address_space() ignore addr.translation_offset for
>>>> IO resources.  Or maybe ignore it if the _TTP (type translation) bit
>>>> is set?
>>>
>>>
>>> I wonder why current code doesn't check _TTP? The code in the
>>> add_io_space() seems to think _TTP is always set, right?
>>
>> I think it's an oversight, and you should fix it.  I suggest that you
>> ignore the _TRA value when _TTP is set.  Obviously this only applies
>> to I/O port resources, since _TTP is only defined in the I/O Resource
>> Flag (Table 6-185 in ACPI 5.0 spec).
>
> _TTP is also defined in the Memory Resource flag, Please have a look at
> Table 6-184 in the ACPI 5.0 Spec.

Yes, you're right.  That would be for a host bridge that converts I/O
on the primary (upstream) side of the bridge to memory on the PCI
side.  I've never seen such a bridge, and I can't really imagine why
anybody would do that.  But I guess you should be able to safely
ignore _TRA when _TTP is set in either a MEM or IO descriptor, because
the same reasoning should apply to both.

> I am not sure how to deal with _TTP unsetting io resource? _TTP unsetting
> mean the resource is IO on the primary side and also IO on the secondary
> side.

If _TTP is not set, I guess you would apply _TRA.  That's what you
already do for MEM descriptors, and think you should just do the same
for IO descriptors.  I would guess that having _TTP = 0 and _TRA != 0
is rare for IO descriptors, but I suppose it could happen.

Bjorn
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