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

[Lan Tianyu <tianyu.lan@intel.com>]

On 2013年10月31日 00:23, Bjorn Helgaas wrote:
> On Wed, Oct 30, 2013 at 2:34 AM, Lan Tianyu <tianyu.lan@intel.com> wrote:
>> On 2013年10月29日 01:32, Bjorn Helgaas wrote:
>>>
>>> On Sat, Oct 26, 2013 at 10:53 AM, Lan Tianyu <tianyu.lan@intel.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.
>>
>>
>> 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?
> 
> No, I don't think so.  If the "phys_base" argument to new_space() is
> non-zero, it is the base of an MMIO region that needs to be
> ioremapped.  This is handling the _TTP=1 case, where the MMIO region
> is translated by the bridge into an IO region on PCI.
> 
> If _TTP=0, the region is IO on both the upstream and downstream sides
> of the host bridge, and we don't want to ioremap a new MMIO region for
> it.  It might be part of the "legacy I/O port space," but that's
> already covered elsewhere.
> 
> I don't think we need to add special handling for the _TTP=0 and _TRA
> != 0 case because I don't think it exists in the field.  If and when
> it *does* exist, we'll know what to do.  In the meantime, it should
> look just like the MEM path.


OK. I get it. acpi_dev_resource_address_space() will only apply _TRA to
resource ->start and ->end for both mem and io resource when _TTP=0. In
the add_window(), the offset returned by add_io_space() will be added
directly to ->start and ->end.

add_window() {
	...
	if (resource->flags & IORESOURCE_MEM) {
		root = &iomem_resource;
		offset = addr.translation_offset;
	} else if (resource->flags & IORESOURCE_IO) {
		root = &ioport_resource;

		offset = add_io_space(info, &addr);
		if (offset == ~0)
			return AE_OK;

		resource->start += offset;
		resource->end += offset;
	} else
		return AE_OK;

	...
}

> 
>> 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?
> 
> Sure, I'm OK with this.  It's possible we could trip over a BIOS bug
> where _TRS=1 but _TTP=0, but I think the risk is low because only
> large ia64 boxes would use this, and there aren't very many of those.
> 

Ok. I will add a check for _TTP before setting sparse. Something likes this.

add_io_space()
{
...
if (addr->info.io.translation == ACPI_TYPE_TRANSLATION &&
    addr->info.io.translation_type == ACPI_SPARSE_TRANSLATION)
	sparse = 1;
...
}



> Bjorn
> 


-- 
Best regards
Tianyu Lan
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