Re: [Resend PATCH 5/5] IA64/PCI/ACPI: Rework PCI root bridge ACPIresource conversion

[Lan Tianyu]

On 2013å10æ29æ 01:32, Bjorn Helgaas wrote:
> On Sat, Oct 26, 2013 at 10:53 AM, Lan Tianyu <tianyu.lan@xxxxxxxxx> 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.

Yes, my concern is for the IO resource case of _TTP=0 and _TRA !=0. The
only reason for this case I think of is that the IO resource offsets on
the prime bus and second bus are different. In this case, we still need
to pass _TRA to new_space() and the finial resource->start still should 
be acpi_resource->min + offset returned by add_io_space(), right?

If yes, I think _TRA can't be applied to IO resource in the
acpi_dev_resource_address_space() regardless of the value of _TTP.

BTW, Translation Sparse(_TRS) is only meaningful if _TTP is set.(Table 
6-185). The add_io_space() doesn't check _TTP when set sparse. So this 
should be corrected?

> Bjorn


--
Best regards
Tianyu Lan
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/