[QUESTION] Early Write Acknowledge for PCIe configuration space

John Garry
2017-01-10T10:22:36Z

On 09/01/2017 11:52, Arnd Bergmann wrote:
> On Monday, January 9, 2017 10:59:47 AM CET John Garry wrote:
>> On 06/01/2017 11:24, Arnd Bergmann wrote:
>>> On Friday, January 6, 2017 11:15:22 AM CET John Garry wrote:
>>>
>>> Probably nobody thought about this properly in the Linux drivers. The
>>> ARMv8 ARM sounds correct here.
>>>
>>> I/O space may have the same issue, as it also requires non-posted
>>> accesses.
>>
>> Right, so our HW team's recommendation - from ARM's memory model and
>> also PCIe order model - is that not only config space but also PCIe
>> memory mapped IO has the same attribute (nE).
>
> Just to be sure we are talking about the same thing: "PCIe memory
> mapped IO" could refer to either PCI I/O space or PCI memory space.
>
> As far as I can tell, PCI memory space should *not* be using the nE
> attribute, while PCI I/O space and PCI config space should.
> Does this match what your HW team recomments?
>

Yes, right, the config and IO space recommendation is nE and memory
space is E.

In response to Will:
> What's the rationale behind that recommendation?

As Arnd said, the reasoning is that one access type is non-posted
(config and IO) and the other (memory) is posted writes.

Thanks,
John

> Arnd
>
> .
>